sysfs change of input/event devices in 2.6.23rc breaks udev

From: Anssi Hannula
Date: Sat Sep 08 2007 - 13:08:21 EST


Hi!

There seem to be changes in sysfs input structure between 2.6.22 and 2.6.23-rc5 which cause some breakage.

With 2.6.22:

# LC_ALL=C ls -l /sys/class/input/input4
total 0
drwxr-xr-x 2 root root 0 Sep 8 12:51 capabilities/
lrwxrwxrwx 1 root root 0 Sep 8 19:48 device -> ../../../devices/platform/pcspkr/
drwxr-xr-x 2 root root 0 Sep 8 12:51 event4/
drwxr-xr-x 2 root root 0 Sep 8 12:51 id/
-r--r--r-- 1 root root 4096 Sep 8 19:48 modalias
-r--r--r-- 1 root root 4096 Sep 8 19:48 name
-r--r--r-- 1 root root 4096 Sep 8 19:48 phys
lrwxrwxrwx 1 root root 0 Sep 8 19:48 subsystem -> ../../../class/input/
--w------- 1 root root 4096 Sep 8 19:48 uevent
-r--r--r-- 1 root root 4096 Sep 8 19:48 uniq

# ls -l /sys/class/input/event4
lrwxrwxrwx 1 root root 0 Sep 8 19:48 /sys/class/input/event4 -> ../../class/input/input4/event4/
# ls -l /sys/class/input/event4/
total 0
-r--r--r-- 1 root root 4096 Sep 8 19:58 dev
lrwxrwxrwx 1 root root 0 Sep 8 19:58 device -> ../../../../devices/platform/pcspkr/
lrwxrwxrwx 1 root root 0 Sep 8 19:58 subsystem -> ../../../../class/input/
--w------- 1 root root 4096 Sep 8 19:58 uevent

With 2.6.23-rc5:

# ls -l /sys/class/input/input5
total 0
drwxr-xr-x 2 root root 0 Sep 8 19:47 capabilities/
lrwxrwxrwx 1 root root 0 Sep 8 19:03 device -> ../../../devices/platform/pcspkr/
drwxr-xr-x 2 root root 0 Sep 8 19:47 id/
lrwxrwxrwx 1 root root 0 Sep 8 19:47 input:event5 -> ../../../class/input/event5/
-r--r--r-- 1 root root 4096 Sep 8 19:03 modalias
-r--r--r-- 1 root root 4096 Sep 8 19:03 name
-r--r--r-- 1 root root 4096 Sep 8 19:47 phys
drwxr-xr-x 2 root root 0 Sep 8 19:47 power/
lrwxrwxrwx 1 root root 0 Sep 8 19:03 subsystem -> ../../../class/input/
-rw-r--r-- 1 root root 4096 Sep 8 19:03 uevent
-r--r--r-- 1 root root 4096 Sep 8 19:47 uniq

# ls -l /sys/class/input/event5
total 0
-r--r--r-- 1 root root 4096 Sep 8 19:03 dev
lrwxrwxrwx 1 root root 0 Sep 8 19:03 device -> ../../../class/input/input5/
drwxr-xr-x 2 root root 0 Sep 8 19:48 power/
lrwxrwxrwx 1 root root 0 Sep 8 19:03 subsystem -> ../../../class/input/
-rw-r--r-- 1 root root 4096 Sep 8 19:03 uevent

There are a few changes.

There is no longer:
/sys/class/input/eventX => /sys/class/input/inputX/eventX
instead there is:
/sys/class/inputX/input:eventX => /sys/class/input/eventX
Notice the added "input:". I don't know if any software depends on this, though.

However, the change that broke id_path of udev is that /sys/class/input/event5/device is now a symlink to the inputX directory instead of being the same as the device symlink in inputX directory, i.e. to ../../../devices/platform/pcspkr in this case.

Udev id_path uses that directory to construct the ID_PATH variable. Should the sysfs structure be reverted or should udev be adapted to handle traversing /device symlink twice? I think the former, as there should be considerably more time to adapt udev for coming changes in sysfs.

--
Anssi Hannula
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