ABI removed symbols¶

What:

/sys/class/rfkill/rfkill[0-9]+/claim

This file was deprecated because there no longer was a way to claim just control over a single rfkill instance. This file was scheduled to be removed in 2012, and was removed in 2016. Values: 0: Kernel handles events

What:

/sys/o2cb symlink

Defined on file o2cb

This is a symlink: /sys/o2cb to /sys/fs/o2cb. The symlink is removed when new versions of ocfs2-tools which know to look in /sys/fs/o2cb are sufficiently prevalent. Don’t code new software to look here, it should try /sys/fs/o2cb instead.

What:

devfs

Defined on file devfs

devfs has been unmaintained for a number of years, has unfixable races, contains a naming policy within the kernel that is against the LSB, and can be replaced by using udev. The files fs/devfs/*, include/linux/devfs_fs*.h were removed, along with the assorted devfs function calls throughout the kernel tree.

What:

dv1394 (a.k.a. “OHCI-DV I/O support” for FireWire)

Defined on file dv1394

/dev/dv1394/* were character device files, one for each FireWire controller and for NTSC and PAL respectively, from which DV data could be received by read() or transmitted by write(). A few ioctl()s allowed limited control. This special-purpose interface has been superseded by libraw1394 + libiec61883 which are functionally equivalent, support HDV, and transparently work on top of the newer firewire kernel drivers.

What:

ip_queue

Defined on file ip_queue

ip_queue has been replaced by nfnetlink_queue which provides more advanced queueing mechanism to user-space. The ip_queue module was already announced to become obsolete years ago.

What:

raw1394 (a.k.a. “Raw IEEE1394 I/O support” for FireWire)

Defined on file raw1394

/dev/raw1394 was a character device file that allowed low-level access to FireWire buses. Its major drawbacks were its inability to implement sensible device security policies, and its low level of abstraction that required userspace clients to duplicate much of the kernel’s ieee1394 core functionality. Replaced by /dev/fw*, i.e. the <linux/firewire-cdev.h> ABI of firewire-core.

What:

tcp_dma_copybreak sysctl

Defined on file net_dma

Formerly the lower limit, in bytes, of the size of socket reads that will be offloaded to a DMA copy engine. Removed due to coherency issues of the cpu potentially touching the buffers while dma is in flight.

What:

video1394 (a.k.a. “OHCI-1394 Video support” for FireWire)

Defined on file video1394

/dev/video1394/* were character device files, one for each FireWire controller, which were used for isochronous I/O. It was added as an alternative to raw1394’s isochronous I/O functionality which had performance issues in its first generation. Any video1394 user had to use raw1394 + libraw1394 too because video1394 did not provide asynchronous I/O for device discovery and configuration. Replaced by /dev/fw*, i.e. the <linux/firewire-cdev.h> ABI of firewire-core.