Date:	Sat, 08 Sep 2007 22:38:39 +0300
From:	Anssi Hannula <anssi.hannula@...il.com>
To:	Andrey Borzenkov <arvidjaar@...l.ru>
CC:	linux-kernel@...r.kernel.org, Dmitry Torokhov <dtor@...ightbb.com>,
	linux-input@...ey.karlin.mff.cuni.cz,
	linux-hotplug-devel@...ts.sourceforge.net
Subject: Re: sysfs change of input/event devices in 2.6.23rc breaks udev

Andrey Borzenkov wrote:
> Anssi Hannula wrote:
> 
>> Hi!
>>
>> There seem to be changes in sysfs input structure between 2.6.22 and
>> 2.6.23-rc5 which cause some breakage.
>>
[...]
>> 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.
>>
> 
> I am using 2.6.23-rc5 in current cooker

Same kernel here, but on an older system (MDV2007.1). I tested with a 
path_id from a recent udev as well, though, but the problem was there as 
well.

> and I did not notice any breakage; 
> could you please show example of wrong path? E.g. I have
> 
> {pts/0}% LC_ALL=C ll /dev/input/by-path
> total 0
> lrwxrwxrwx 1 root root 9 Sep  2 15:00
> platform-i8042-serio-0-event-kbd -> ../event0
> lrwxrwxrwx 1 root root 9 Sep  2 15:00
> platform-i8042-serio-1-event-mouse -> ../event1
> lrwxrwxrwx 1 root root 9 Sep  2 15:00
> platform-i8042-serio-1-mouse -> ../mouse0
> 
> and it looks pretty sane for me.

I don't have anything under /dev/input/by-path as the lookup in path_id 
fails.

> Oh, and I do not have CONFIG_SYSFS_DEPRECATED which probably explains why it
> works for me :)

Probably.

> {pts/0}% LC_ALL=C ll /sys/class/input/input2/
> total 0
> drwxr-xr-x 2 root root    0 Sep  8 22:25 capabilities/
> drwxr-xr-x 3 root root    0 Sep  8 22:22 event2/
> drwxr-xr-x 2 root root    0 Sep  8 22:25 id/
> -r--r--r-- 1 root root 4096 Sep  8 22:25 modalias
> -r--r--r-- 1 root root 4096 Sep  8 22:25 name
> -r--r--r-- 1 root root 4096 Sep  8 22:25 phys
> drwxr-xr-x 2 root root    0 Sep  8 22:25 power/
> lrwxrwxrwx 1 root root    0 Sep  8 22:25
> subsystem -> ../../../../class/input/
> -rw-r--r-- 1 root root 4096 Sep  8 22:25 uevent
> -r--r--r-- 1 root root 4096 Sep  8 22:25 uniq

What does this print as devpath for you:
$ udevinfo -q all --name=input/event0

For me on 2.6.23rc5 it prints:
P: /class/input/event0
and on 2.6.22:
P: /class/input/input0/event0

Both are detected as "old sysfs layout" by path_id, but only on 2.6.22 
is there a /device symlink pointing to the expected location.

I suspect it prints something like /devices/xyz for you, right?
That seems to be detected as "new sysfs layout" by path_id and handled 
differently.

> this implies that SYSFS_DEPRECATED may be broken w.r.t. udev; OTOH it *is*
> deprecated, is not it?

Indeed, at least regarding input subsystem, for which there was a recent 
switchover [1] from class_device.

[1] 
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=9657d75c5f0f7d0a9cb507521d3ad1436aea28c9

-- 
Anssi Hannula
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