SCSI Interfaces Guide¶
Author: | James Bottomley |
---|---|
Author: | Rob Landley |
Introduction¶
Protocol vs bus¶
Once upon a time, the Small Computer Systems Interface defined both a parallel I/O bus and a data protocol to connect a wide variety of peripherals (disk drives, tape drives, modems, printers, scanners, optical drives, test equipment, and medical devices) to a host computer.
Although the old parallel (fast/wide/ultra) SCSI bus has largely fallen out of use, the SCSI command set is more widely used than ever to communicate with devices over a number of different busses.
The SCSI protocol is a big-endian peer-to-peer packet based protocol. SCSI commands are 6, 10, 12, or 16 bytes long, often followed by an associated data payload.
SCSI commands can be transported over just about any kind of bus, and are the default protocol for storage devices attached to USB, SATA, SAS, Fibre Channel, FireWire, and ATAPI devices. SCSI packets are also commonly exchanged over Infiniband, I20, TCP/IP (iSCSI), even Parallel ports.
Design of the Linux SCSI subsystem¶
The SCSI subsystem uses a three layer design, with upper, mid, and low layers. Every operation involving the SCSI subsystem (such as reading a sector from a disk) uses one driver at each of the 3 levels: one upper layer driver, one lower layer driver, and the SCSI midlayer.
The SCSI upper layer provides the interface between userspace and the kernel, in the form of block and char device nodes for I/O and ioctl(). The SCSI lower layer contains drivers for specific hardware devices.
In between is the SCSI mid-layer, analogous to a network routing layer such as the IPv4 stack. The SCSI mid-layer routes a packet based data protocol between the upper layer’s /dev nodes and the corresponding devices in the lower layer. It manages command queues, provides error handling and power management functions, and responds to ioctl() requests.
SCSI upper layer¶
The upper layer supports the user-kernel interface by providing device nodes.
sd (SCSI Disk)¶
sd (sd_mod.o)
sr (SCSI CD-ROM)¶
sr (sr_mod.o)
st (SCSI Tape)¶
st (st.o)
sg (SCSI Generic)¶
sg (sg.o)
ch (SCSI Media Changer)¶
ch (ch.c)
SCSI mid layer¶
SCSI midlayer implementation¶
include/scsi/scsi_device.h¶
-
shost_for_each_device
(sdev, shost)¶ iterate over all devices of a host
Parameters
sdev
- the
struct scsi_device
to use as a cursor shost
- the
struct scsi_host
to iterate over
Description
Iterator that returns each device attached to shost. This loop takes a reference on each device and releases it at the end. If you break out of the loop, you must call scsi_device_put(sdev).
-
__shost_for_each_device
(sdev, shost)¶ iterate over all devices of a host (UNLOCKED)
Parameters
sdev
- the
struct scsi_device
to use as a cursor shost
- the
struct scsi_host
to iterate over
Description
Iterator that returns each device attached to shost. It does _not_ take a reference on the scsi_device, so the whole loop must be protected by shost->host_lock.
Note
The only reason to use this is because you need to access the device list in interrupt context. Otherwise you really want to use shost_for_each_device instead.
-
int
scsi_device_supports_vpd
(struct scsi_device * sdev)¶ test if a device supports VPD pages
Parameters
struct scsi_device * sdev
- the
struct scsi_device
to test
Description
If the ‘try_vpd_pages’ flag is set it takes precedence. Otherwise we will assume VPD pages are supported if the SCSI level is at least SPC-3 and ‘skip_vpd_pages’ is not set.
drivers/scsi/scsi.c¶
Main file for the SCSI midlayer.
-
void
scsi_cmd_get_serial
(struct Scsi_Host * host, struct scsi_cmnd * cmd)¶ Assign a serial number to a command
Parameters
struct Scsi_Host * host
- the scsi host
struct scsi_cmnd * cmd
- command to assign serial number to
Description
a serial number identifies a request for error recovery and debugging purposes. Protected by the Host_Lock of host.
-
int
scsi_change_queue_depth
(struct scsi_device * sdev, int depth)¶ change a device’s queue depth
Parameters
struct scsi_device * sdev
- SCSI Device in question
int depth
- number of commands allowed to be queued to the driver
Description
Sets the device queue depth and returns the new value.
-
int
scsi_track_queue_full
(struct scsi_device * sdev, int depth)¶ track QUEUE_FULL events to adjust queue depth
Parameters
struct scsi_device * sdev
- SCSI Device in question
int depth
- Current number of outstanding SCSI commands on this device, not counting the one returned as QUEUE_FULL.
Description
- This function will track successive QUEUE_FULL events on a
- specific SCSI device to determine if and when there is a need to adjust the queue depth on the device.
Return
- 0 - No change needed, >0 - Adjust queue depth to this new depth,
- -1 - Drop back to untagged operation using host->cmd_per_lun
- as the untagged command depth
Lock Status: None held on entry
Notes
- Low level drivers may call this at any time and we will do
- “The Right Thing.” We are interrupt context safe.
-
int
scsi_get_vpd_page
(struct scsi_device * sdev, u8 page, unsigned char * buf, int buf_len)¶ Get Vital Product Data from a SCSI device
Parameters
struct scsi_device * sdev
- The device to ask
u8 page
- Which Vital Product Data to return
unsigned char * buf
- where to store the VPD
int buf_len
- number of bytes in the VPD buffer area
Description
SCSI devices may optionally supply Vital Product Data. Each ‘page’
of VPD is defined in the appropriate SCSI document (eg SPC, SBC).
If the device supports this VPD page, this routine returns a pointer
to a buffer containing the data from that page. The caller is
responsible for calling kfree()
on this pointer when it is no longer
needed. If we cannot retrieve the VPD page this routine returns NULL
.
-
int
scsi_report_opcode
(struct scsi_device * sdev, unsigned char * buffer, unsigned int len, unsigned char opcode)¶ Find out if a given command opcode is supported
Parameters
struct scsi_device * sdev
- scsi device to query
unsigned char * buffer
- scratch buffer (must be at least 20 bytes long)
unsigned int len
- length of buffer
unsigned char opcode
- opcode for command to look up
Description
Uses the REPORT SUPPORTED OPERATION CODES to look up the given opcode. Returns -EINVAL if RSOC fails, 0 if the command opcode is unsupported and 1 if the device claims to support the command.
-
int
scsi_device_get
(struct scsi_device * sdev)¶ get an additional reference to a scsi_device
Parameters
struct scsi_device * sdev
- device to get a reference to
Description
Gets a reference to the scsi_device and increments the use count of the underlying LLDD module. You must hold host_lock of the parent Scsi_Host or already have a reference when calling this.
This will fail if a device is deleted or cancelled, or when the LLD module is in the process of being unloaded.
-
void
scsi_device_put
(struct scsi_device * sdev)¶ release a reference to a scsi_device
Parameters
struct scsi_device * sdev
- device to release a reference on.
Description
Release a reference to the scsi_device and decrements the use count of the underlying LLDD module. The device is freed once the last user vanishes.
-
void
starget_for_each_device
(struct scsi_target * starget, void * data, void (*fn) (struct scsi_device *, void *)¶ helper to walk all devices of a target
Parameters
struct scsi_target * starget
- target whose devices we want to iterate over.
void * data
- Opaque passed to each function call.
void (*)(struct scsi_device *, void *) fn
- Function to call on each device
Description
This traverses over each device of starget. The devices have a reference that must be released by scsi_host_put when breaking out of the loop.
-
void
__starget_for_each_device
(struct scsi_target * starget, void * data, void (*fn) (struct scsi_device *, void *)¶ helper to walk all devices of a target (UNLOCKED)
Parameters
struct scsi_target * starget
- target whose devices we want to iterate over.
void * data
- parameter for callback fn()
void (*)(struct scsi_device *, void *) fn
- callback function that is invoked for each device
Description
This traverses over each device of starget. It does _not_ take a reference on the scsi_device, so the whole loop must be protected by shost->host_lock.
Note
The only reason why drivers would want to use this is because they need to access the device list in irq context. Otherwise you really want to use starget_for_each_device instead.
-
struct scsi_device *
__scsi_device_lookup_by_target
(struct scsi_target * starget, u64 lun)¶ find a device given the target (UNLOCKED)
Parameters
struct scsi_target * starget
- SCSI target pointer
u64 lun
- SCSI Logical Unit Number
Description
Looks up the scsi_device with the specified lun for a given starget. The returned scsi_device does not have an additional reference. You must hold the host’s host_lock over this call and any access to the returned scsi_device. A scsi_device in state SDEV_DEL is skipped.
Note
The only reason why drivers should use this is because they need to access the device list in irq context. Otherwise you really want to use scsi_device_lookup_by_target instead.
-
struct scsi_device *
scsi_device_lookup_by_target
(struct scsi_target * starget, u64 lun)¶ find a device given the target
Parameters
struct scsi_target * starget
- SCSI target pointer
u64 lun
- SCSI Logical Unit Number
Description
Looks up the scsi_device with the specified lun for a given starget. The returned scsi_device has an additional reference that needs to be released with scsi_device_put once you’re done with it.
-
struct scsi_device *
__scsi_device_lookup
(struct Scsi_Host * shost, uint channel, uint id, u64 lun)¶ find a device given the host (UNLOCKED)
Parameters
struct Scsi_Host * shost
- SCSI host pointer
uint channel
- SCSI channel (zero if only one channel)
uint id
- SCSI target number (physical unit number)
u64 lun
- SCSI Logical Unit Number
Description
Looks up the scsi_device with the specified channel, id, lun for a given host. The returned scsi_device does not have an additional reference. You must hold the host’s host_lock over this call and any access to the returned scsi_device.
Note
The only reason why drivers would want to use this is because they need to access the device list in irq context. Otherwise you really want to use scsi_device_lookup instead.
-
struct scsi_device *
scsi_device_lookup
(struct Scsi_Host * shost, uint channel, uint id, u64 lun)¶ find a device given the host
Parameters
struct Scsi_Host * shost
- SCSI host pointer
uint channel
- SCSI channel (zero if only one channel)
uint id
- SCSI target number (physical unit number)
u64 lun
- SCSI Logical Unit Number
Description
Looks up the scsi_device with the specified channel, id, lun for a given host. The returned scsi_device has an additional reference that needs to be released with scsi_device_put once you’re done with it.
drivers/scsi/scsicam.c¶
SCSI Common Access Method support functions, for use with HDIO_GETGEO, etc.
-
unsigned char *
scsi_bios_ptable
(struct block_device * dev)¶ Read PC partition table out of first sector of device.
Parameters
struct block_device * dev
- from this device
Description
- Reads the first sector from the device and returns
0x42
bytes - starting at offset
0x1be
.
Return
partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
-
int
scsicam_bios_param
(struct block_device * bdev, sector_t capacity, int * ip)¶ Determine geometry of a disk in cylinders/heads/sectors.
Parameters
struct block_device * bdev
- which device
sector_t capacity
- size of the disk in sectors
int * ip
- return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
Description
- determine the BIOS mapping/geometry used for a drive in a
- SCSI-CAM system, storing the results in ip as required
by the HDIO_GETGEO
ioctl()
.
Return
-1 on failure, 0 on success.
-
int
scsi_partsize
(unsigned char * buf, unsigned long capacity, unsigned int * cyls, unsigned int * hds, unsigned int * secs)¶ Parse cylinders/heads/sectors from PC partition table
Parameters
unsigned char * buf
- partition table, see
scsi_bios_ptable()
unsigned long capacity
- size of the disk in sectors
unsigned int * cyls
- put cylinders here
unsigned int * hds
- put heads here
unsigned int * secs
- put sectors here
Description
Determine the BIOS mapping/geometry used to create the partition table, storing the results in cyls, hds, and secs
Return
-1 on failure, 0 on success.
drivers/scsi/scsi_error.c¶
Common SCSI error/timeout handling routines.
-
void
scsi_schedule_eh
(struct Scsi_Host * shost)¶ schedule EH for SCSI host
Parameters
struct Scsi_Host * shost
- SCSI host to invoke error handling on.
Description
Schedule SCSI EH without scmd.
-
int
scsi_block_when_processing_errors
(struct scsi_device * sdev)¶ Prevent cmds from being queued.
Parameters
struct scsi_device * sdev
- Device on which we are performing recovery.
Description
We block until the host is out of error recovery, and then check to see whether the host or the device is offline.
- Return value:
- 0 when dev was taken offline by error recovery. 1 OK to proceed.
-
int
scsi_check_sense
(struct scsi_cmnd * scmd)¶ Examine scsi cmd sense
Parameters
struct scsi_cmnd * scmd
- Cmd to have sense checked.
Description
- Return value:
- SUCCESS or FAILED or NEEDS_RETRY or ADD_TO_MLQUEUE
Notes
When a deferred error is detected the current command has not been executed and needs retrying.
-
void
scsi_eh_prep_cmnd
(struct scsi_cmnd * scmd, struct scsi_eh_save * ses, unsigned char * cmnd, int cmnd_size, unsigned sense_bytes)¶ Save a scsi command info as part of error recovery
Parameters
struct scsi_cmnd * scmd
- SCSI command structure to hijack
struct scsi_eh_save * ses
- structure to save restore information
unsigned char * cmnd
- CDB to send. Can be NULL if no new cmnd is needed
int cmnd_size
- size in bytes of cmnd (must be <= BLK_MAX_CDB)
unsigned sense_bytes
- size of sense data to copy. or 0 (if != 0 cmnd is ignored)
Description
This function is used to save a scsi command information before re-execution as part of the error recovery process. If sense_bytes is 0 the command sent must be one that does not transfer any data. If sense_bytes != 0 cmnd is ignored and this functions sets up a REQUEST_SENSE command and cmnd buffers to read sense_bytes into scmd->sense_buffer.
-
void
scsi_eh_restore_cmnd
(struct scsi_cmnd * scmd, struct scsi_eh_save * ses)¶ Restore a scsi command info as part of error recovery
Parameters
struct scsi_cmnd * scmd
- SCSI command structure to restore
struct scsi_eh_save * ses
- saved information from a coresponding call to scsi_eh_prep_cmnd
Description
Undo any damage done by above scsi_eh_prep_cmnd()
.
-
void
scsi_eh_finish_cmd
(struct scsi_cmnd * scmd, struct list_head * done_q)¶ Handle a cmd that eh is finished with.
Parameters
struct scsi_cmnd * scmd
- Original SCSI cmd that eh has finished.
struct list_head * done_q
- Queue for processed commands.
Notes
We don’t want to use the normal command completion while we are are still handling errors - it may cause other commands to be queued, and that would disturb what we are doing. Thus we really want to keep a list of pending commands for final completion, and once we are ready to leave error handling we handle completion for real.
-
int
scsi_eh_get_sense
(struct list_head * work_q, struct list_head * done_q)¶ Get device sense data.
Parameters
struct list_head * work_q
- Queue of commands to process.
struct list_head * done_q
- Queue of processed commands.
Description
See if we need to request sense information. if so, then get it now, so we have a better idea of what to do.
Notes
This has the unfortunate side effect that if a shost adapter does not automatically request sense information, we end up shutting it down before we request it.
All drivers should request sense information internally these days, so for now all I have to say is tough noogies if you end up in here.
- XXX: Long term this code should go away, but that needs an audit of
- all LLDDs first.
-
void
scsi_eh_ready_devs
(struct Scsi_Host * shost, struct list_head * work_q, struct list_head * done_q)¶ check device ready state and recover if not.
Parameters
struct Scsi_Host * shost
- host to be recovered.
struct list_head * work_q
list_head
for pending commands.struct list_head * done_q
list_head
for processed commands.
-
void
scsi_eh_flush_done_q
(struct list_head * done_q)¶ finish processed commands or retry them.
Parameters
struct list_head * done_q
- list_head of processed commands.
-
int
scsi_ioctl_reset
(struct scsi_device * dev, int __user * arg)¶
Parameters
struct scsi_device * dev
- scsi_device to operate on
int __user * arg
- reset type (see sg.h)
-
bool
scsi_get_sense_info_fld
(const u8 * sense_buffer, int sb_len, u64 * info_out)¶ get information field from sense data (either fixed or descriptor format)
Parameters
const u8 * sense_buffer
- byte array of sense data
int sb_len
- number of valid bytes in sense_buffer
u64 * info_out
- pointer to 64 integer where 8 or 4 byte information field will be placed if found.
Description
- Return value:
- true if information field found, false if not found.
drivers/scsi/scsi_devinfo.c¶
Manage scsi_dev_info_list, which tracks blacklisted and whitelisted devices.
-
int
scsi_dev_info_list_add
(int compatible, char * vendor, char * model, char * strflags, int flags)¶ add one dev_info list entry.
Parameters
int compatible
- if true, null terminate short strings. Otherwise space pad.
char * vendor
- vendor string
char * model
- model (product) string
char * strflags
- integer string
int flags
- if strflags NULL, use this flag value
Description
Create and add one dev_info entry for vendor, model, strflags or flag. If compatible, add to the tail of the list, do not space pad, and set devinfo->compatible. The scsi_static_device_list entries are added with compatible 1 and clfags NULL.
Return
0 OK, -error on failure.
-
struct scsi_dev_info_list *
scsi_dev_info_list_find
(const char * vendor, const char * model, int key)¶ find a matching dev_info list entry.
Parameters
const char * vendor
- vendor string
const char * model
- model (product) string
int key
- specify list to use
Description
Finds the first dev_info entry matching vendor, model in list specified by key.
Return
pointer to matching entry, or ERR_PTR on failure.
-
int
scsi_dev_info_list_add_str
(char * dev_list)¶ parse dev_list and add to the scsi_dev_info_list.
Parameters
char * dev_list
- string of device flags to add
Description
Parse dev_list, and add entries to the scsi_dev_info_list. dev_list is of the form “vendor:product:flag,vendor:product:flag”. dev_list is modified via strsep. Can be called for command line addition, for proc or mabye a sysfs interface.
Return
0 if OK, -error on failure.
-
int
scsi_get_device_flags
(struct scsi_device * sdev, const unsigned char * vendor, const unsigned char * model)¶ get device specific flags from the dynamic device list.
Parameters
struct scsi_device * sdev
scsi_device
to get flags forconst unsigned char * vendor
- vendor name
const unsigned char * model
- model name
Description
Search the global scsi_dev_info_list (specified by list zero) for an entry matching vendor and model, if found, return the matching flags value, else return the host or global default settings. Called during scan time.
-
void
scsi_exit_devinfo
(void)¶ remove /proc/scsi/device_info & the scsi_dev_info_list
Parameters
void
- no arguments
-
int
scsi_init_devinfo
(void)¶ set up the dynamic device list.
Parameters
void
- no arguments
Description
Add command line entries from scsi_dev_flags, then add scsi_static_device_list entries to the scsi device info list.
drivers/scsi/scsi_ioctl.c¶
Handle ioctl() calls for SCSI devices.
-
int
scsi_ioctl
(struct scsi_device * sdev, int cmd, void __user * arg)¶ Dispatch ioctl to scsi device
Parameters
struct scsi_device * sdev
- scsi device receiving ioctl
int cmd
- which ioctl is it
void __user * arg
- data associated with ioctl
Description
The scsi_ioctl()
function differs from most ioctls in that it
does not take a major/minor number as the dev field. Rather, it takes
a pointer to a struct scsi_device
.
drivers/scsi/scsi_lib.c¶
SCSI queuing library.
-
int
scsi_execute
(struct scsi_device * sdev, const unsigned char * cmd, int data_direction, void * buffer, unsigned bufflen, unsigned char * sense, struct scsi_sense_hdr * sshdr, int timeout, int retries, u64 flags, req_flags_t rq_flags, int * resid)¶ insert request and wait for the result
Parameters
struct scsi_device * sdev
- scsi device
const unsigned char * cmd
- scsi command
int data_direction
- data direction
void * buffer
- data buffer
unsigned bufflen
- len of buffer
unsigned char * sense
- optional sense buffer
struct scsi_sense_hdr * sshdr
- optional decoded sense header
int timeout
- request timeout in seconds
int retries
- number of times to retry request
u64 flags
- flags for ->cmd_flags
req_flags_t rq_flags
- flags for ->rq_flags
int * resid
- optional residual length
Description
Returns the scsi_cmnd result field if a command was executed, or a negative Linux error code if we didn’t get that far.
-
void
scsi_initialize_rq
(struct request * rq)¶ initialize struct scsi_cmnd.req
Parameters
struct request * rq
- undescribed
Description
Called from inside blk_get_request()
.
-
struct scsi_device *
scsi_device_from_queue
(struct request_queue * q)¶ return sdev associated with a request_queue
Parameters
struct request_queue * q
- The request queue to return the sdev from
Description
Return the sdev associated with a request queue or NULL if the request_queue does not reference a SCSI device.
-
int
scsi_mode_select
(struct scsi_device * sdev, int pf, int sp, int modepage, unsigned char * buffer, int len, int timeout, int retries, struct scsi_mode_data * data, struct scsi_sense_hdr * sshdr)¶ issue a mode select
Parameters
struct scsi_device * sdev
- SCSI device to be queried
int pf
- Page format bit (1 == standard, 0 == vendor specific)
int sp
- Save page bit (0 == don’t save, 1 == save)
int modepage
- mode page being requested
unsigned char * buffer
- request buffer (may not be smaller than eight bytes)
int len
- length of request buffer.
int timeout
- command timeout
int retries
- number of retries before failing
struct scsi_mode_data * data
- returns a structure abstracting the mode header data
struct scsi_sense_hdr * sshdr
- place to put sense data (or NULL if no sense to be collected). must be SCSI_SENSE_BUFFERSIZE big.
Description
Returns zero if successful; negative error number or scsi status on error
-
int
scsi_mode_sense
(struct scsi_device * sdev, int dbd, int modepage, unsigned char * buffer, int len, int timeout, int retries, struct scsi_mode_data * data, struct scsi_sense_hdr * sshdr)¶ issue a mode sense, falling back from 10 to six bytes if necessary.
Parameters
struct scsi_device * sdev
- SCSI device to be queried
int dbd
- set if mode sense will allow block descriptors to be returned
int modepage
- mode page being requested
unsigned char * buffer
- request buffer (may not be smaller than eight bytes)
int len
- length of request buffer.
int timeout
- command timeout
int retries
- number of retries before failing
struct scsi_mode_data * data
- returns a structure abstracting the mode header data
struct scsi_sense_hdr * sshdr
- place to put sense data (or NULL if no sense to be collected). must be SCSI_SENSE_BUFFERSIZE big.
Description
Returns zero if unsuccessful, or the header offset (either 4 or 8 depending on whether a six or ten byte command was issued) if successful.
-
int
scsi_test_unit_ready
(struct scsi_device * sdev, int timeout, int retries, struct scsi_sense_hdr * sshdr)¶ test if unit is ready
Parameters
struct scsi_device * sdev
- scsi device to change the state of.
int timeout
- command timeout
int retries
- number of retries before failing
struct scsi_sense_hdr * sshdr
- outpout pointer for decoded sense information.
Description
Returns zero if unsuccessful or an error if TUR failed. For removable media, UNIT_ATTENTION sets ->changed flag.
-
int
scsi_device_set_state
(struct scsi_device * sdev, enum scsi_device_state state)¶ Take the given device through the device state model.
Parameters
struct scsi_device * sdev
- scsi device to change the state of.
enum scsi_device_state state
- state to change to.
Description
Returns zero if unsuccessful or an error if the requested transition is illegal.
-
void
sdev_evt_send
(struct scsi_device * sdev, struct scsi_event * evt)¶ send asserted event to uevent thread
Parameters
struct scsi_device * sdev
- scsi_device event occurred on
struct scsi_event * evt
- event to send
Description
Assert scsi device event asynchronously.
-
struct scsi_event *
sdev_evt_alloc
(enum scsi_device_event evt_type, gfp_t gfpflags)¶ allocate a new scsi event
Parameters
enum scsi_device_event evt_type
- type of event to allocate
gfp_t gfpflags
- GFP flags for allocation
Description
Allocates and returns a new scsi_event.
-
void
sdev_evt_send_simple
(struct scsi_device * sdev, enum scsi_device_event evt_type, gfp_t gfpflags)¶ send asserted event to uevent thread
Parameters
struct scsi_device * sdev
- scsi_device event occurred on
enum scsi_device_event evt_type
- type of event to send
gfp_t gfpflags
- GFP flags for allocation
Description
Assert scsi device event asynchronously, given an event type.
-
int
scsi_device_quiesce
(struct scsi_device * sdev)¶ Block user issued commands.
Parameters
struct scsi_device * sdev
- scsi device to quiesce.
Description
This works by trying to transition to the SDEV_QUIESCE state (which must be a legal transition). When the device is in this state, only special requests will be accepted, all others will be deferred. Since special requests may also be requeued requests, a successful return doesn’t guarantee the device will be totally quiescent.
Must be called with user context, may sleep.
Returns zero if unsuccessful or an error if not.
-
void
scsi_device_resume
(struct scsi_device * sdev)¶ Restart user issued commands to a quiesced device.
Parameters
struct scsi_device * sdev
- scsi device to resume.
Description
Moves the device from quiesced back to running and restarts the queues.
Must be called with user context, may sleep.
-
int
scsi_internal_device_block_nowait
(struct scsi_device * sdev)¶ try to transition to the SDEV_BLOCK state
Parameters
struct scsi_device * sdev
- device to block
Description
Pause SCSI command processing on the specified device. Does not sleep.
Returns zero if successful or a negative error code upon failure.
Notes
This routine transitions the device to the SDEV_BLOCK state (which must be
a legal transition). When the device is in this state, command processing
is paused until the device leaves the SDEV_BLOCK state. See also
scsi_internal_device_unblock_nowait()
.
-
int
scsi_internal_device_unblock_nowait
(struct scsi_device * sdev, enum scsi_device_state new_state)¶ resume a device after a block request
Parameters
struct scsi_device * sdev
- device to resume
enum scsi_device_state new_state
- state to set the device to after unblocking
Description
Restart the device queue for a previously suspended SCSI device. Does not sleep.
Returns zero if successful or a negative error code upon failure.
Notes
This routine transitions the device to the SDEV_RUNNING state or to one of the offline states (which must be a legal transition) allowing the midlayer to goose the queue for this device.
-
void *
scsi_kmap_atomic_sg
(struct scatterlist * sgl, int sg_count, size_t * offset, size_t * len)¶ find and atomically map an sg-elemnt
Parameters
struct scatterlist * sgl
- scatter-gather list
int sg_count
- number of segments in sg
size_t * offset
- offset in bytes into sg, on return offset into the mapped area
size_t * len
- bytes to map, on return number of bytes mapped
Description
Returns virtual address of the start of the mapped page
-
void
scsi_kunmap_atomic_sg
(void * virt)¶ atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
Parameters
void * virt
- virtual address to be unmapped
-
int
scsi_vpd_lun_id
(struct scsi_device * sdev, char * id, size_t id_len)¶ return a unique device identification
Parameters
struct scsi_device * sdev
- SCSI device
char * id
- buffer for the identification
size_t id_len
- length of the buffer
Description
Copies a unique device identification into id based on the information in the VPD page 0x83 of the device. The string will be formatted as a SCSI name string.
Returns the length of the identification or error on failure. If the identifier is longer than the supplied buffer the actual identifier length is returned and the buffer is not zero-padded.
drivers/scsi/scsi_lib_dma.c¶
SCSI library functions depending on DMA (map and unmap scatter-gather lists).
-
int
scsi_dma_map
(struct scsi_cmnd * cmd)¶ perform DMA mapping against command’s sg lists
Parameters
struct scsi_cmnd * cmd
- scsi command
Description
Returns the number of sg lists actually used, zero if the sg lists is NULL, or -ENOMEM if the mapping failed.
-
void
scsi_dma_unmap
(struct scsi_cmnd * cmd)¶ unmap command’s sg lists mapped by scsi_dma_map
Parameters
struct scsi_cmnd * cmd
- scsi command
drivers/scsi/scsi_module.c¶
The file drivers/scsi/scsi_module.c contains legacy support for old-style host templates. It should never be used by any new driver.
drivers/scsi/scsi_proc.c¶
The functions in this file provide an interface between the PROC file system and the SCSI device drivers It is mainly used for debugging, statistics and to pass information directly to the lowlevel driver. I.E. plumbing to manage /proc/scsi/*
-
void
scsi_proc_hostdir_add
(struct scsi_host_template * sht)¶ Create directory in /proc for a scsi host
Parameters
struct scsi_host_template * sht
- owner of this directory
Description
Sets sht->proc_dir to the new directory.
-
void
scsi_proc_hostdir_rm
(struct scsi_host_template * sht)¶ remove directory in /proc for a scsi host
Parameters
struct scsi_host_template * sht
- owner of directory
-
void
scsi_proc_host_add
(struct Scsi_Host * shost)¶ Add entry for this host to appropriate /proc dir
Parameters
struct Scsi_Host * shost
- host to add
-
void
scsi_proc_host_rm
(struct Scsi_Host * shost)¶ remove this host’s entry from /proc
Parameters
struct Scsi_Host * shost
- which host
Parameters
struct device * dev
- A scsi device
void * data
struct seq_file
to output to.
Description
prints Host, Channel, Id, Lun, Vendor, Model, Rev, Type, and revision.
-
int
scsi_add_single_device
(uint host, uint channel, uint id, uint lun)¶ Respond to user request to probe for/add device
Parameters
uint host
- user-supplied decimal integer
uint channel
- user-supplied decimal integer
uint id
- user-supplied decimal integer
uint lun
- user-supplied decimal integer
Description
called by writing “scsi add-single-device” to /proc/scsi/scsi.
does scsi_host_lookup()
and either user_scan()
if that transport
type supports it, or else scsi_scan_host_selected()
Note
this seems to be aimed exclusively at SCSI parallel busses.
-
int
scsi_remove_single_device
(uint host, uint channel, uint id, uint lun)¶ Respond to user request to remove a device
Parameters
uint host
- user-supplied decimal integer
uint channel
- user-supplied decimal integer
uint id
- user-supplied decimal integer
uint lun
- user-supplied decimal integer
Description
called by writing “scsi remove-single-device” to
/proc/scsi/scsi. Does a scsi_device_lookup()
and scsi_remove_device()
-
ssize_t
proc_scsi_write
(struct file * file, const char __user * buf, size_t length, loff_t * ppos)¶ handle writes to /proc/scsi/scsi
Parameters
struct file * file
- not used
const char __user * buf
- buffer to write
size_t length
- length of buf, at most PAGE_SIZE
loff_t * ppos
- not used
Description
this provides a legacy mechanism to add or remove devices by Host, Channel, ID, and Lun. To use, “echo ‘scsi add-single-device 0 1 2 3’ > /proc/scsi/scsi” or “echo ‘scsi remove-single-device 0 1 2 3’ > /proc/scsi/scsi” with “0 1 2 3” replaced by the Host, Channel, Id, and Lun.
Note
this seems to be aimed at parallel SCSI. Most modern busses (USB, SATA, Firewire, Fibre Channel, etc) dynamically assign these values to provide a unique identifier and nothing more.
-
int
proc_scsi_open
(struct inode * inode, struct file * file)¶ glue function
Parameters
struct inode * inode
- not used
struct file * file
- passed to
single_open()
Description
Associates proc_scsi_show with this file
-
int
scsi_init_procfs
(void)¶ create scsi and scsi/scsi in procfs
Parameters
void
- no arguments
-
void
scsi_exit_procfs
(void)¶ Remove scsi/scsi and scsi from procfs
Parameters
void
- no arguments
drivers/scsi/scsi_netlink.c¶
Infrastructure to provide async events from transports to userspace via netlink, using a single NETLINK_SCSITRANSPORT protocol for all transports. See the original patch submission for more details.
Parameters
struct sk_buff * skb
- socket receive buffer
Description
- Extracts message from a receive buffer.
- Validates message header and calls appropriate transport message handler
-
void
scsi_netlink_init
(void)¶ Called by SCSI subsystem to initialize the SCSI transport netlink interface
Parameters
void
- no arguments
-
void
scsi_netlink_exit
(void)¶ Called by SCSI subsystem to disable the SCSI transport netlink interface
Parameters
void
- no arguments
drivers/scsi/scsi_scan.c¶
Scan a host to determine which (if any) devices are attached. The general scanning/probing algorithm is as follows, exceptions are made to it depending on device specific flags, compilation options, and global variable (boot or module load time) settings. A specific LUN is scanned via an INQUIRY command; if the LUN has a device attached, a scsi_device is allocated and setup for it. For every id of every channel on the given host, start by scanning LUN 0. Skip hosts that don’t respond at all to a scan of LUN 0. Otherwise, if LUN 0 has a device attached, allocate and setup a scsi_device for it. If target is SCSI-3 or up, issue a REPORT LUN, and scan all of the LUNs returned by the REPORT LUN; else, sequentially scan LUNs up until some maximum is reached, or a LUN is seen that cannot have a device attached to it.
-
int
scsi_complete_async_scans
(void)¶ Wait for asynchronous scans to complete
Parameters
void
- no arguments
Description
When this function returns, any host which started scanning before this function was called will have finished its scan. Hosts which started scanning after this function was called may or may not have finished.
-
void
scsi_unlock_floptical
(struct scsi_device * sdev, unsigned char * result)¶ unlock device via a special MODE SENSE command
Parameters
struct scsi_device * sdev
- scsi device to send command to
unsigned char * result
- area to store the result of the MODE SENSE
Description
Send a vendor specific MODE SENSE (not a MODE SELECT) command. Called for BLIST_KEY devices.
-
struct scsi_device *
scsi_alloc_sdev
(struct scsi_target * starget, u64 lun, void * hostdata)¶ allocate and setup a scsi_Device
Parameters
struct scsi_target * starget
- which target to allocate a
scsi_device
for u64 lun
- which lun
void * hostdata
- usually NULL and set by ->slave_alloc instead
Description
Allocate, initialize for io, and return a pointer to a scsi_Device. Stores the shost, channel, id, and lun in the scsi_Device, and adds scsi_Device to the appropriate list.
- Return value:
- scsi_Device pointer, or NULL on failure.
-
void
scsi_target_reap_ref_release
(struct kref * kref)¶ remove target from visibility
Parameters
struct kref * kref
- the reap_ref in the target being released
Description
Called on last put of reap_ref, which is the indication that no device under this target is visible anymore, so render the target invisible in sysfs. Note: we have to be in user context here because the target reaps should be done in places where the scsi device visibility is being removed.
-
struct scsi_target *
scsi_alloc_target
(struct device * parent, int channel, uint id)¶ allocate a new or find an existing target
Parameters
struct device * parent
- parent of the target (need not be a scsi host)
int channel
- target channel number (zero if no channels)
uint id
- target id number
Description
Return an existing target if one exists, provided it hasn’t already gone into STARGET_DEL state, otherwise allocate a new target.
The target is returned with an incremented reference, so the caller is responsible for both reaping and doing a last put
-
void
scsi_target_reap
(struct scsi_target * starget)¶ check to see if target is in use and destroy if not
Parameters
struct scsi_target * starget
- target to be checked
Description
This is used after removing a LUN or doing a last put of the target it checks atomically that nothing is using the target and removes it if so.
-
int
scsi_probe_lun
(struct scsi_device * sdev, unsigned char * inq_result, int result_len, int * bflags)¶ probe a single LUN using a SCSI INQUIRY
Parameters
struct scsi_device * sdev
- scsi_device to probe
unsigned char * inq_result
- area to store the INQUIRY result
int result_len
- len of inq_result
int * bflags
- store any bflags found here
Description
Probe the lun associated with req using a standard SCSI INQUIRY;
If the INQUIRY is successful, zero is returned and the INQUIRY data is in inq_result; the scsi_level and INQUIRY length are copied to the scsi_device any flags value is stored in *bflags.
-
int
scsi_add_lun
(struct scsi_device * sdev, unsigned char * inq_result, int * bflags, int async)¶ allocate and fully initialze a scsi_device
Parameters
struct scsi_device * sdev
- holds information to be stored in the new scsi_device
unsigned char * inq_result
- holds the result of a previous INQUIRY to the LUN
int * bflags
- black/white list flag
int async
- 1 if this device is being scanned asynchronously
Description
Initialize the scsi_device sdev. Optionally set fields based on values in *bflags.
Return
SCSI_SCAN_NO_RESPONSE: could not allocate or setup a scsi_device SCSI_SCAN_LUN_PRESENT: a new scsi_device was allocated and initialized
-
unsigned char *
scsi_inq_str
(unsigned char * buf, unsigned char * inq, unsigned first, unsigned end)¶ print INQUIRY data from min to max index, strip trailing whitespace
Parameters
unsigned char * buf
- Output buffer with at least end-first+1 bytes of space
unsigned char * inq
- Inquiry buffer (input)
unsigned first
- Offset of string into inq
unsigned end
- Index after last character in inq
-
int
scsi_probe_and_add_lun
(struct scsi_target * starget, u64 lun, int * bflagsp, struct scsi_device ** sdevp, enum scsi_scan_mode rescan, void * hostdata)¶ probe a LUN, if a LUN is found add it
Parameters
struct scsi_target * starget
- pointer to target device structure
u64 lun
- LUN of target device
int * bflagsp
- store bflags here if not NULL
struct scsi_device ** sdevp
- probe the LUN corresponding to this scsi_device
enum scsi_scan_mode rescan
- if not equal to SCSI_SCAN_INITIAL skip some code only needed on first scan
void * hostdata
- passed to
scsi_alloc_sdev()
Description
Call scsi_probe_lun, if a LUN with an attached device is found, allocate and set it up by calling scsi_add_lun.
Return
SCSI_SCAN_NO_RESPONSE: could not allocate or setup a scsi_device
- SCSI_SCAN_TARGET_PRESENT: target responded, but no device is
attached at the LUN
SCSI_SCAN_LUN_PRESENT: a new scsi_device was allocated and initialized
-
void
scsi_sequential_lun_scan
(struct scsi_target * starget, int bflags, int scsi_level, enum scsi_scan_mode rescan)¶ sequentially scan a SCSI target
Parameters
struct scsi_target * starget
- pointer to target structure to scan
int bflags
- black/white list flag for LUN 0
int scsi_level
- Which version of the standard does this device adhere to
enum scsi_scan_mode rescan
- passed to
scsi_probe_add_lun()
Description
Generally, scan from LUN 1 (LUN 0 is assumed to already have been scanned) to some maximum lun until a LUN is found with no device attached. Use the bflags to figure out any oddities.
Modifies sdevscan->lun.
-
int
scsi_report_lun_scan
(struct scsi_target * starget, int bflags, enum scsi_scan_mode rescan)¶ Scan using SCSI REPORT LUN results
Parameters
struct scsi_target * starget
- which target
int bflags
- Zero or a mix of BLIST_NOLUN, BLIST_REPORTLUN2, or BLIST_NOREPORTLUN
enum scsi_scan_mode rescan
- nonzero if we can skip code only needed on first scan
Description
Fast scanning for modern (SCSI-3) devices by sending a REPORT LUN command. Scan the resulting list of LUNs by calling scsi_probe_and_add_lun.
If BLINK_REPORTLUN2 is set, scan a target that supports more than 8 LUNs even if it’s older than SCSI-3. If BLIST_NOREPORTLUN is set, return 1 always. If BLIST_NOLUN is set, return 0 always. If starget->no_report_luns is set, return 1 always.
Return
0: scan completed (or no memory, so further scanning is futile) 1: could not scan with REPORT LUN
-
struct async_scan_data *
scsi_prep_async_scan
(struct Scsi_Host * shost)¶ prepare for an async scan
Parameters
struct Scsi_Host * shost
- the host which will be scanned
Return
a cookie to be passed to scsi_finish_async_scan()
Tells the midlayer this host is going to do an asynchronous scan. It reserves the host’s position in the scanning list and ensures that other asynchronous scans started after this one won’t affect the ordering of the discovered devices.
-
void
scsi_finish_async_scan
(struct async_scan_data * data)¶ asynchronous scan has finished
Parameters
struct async_scan_data * data
- cookie returned from earlier call to
scsi_prep_async_scan()
Description
All the devices currently attached to this host have been found. This function announces all the devices it has found to the rest of the system.
drivers/scsi/scsi_sysctl.c¶
Set up the sysctl entry: “/dev/scsi/logging_level” (DEV_SCSI_LOGGING_LEVEL) which sets/returns scsi_logging_level.
drivers/scsi/scsi_sysfs.c¶
SCSI sysfs interface routines.
-
void
scsi_remove_device
(struct scsi_device * sdev)¶ unregister a device from the scsi bus
Parameters
struct scsi_device * sdev
- scsi_device to unregister
Parameters
struct device * dev
- generic starget or parent of generic stargets to be removed
Note
This is slightly racy. It is possible that if the user requests the addition of another device then the target won’t be removed.
drivers/scsi/hosts.c¶
mid to lowlevel SCSI driver interface
-
int
scsi_host_set_state
(struct Scsi_Host * shost, enum scsi_host_state state)¶ Take the given host through the host state model.
Parameters
struct Scsi_Host * shost
- scsi host to change the state of.
enum scsi_host_state state
- state to change to.
Description
Returns zero if unsuccessful or an error if the requested transition is illegal.
-
void
scsi_remove_host
(struct Scsi_Host * shost)¶ remove a scsi host
Parameters
struct Scsi_Host * shost
- a pointer to a scsi host to remove
-
int
scsi_add_host_with_dma
(struct Scsi_Host * shost, struct device * dev, struct device * dma_dev)¶ add a scsi host with dma device
Parameters
struct Scsi_Host * shost
- scsi host pointer to add
struct device * dev
- a struct device of type scsi class
struct device * dma_dev
- dma device for the host
Note
You rarely need to worry about this unless you’re in a
virtualised host environments, so use the simpler scsi_add_host()
function instead.
- Return value:
- 0 on success / != 0 for error
-
struct Scsi_Host *
scsi_host_alloc
(struct scsi_host_template * sht, int privsize)¶ register a scsi host adapter instance.
Parameters
struct scsi_host_template * sht
- pointer to scsi host template
int privsize
- extra bytes to allocate for driver
Note
Allocate a new Scsi_Host and perform basic initialization. The host is not published to the scsi midlayer until scsi_add_host is called.
- Return value:
- Pointer to a new Scsi_Host
-
struct Scsi_Host *
scsi_host_lookup
(unsigned short hostnum)¶ get a reference to a Scsi_Host by host no
Parameters
unsigned short hostnum
- host number to locate
Description
- Return value:
A pointer to located Scsi_Host or NULL.
The caller must do a
scsi_host_put()
to drop the reference thatscsi_host_get()
took. Theput_device()
below dropped the reference fromclass_find_device()
.
-
struct Scsi_Host *
scsi_host_get
(struct Scsi_Host * shost)¶ inc a Scsi_Host ref count
Parameters
struct Scsi_Host * shost
- Pointer to Scsi_Host to inc.
-
void
scsi_host_put
(struct Scsi_Host * shost)¶ dec a Scsi_Host ref count
Parameters
struct Scsi_Host * shost
- Pointer to Scsi_Host to dec.
-
int
scsi_queue_work
(struct Scsi_Host * shost, struct work_struct * work)¶ Queue work to the Scsi_Host workqueue.
Parameters
struct Scsi_Host * shost
- Pointer to Scsi_Host.
struct work_struct * work
- Work to queue for execution.
Description
- Return value:
- 1 - work queued for execution 0 - work is already queued -EINVAL - work queue doesn’t exist
-
void
scsi_flush_work
(struct Scsi_Host * shost)¶ Flush a Scsi_Host’s workqueue.
Parameters
struct Scsi_Host * shost
- Pointer to Scsi_Host.
Transport classes¶
Transport classes are service libraries for drivers in the SCSI lower layer, which expose transport attributes in sysfs.
Fibre Channel transport¶
The file drivers/scsi/scsi_transport_fc.c defines transport attributes for Fibre Channel.
-
u32
fc_get_event_number
(void)¶ Obtain the next sequential FC event number
Parameters
void
- no arguments
Notes
We could have inlined this, but it would have required fc_event_seq to be exposed. For now, live with the subroutine call. Atomic used to avoid lock/unlock...
-
void
fc_host_post_event
(struct Scsi_Host * shost, u32 event_number, enum fc_host_event_code event_code, u32 event_data)¶ called to post an even on an fc_host.
Parameters
struct Scsi_Host * shost
- host the event occurred on
u32 event_number
- fc event number obtained from
get_fc_event_number()
enum fc_host_event_code event_code
- fc_host event being posted
u32 event_data
- 32bits of data for the event being posted
Notes
This routine assumes no locks are held on entry.
-
void
fc_host_post_vendor_event
(struct Scsi_Host * shost, u32 event_number, u32 data_len, char * data_buf, u64 vendor_id)¶ called to post a vendor unique event on an fc_host
Parameters
struct Scsi_Host * shost
- host the event occurred on
u32 event_number
- fc event number obtained from
get_fc_event_number()
u32 data_len
- amount, in bytes, of vendor unique data
char * data_buf
- pointer to vendor unique data
u64 vendor_id
- Vendor id
Notes
This routine assumes no locks are held on entry.
-
enum blk_eh_timer_return
fc_eh_timed_out
(struct scsi_cmnd * scmd)¶ FC Transport I/O timeout intercept handler
Parameters
struct scsi_cmnd * scmd
- The SCSI command which timed out
Description
This routine protects against error handlers getting invoked while a rport is in a blocked state, typically due to a temporarily loss of connectivity. If the error handlers are allowed to proceed, requests to abort i/o, reset the target, etc will likely fail as there is no way to communicate with the device to perform the requested function. These failures may result in the midlayer taking the device offline, requiring manual intervention to restore operation.
This routine, called whenever an i/o times out, validates the state of the underlying rport. If the rport is blocked, it returns EH_RESET_TIMER, which will continue to reschedule the timeout. Eventually, either the device will return, or devloss_tmo will fire, and when the timeout then fires, it will be handled normally. If the rport is not blocked, normal error handling continues.
Notes
This routine assumes no locks are held on entry.
-
void
fc_remove_host
(struct Scsi_Host * shost)¶ called to terminate any fc_transport-related elements for a scsi host.
Parameters
struct Scsi_Host * shost
- Which
Scsi_Host
Description
This routine is expected to be called immediately preceding the
a driver’s call to scsi_remove_host()
.
- WARNING: A driver utilizing the fc_transport, which fails to call
- this routine prior to
scsi_remove_host()
, will leave dangling objects in /sys/class/fc_remote_ports. Access to any of these objects can result in a system crash !!!
Notes
This routine assumes no locks are held on entry.
-
struct fc_rport *
fc_remote_port_add
(struct Scsi_Host * shost, int channel, struct fc_rport_identifiers * ids)¶ notify fc transport of the existence of a remote FC port.
Parameters
struct Scsi_Host * shost
- scsi host the remote port is connected to.
int channel
- Channel on shost port connected to.
struct fc_rport_identifiers * ids
- The world wide names, fc address, and FC4 port roles for the remote port.
Description
The LLDD calls this routine to notify the transport of the existence of a remote port. The LLDD provides the unique identifiers (wwpn,wwn) of the port, it’s FC address (port_id), and the FC4 roles that are active for the port.
For ports that are FCP targets (aka scsi targets), the FC transport maintains consistent target id bindings on behalf of the LLDD. A consistent target id binding is an assignment of a target id to a remote port identifier, which persists while the scsi host is attached. The remote port can disappear, then later reappear, and it’s target id assignment remains the same. This allows for shifts in FC addressing (if binding by wwpn or wwnn) with no apparent changes to the scsi subsystem which is based on scsi host number and target id values. Bindings are only valid during the attachment of the scsi host. If the host detaches, then later re-attaches, target id bindings may change.
This routine is responsible for returning a remote port structure. The routine will search the list of remote ports it maintains internally on behalf of consistent target id mappings. If found, the remote port structure will be reused. Otherwise, a new remote port structure will be allocated.
Whenever a remote port is allocated, a new fc_remote_port class device is created.
Should not be called from interrupt context.
Notes
This routine assumes no locks are held on entry.
-
void
fc_remote_port_delete
(struct fc_rport * rport)¶ notifies the fc transport that a remote port is no longer in existence.
Parameters
struct fc_rport * rport
- The remote port that no longer exists
Description
The LLDD calls this routine to notify the transport that a remote port is no longer part of the topology. Note: Although a port may no longer be part of the topology, it may persist in the remote ports displayed by the fc_host. We do this under 2 conditions:
- If the port was a scsi target, we delay its deletion by “blocking” it. This allows the port to temporarily disappear, then reappear without disrupting the SCSI device tree attached to it. During the “blocked” period the port will still exist.
- If the port was a scsi target and disappears for longer than we expect, we’ll delete the port and the tear down the SCSI device tree attached to it. However, we want to semi-persist the target id assigned to that port if it eventually does exist. The port structure will remain (although with minimal information) so that the target id bindings also remain.
If the remote port is not an FCP Target, it will be fully torn down and deallocated, including the fc_remote_port class device.
If the remote port is an FCP Target, the port will be placed in a temporary blocked state. From the LLDD’s perspective, the rport no longer exists. From the SCSI midlayer’s perspective, the SCSI target exists, but all sdevs on it are blocked from further I/O. The following is then expected.
If the remote port does not return (signaled by a LLDD call to
fc_remote_port_add()
) within the dev_loss_tmo timeout, then the scsi target is removed - killing all outstanding i/o and removing the scsi devices attached to it. The port structure will be marked Not Present and be partially cleared, leaving only enough information to recognize the remote port relative to the scsi target id binding if it later appears. The port will remain as long as there is a valid binding (e.g. until the user changes the binding type or unloads the scsi host with the binding).If the remote port returns within the dev_loss_tmo value (and matches according to the target id binding type), the port structure will be reused. If it is no longer a SCSI target, the target will be torn down. If it continues to be a SCSI target, then the target will be unblocked (allowing i/o to be resumed), and a scan will be activated to ensure that all luns are detected.
Called from normal process context only - cannot be called from interrupt.
Notes
This routine assumes no locks are held on entry.
-
void
fc_remote_port_rolechg
(struct fc_rport * rport, u32 roles)¶ notifies the fc transport that the roles on a remote may have changed.
Parameters
struct fc_rport * rport
- The remote port that changed.
u32 roles
- New roles for this port.
Description
The LLDD calls this routine to notify the transport that the roles on a remote port may have changed. The largest effect of this is if a port now becomes a FCP Target, it must be allocated a scsi target id. If the port is no longer a FCP target, any scsi target id value assigned to it will persist in case the role changes back to include FCP Target. No changes in the scsi midlayer will be invoked if the role changes (in the expectation that the role will be resumed. If it doesn’t normal error processing will take place).
Should not be called from interrupt context.
Notes
This routine assumes no locks are held on entry.
-
int
fc_block_scsi_eh
(struct scsi_cmnd * cmnd)¶ Block SCSI eh thread for blocked fc_rport
Parameters
struct scsi_cmnd * cmnd
- SCSI command that scsi_eh is trying to recover
Description
This routine can be called from a FC LLD scsi_eh callback. It blocks the scsi_eh thread until the fc_rport leaves the FC_PORTSTATE_BLOCKED, or the fast_io_fail_tmo fires. This is necessary to avoid the scsi_eh failing recovery actions for blocked rports which would lead to offlined SCSI devices.
Return
- 0 if the fc_rport left the state FC_PORTSTATE_BLOCKED.
- FAST_IO_FAIL if the fast_io_fail_tmo fired, this should be passed back to scsi_eh.
-
struct fc_vport *
fc_vport_create
(struct Scsi_Host * shost, int channel, struct fc_vport_identifiers * ids)¶ Admin App or LLDD requests creation of a vport
Parameters
struct Scsi_Host * shost
- scsi host the virtual port is connected to.
int channel
- channel on shost port connected to.
struct fc_vport_identifiers * ids
- The world wide names, FC4 port roles, etc for the virtual port.
Notes
This routine assumes no locks are held on entry.
-
int
fc_vport_terminate
(struct fc_vport * vport)¶ Admin App or LLDD requests termination of a vport
Parameters
struct fc_vport * vport
- fc_vport to be terminated
Description
Calls the LLDD vport_delete()
function, then deallocates and removes
the vport from the shost and object tree.
Notes
This routine assumes no locks are held on entry.
iSCSI transport class¶
The file drivers/scsi/scsi_transport_iscsi.c defines transport attributes for the iSCSI class, which sends SCSI packets over TCP/IP connections.
-
struct iscsi_bus_flash_session *
iscsi_create_flashnode_sess
(struct Scsi_Host * shost, int index, struct iscsi_transport * transport, int dd_size)¶ Add flashnode session entry in sysfs
Parameters
struct Scsi_Host * shost
- pointer to host data
int index
- index of flashnode to add in sysfs
struct iscsi_transport * transport
- pointer to transport data
int dd_size
- total size to allocate
Description
Adds a sysfs entry for the flashnode session attributes
Return
pointer to allocated flashnode sess on successNULL
on failure
-
struct iscsi_bus_flash_conn *
iscsi_create_flashnode_conn
(struct Scsi_Host * shost, struct iscsi_bus_flash_session * fnode_sess, struct iscsi_transport * transport, int dd_size)¶ Add flashnode conn entry in sysfs
Parameters
struct Scsi_Host * shost
- pointer to host data
struct iscsi_bus_flash_session * fnode_sess
- pointer to the parent flashnode session entry
struct iscsi_transport * transport
- pointer to transport data
int dd_size
- total size to allocate
Description
Adds a sysfs entry for the flashnode connection attributes
Return
pointer to allocated flashnode conn on successNULL
on failure
-
struct device *
iscsi_find_flashnode_sess
(struct Scsi_Host * shost, void * data, int (*fn) (struct device *dev, void *data)¶ finds flashnode session entry
Parameters
struct Scsi_Host * shost
- pointer to host data
void * data
- pointer to data containing value to use for comparison
int (*)(struct device *dev, void *data) fn
- function pointer that does actual comparison
Description
Finds the flashnode session object comparing the data passed using logic defined in passed function pointer
Return
pointer to found flashnode session device object on successNULL
on failure
-
struct device *
iscsi_find_flashnode_conn
(struct iscsi_bus_flash_session * fnode_sess)¶ finds flashnode connection entry
Parameters
struct iscsi_bus_flash_session * fnode_sess
- pointer to parent flashnode session entry
Description
Finds the flashnode connection object comparing the data passed using logic defined in passed function pointer
Return
pointer to found flashnode connection device object on successNULL
on failure
-
void
iscsi_destroy_flashnode_sess
(struct iscsi_bus_flash_session * fnode_sess)¶ destroy flashnode session entry
Parameters
struct iscsi_bus_flash_session * fnode_sess
- pointer to flashnode session entry to be destroyed
Description
Deletes the flashnode session entry and all children flashnode connection entries from sysfs
-
void
iscsi_destroy_all_flashnode
(struct Scsi_Host * shost)¶ destroy all flashnode session entries
Parameters
struct Scsi_Host * shost
- pointer to host data
Description
Destroys all the flashnode session entries and all corresponding children flashnode connection entries from sysfs
-
int
iscsi_scan_finished
(struct Scsi_Host * shost, unsigned long time)¶ helper to report when running scans are done
Parameters
struct Scsi_Host * shost
- scsi host
unsigned long time
- scan run time
Description
This function can be used by drives like qla4xxx to report to the scsi layer when the scans it kicked off at module load time are done.
-
int
iscsi_block_scsi_eh
(struct scsi_cmnd * cmd)¶ block scsi eh until session state has transistioned
Parameters
struct scsi_cmnd * cmd
- scsi cmd passed to scsi eh handler
Description
If the session is down this function will wait for the recovery timer to fire or for the session to be logged back in. If the recovery timer fires then FAST_IO_FAIL is returned. The caller should pass this error value to the scsi eh.
-
void
iscsi_unblock_session
(struct iscsi_cls_session * session)¶ set a session as logged in and start IO.
Parameters
struct iscsi_cls_session * session
- iscsi session
Description
Mark a session as ready to accept IO.
-
struct iscsi_cls_session *
iscsi_create_session
(struct Scsi_Host * shost, struct iscsi_transport * transport, int dd_size, unsigned int target_id)¶ create iscsi class session
Parameters
struct Scsi_Host * shost
- scsi host
struct iscsi_transport * transport
- iscsi transport
int dd_size
- private driver data size
unsigned int target_id
- which target
Description
This can be called from a LLD or iscsi_transport.
-
int
iscsi_destroy_session
(struct iscsi_cls_session * session)¶ destroy iscsi session
Parameters
struct iscsi_cls_session * session
- iscsi_session
Description
Can be called by a LLD or iscsi_transport. There must not be any running connections.
-
struct iscsi_cls_conn *
iscsi_create_conn
(struct iscsi_cls_session * session, int dd_size, uint32_t cid)¶ create iscsi class connection
Parameters
struct iscsi_cls_session * session
- iscsi cls session
int dd_size
- private driver data size
uint32_t cid
- connection id
Description
This can be called from a LLD or iscsi_transport. The connection is child of the session so cid must be unique for all connections on the session.
Since we do not support MCS, cid will normally be zero. In some cases for software iscsi we could be trying to preallocate a connection struct in which case there could be two connection structs and cid would be non-zero.
-
int
iscsi_destroy_conn
(struct iscsi_cls_conn * conn)¶ destroy iscsi class connection
Parameters
struct iscsi_cls_conn * conn
- iscsi cls session
Description
This can be called from a LLD or iscsi_transport.
-
int
iscsi_session_event
(struct iscsi_cls_session * session, enum iscsi_uevent_e event)¶ send session destr. completion event
Parameters
struct iscsi_cls_session * session
- iscsi class session
enum iscsi_uevent_e event
- type of event
Serial Attached SCSI (SAS) transport class¶
The file drivers/scsi/scsi_transport_sas.c defines transport attributes for Serial Attached SCSI, a variant of SATA aimed at large high-end systems.
The SAS transport class contains common code to deal with SAS HBAs, an aproximated representation of SAS topologies in the driver model, and various sysfs attributes to expose these topologies and management interfaces to userspace.
In addition to the basic SCSI core objects this transport class introduces two additional intermediate objects: The SAS PHY as represented by struct sas_phy defines an “outgoing” PHY on a SAS HBA or Expander, and the SAS remote PHY represented by struct sas_rphy defines an “incoming” PHY on a SAS Expander or end device. Note that this is purely a software concept, the underlying hardware for a PHY and a remote PHY is the exactly the same.
There is no concept of a SAS port in this code, users can see what PHYs form a wide port based on the port_identifier attribute, which is the same for all PHYs in a port.
Parameters
struct device * dev
- device belonging to the sas object
Description
Removes all SAS PHYs and remote PHYs for a given object
-
void
sas_remove_host
(struct Scsi_Host * shost)¶ tear down a Scsi_Host’s SAS data structures
Parameters
struct Scsi_Host * shost
- Scsi Host that is torn down
Description
Removes all SAS PHYs and remote PHYs for a given Scsi_Host and remove the Scsi_Host as well.
Note
Do not call scsi_remove_host()
on the Scsi_Host any more, as it is
already removed.
-
u64
sas_get_address
(struct scsi_device * sdev)¶ return the SAS address of the device
Parameters
struct scsi_device * sdev
- scsi device
Description
Returns the SAS address of the scsi device
-
unsigned int
sas_tlr_supported
(struct scsi_device * sdev)¶ checking TLR bit in vpd 0x90
Parameters
struct scsi_device * sdev
- scsi device struct
Description
Check Transport Layer Retries are supported or not. If vpd page 0x90 is present, TRL is supported.
-
void
sas_disable_tlr
(struct scsi_device * sdev)¶ setting TLR flags
Parameters
struct scsi_device * sdev
- scsi device struct
Description
Seting tlr_enabled flag to 0.
-
void
sas_enable_tlr
(struct scsi_device * sdev)¶ setting TLR flags
Parameters
struct scsi_device * sdev
- scsi device struct
Description
Seting tlr_enabled flag 1.
-
struct sas_phy *
sas_phy_alloc
(struct device * parent, int number)¶ allocates and initialize a SAS PHY structure
Parameters
struct device * parent
- Parent device
int number
- Phy index
Description
Allocates an SAS PHY structure. It will be added in the device tree below the device specified by parent, which has to be either a Scsi_Host or sas_rphy.
Return
SAS PHY allocated orNULL
if the allocation failed.
-
int
sas_phy_add
(struct sas_phy * phy)¶ add a SAS PHY to the device hierarchy
Parameters
struct sas_phy * phy
- The PHY to be added
Description
Publishes a SAS PHY to the rest of the system.
-
void
sas_phy_free
(struct sas_phy * phy)¶ free a SAS PHY
Parameters
struct sas_phy * phy
- SAS PHY to free
Description
Frees the specified SAS PHY.
Note
This function must only be called on a PHY that has not successfully been added usingsas_phy_add()
.
-
void
sas_phy_delete
(struct sas_phy * phy)¶ remove SAS PHY
Parameters
struct sas_phy * phy
- SAS PHY to remove
Description
Removes the specified SAS PHY. If the SAS PHY has an associated remote PHY it is removed before.
Parameters
const struct device * dev
- device to check
Return
1
if the device represents a SAS PHY,0
else
-
int
sas_port_add
(struct sas_port * port)¶ add a SAS port to the device hierarchy
Parameters
struct sas_port * port
- port to be added
Description
publishes a port to the rest of the system
-
void
sas_port_free
(struct sas_port * port)¶ free a SAS PORT
Parameters
struct sas_port * port
- SAS PORT to free
Description
Frees the specified SAS PORT.
Note
This function must only be called on a PORT that has not successfully been added usingsas_port_add()
.
-
void
sas_port_delete
(struct sas_port * port)¶ remove SAS PORT
Parameters
struct sas_port * port
- SAS PORT to remove
Description
Removes the specified SAS PORT. If the SAS PORT has an associated phys, unlink them from the port as well.
Parameters
const struct device * dev
- device to check
Return
1
if the device represents a SAS Port,0
else
-
struct sas_phy *
sas_port_get_phy
(struct sas_port * port)¶ try to take a reference on a port member
Parameters
struct sas_port * port
- port to check
-
void
sas_port_add_phy
(struct sas_port * port, struct sas_phy * phy)¶ add another phy to a port to form a wide port
Parameters
struct sas_port * port
- port to add the phy to
struct sas_phy * phy
- phy to add
Description
When a port is initially created, it is empty (has no phys). All ports must have at least one phy to operated, and all wide ports must have at least two. The current code makes no difference between ports and wide ports, but the only object that can be connected to a remote device is a port, so ports must be formed on all devices with phys if they’re connected to anything.
-
void
sas_port_delete_phy
(struct sas_port * port, struct sas_phy * phy)¶ remove a phy from a port or wide port
Parameters
struct sas_port * port
- port to remove the phy from
struct sas_phy * phy
- phy to remove
Description
This operation is used for tearing down ports again. It must be done to every port or wide port before calling sas_port_delete.
-
struct sas_rphy *
sas_end_device_alloc
(struct sas_port * parent)¶ allocate an rphy for an end device
Parameters
struct sas_port * parent
- which port
Description
Allocates an SAS remote PHY structure, connected to parent.
Return
SAS PHY allocated orNULL
if the allocation failed.
-
struct sas_rphy *
sas_expander_alloc
(struct sas_port * parent, enum sas_device_type type)¶ allocate an rphy for an end device
Parameters
struct sas_port * parent
- which port
enum sas_device_type type
- SAS_EDGE_EXPANDER_DEVICE or SAS_FANOUT_EXPANDER_DEVICE
Description
Allocates an SAS remote PHY structure, connected to parent.
Return
SAS PHY allocated orNULL
if the allocation failed.
-
int
sas_rphy_add
(struct sas_rphy * rphy)¶ add a SAS remote PHY to the device hierarchy
Parameters
struct sas_rphy * rphy
- The remote PHY to be added
Description
Publishes a SAS remote PHY to the rest of the system.
-
void
sas_rphy_free
(struct sas_rphy * rphy)¶ free a SAS remote PHY
Parameters
struct sas_rphy * rphy
- SAS remote PHY to free
Description
Frees the specified SAS remote PHY.
Note
This function must only be called on a remote PHY that has not successfully been added usingsas_rphy_add()
(or has beensas_rphy_remove()
‘d)
-
void
sas_rphy_delete
(struct sas_rphy * rphy)¶ remove and free SAS remote PHY
Parameters
struct sas_rphy * rphy
- SAS remote PHY to remove and free
Description
Removes the specified SAS remote PHY and frees it.
-
void
sas_rphy_unlink
(struct sas_rphy * rphy)¶ unlink SAS remote PHY
Parameters
struct sas_rphy * rphy
- SAS remote phy to unlink from its parent port
Description
Removes port reference to an rphy
-
void
sas_rphy_remove
(struct sas_rphy * rphy)¶ remove SAS remote PHY
Parameters
struct sas_rphy * rphy
- SAS remote phy to remove
Description
Removes the specified SAS remote PHY.
-
int
scsi_is_sas_rphy
(const struct device * dev)¶ check if a struct device represents a SAS remote PHY
Parameters
const struct device * dev
- device to check
Return
1
if the device represents a SAS remote PHY,0
else
-
struct scsi_transport_template *
sas_attach_transport
(struct sas_function_template * ft)¶ instantiate SAS transport template
Parameters
struct sas_function_template * ft
- SAS transport class function template
-
void
sas_release_transport
(struct scsi_transport_template * t)¶ release SAS transport template instance
Parameters
struct scsi_transport_template * t
- transport template instance
SATA transport class¶
The SATA transport is handled by libata, which has its own book of documentation in this directory.
Parallel SCSI (SPI) transport class¶
The file drivers/scsi/scsi_transport_spi.c defines transport attributes for traditional (fast/wide/ultra) SCSI busses.
-
void
spi_schedule_dv_device
(struct scsi_device * sdev)¶ schedule domain validation to occur on the device
Parameters
struct scsi_device * sdev
- The device to validate
Description
Identical tospi_dv_device()
above, except that the DV will be scheduled to occur in a workqueue later. All memory allocations are atomic, so may be called from any context including those holding SCSI locks.
-
void
spi_display_xfer_agreement
(struct scsi_target * starget)¶ Print the current target transfer agreement
Parameters
struct scsi_target * starget
- The target for which to display the agreement
Description
Each SPI port is required to maintain a transfer agreement for each other port on the bus. This function prints a one-line summary of the current agreement; more detailed information is available in sysfs.
-
int
spi_populate_tag_msg
(unsigned char * msg, struct scsi_cmnd * cmd)¶ place a tag message in a buffer
Parameters
unsigned char * msg
- pointer to the area to place the tag
struct scsi_cmnd * cmd
- pointer to the scsi command for the tag
Notes
designed to create the correct type of tag message for the particular request. Returns the size of the tag message. May return 0 if TCQ is disabled for this device.
SCSI RDMA (SRP) transport class¶
The file drivers/scsi/scsi_transport_srp.c defines transport attributes for SCSI over Remote Direct Memory Access.
-
int
srp_tmo_valid
(int reconnect_delay, int fast_io_fail_tmo, int dev_loss_tmo)¶ check timeout combination validity
Parameters
int reconnect_delay
- Reconnect delay in seconds.
int fast_io_fail_tmo
- Fast I/O fail timeout in seconds.
int dev_loss_tmo
- Device loss timeout in seconds.
Description
The combination of the timeout parameters must be such that SCSI commands are finished in a reasonable time. Hence do not allow the fast I/O fail timeout to exceed SCSI_DEVICE_BLOCK_MAX_TIMEOUT nor allow dev_loss_tmo to exceed that limit if failing I/O fast has been disabled. Furthermore, these parameters must be such that multipath can detect failed paths timely. Hence do not allow all three parameters to be disabled simultaneously.
-
void
srp_start_tl_fail_timers
(struct srp_rport * rport)¶ start the transport layer failure timers
Parameters
struct srp_rport * rport
- SRP target port.
Description
Start the transport layer fast I/O failure and device loss timers. Do not modify a timer that was already started.
-
int
srp_reconnect_rport
(struct srp_rport * rport)¶ reconnect to an SRP target port
Parameters
struct srp_rport * rport
- SRP target port.
Description
Blocks SCSI command queueing before invoking reconnect()
such that
queuecommand()
won’t be invoked concurrently with reconnect()
from outside
the SCSI EH. This is important since a reconnect()
implementation may
reallocate resources needed by queuecommand()
.
Notes
- This function neither waits until outstanding requests have finished nor
tries to abort these. It is the responsibility of the
reconnect()
function to finish outstanding commands before reconnecting to the target port. - It is the responsibility of the caller to ensure that the resources
reallocated by the
reconnect()
function won’t be used while this function is in progress. One possible strategy is to invoke this function from the context of the SCSI EH thread only. Another possible strategy is to lock the rport mutex inside each SCSI LLD callback that can be invoked by the SCSI EH (the scsi_host_template.eh_*() functions and also the scsi_host_template.:c:func:queuecommand() function).
-
enum blk_eh_timer_return
srp_timed_out
(struct scsi_cmnd * scmd)¶ SRP transport intercept of the SCSI timeout EH
Parameters
struct scsi_cmnd * scmd
- SCSI command.
Description
If a timeout occurs while an rport is in the blocked state, ask the SCSI EH to continue waiting (BLK_EH_RESET_TIMER). Otherwise let the SCSI core handle the timeout (BLK_EH_NOT_HANDLED).
Note
This function is called from soft-IRQ context and with the request queue lock held.
-
void
srp_rport_get
(struct srp_rport * rport)¶ increment rport reference count
Parameters
struct srp_rport * rport
- SRP target port.
-
void
srp_rport_put
(struct srp_rport * rport)¶ decrement rport reference count
Parameters
struct srp_rport * rport
- SRP target port.
-
struct srp_rport *
srp_rport_add
(struct Scsi_Host * shost, struct srp_rport_identifiers * ids)¶ add a SRP remote port to the device hierarchy
Parameters
struct Scsi_Host * shost
- scsi host the remote port is connected to.
struct srp_rport_identifiers * ids
- The port id for the remote port.
Description
Publishes a port to the rest of the system.
-
void
srp_rport_del
(struct srp_rport * rport)¶ remove a SRP remote port
Parameters
struct srp_rport * rport
- SRP remote port to remove
Description
Removes the specified SRP remote port.
-
void
srp_remove_host
(struct Scsi_Host * shost)¶ tear down a Scsi_Host’s SRP data structures
Parameters
struct Scsi_Host * shost
- Scsi Host that is torn down
Description
Removes all SRP remote ports for a given Scsi_Host. Must be called just before scsi_remove_host for SRP HBAs.
-
void
srp_stop_rport_timers
(struct srp_rport * rport)¶ stop the transport layer recovery timers
Parameters
struct srp_rport * rport
- SRP remote port for which to stop the timers.
Description
Must be called after srp_remove_host()
and scsi_remove_host()
. The caller
must hold a reference on the rport (rport->dev) and on the SCSI host
(rport->dev.parent).
-
struct scsi_transport_template *
srp_attach_transport
(struct srp_function_template * ft)¶ instantiate SRP transport template
Parameters
struct srp_function_template * ft
- SRP transport class function template
-
void
srp_release_transport
(struct scsi_transport_template * t)¶ release SRP transport template instance
Parameters
struct scsi_transport_template * t
- transport template instance
SCSI lower layer¶
Host Bus Adapter transport types¶
Many modern device controllers use the SCSI command set as a protocol to communicate with their devices through many different types of physical connections.
In SCSI language a bus capable of carrying SCSI commands is called a “transport”, and a controller connecting to such a bus is called a “host bus adapter” (HBA).
Debug transport¶
The file drivers/scsi/scsi_debug.c simulates a host adapter with a variable number of disks (or disk like devices) attached, sharing a common amount of RAM. Does a lot of checking to make sure that we are not getting blocks mixed up, and panics the kernel if anything out of the ordinary is seen.
To be more realistic, the simulated devices have the transport attributes of SAS disks.
For documentation see http://sg.danny.cz/sg/sdebug26.html
todo¶
Parallel (fast/wide/ultra) SCSI, USB, SATA, SAS, Fibre Channel, FireWire, ATAPI devices, Infiniband, I20, iSCSI, Parallel ports, netlink...