linux-kernel - Re: [2.6.23-rc9 regression] commit 4f01a757 broke HAL input support

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Date:	Fri, 05 Oct 2007 14:36:09 +0300
From:	Anssi Hannula <anssi.hannula@...il.com>
To:	Ben Gamari <ben@....ath.cx>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Andrey Borzenkov <arvidjaar@...l.ru>,
	Kay Sievers <kay.sievers@...y.org>, Greg KH <greg@...ah.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [2.6.23-rc9 regression] commit 4f01a757 broke HAL input support

Ben Gamari wrote:
> On Thu, 2007-10-04 at 22:40 -0400, Dmitry Torokhov wrote:
>> 4f01a757e75f2a3cab2bab89c4176498963946b9.
> 
> The change that Dmitry proposed would still require
> CONFIG_SYSFS_DEPRECATED, right?

What proposed change?
The changeset you quote is already applied.

Andrey Borzenkov wrote:
>> Actually this specific problem was introduced by 
>> 4f01a757e75f2a3cab2bab89c4176498963946b9. This commit seems to have 
>> completely disassociated eventX from corresponding inputY
>> 
>> To summarize.
>> 
>> 1. Any kernel with SYSFS_DEPRECATED unset
>> 
>> events are sent for /devices/...
>> /devices/.../eventX is direct child of /devices/.../inputY
>> HAL checks for parent of eventX, finds inputY and is happy
>> 
>> 2. SYSFS_DEPRECATED=y, pre-2.6.23 kernel
>> 
>> events are sent for /class/...
>> /class/.../eventX is direct child of /class/.../inputY
>> HAL checks for parent of eventX, finds inputY and works
>> 
>> 3. SYSFS_DEPRECATED=y, 2.6.23 before commit 
>> 4f01a757e75f2a3cab2bab89c4176498963946b9. 
>> 
>> events are sent for /class/...
>> /class/.../eventX is *not* child of /class/.../inputY
>> /class/.../eventX/device points to .../inputY
>> HAL checks for .../device link, finds inputY and works
>> 
>> 4. SYSFS_DEPRECATED=y, 2.6.23 after commit 
>> 4f01a757e75f2a3cab2bab89c4176498963946b9. 
>> 
>> /class/.../eventX is *not* child of /class/.../inputY
>> /class/.../eventX/device points to some physical device
>> HAL finds inputY neither as ../inputY nor as device link and breaks
>> 
>> But what is worse, now the only way to find which inputY corresponds to which 
>> eventX is to scan the whole /class/input, check for device link and compare. 

>> I am afraid that we have to bite the bullet and just accept that 2.6.23 breaks 
>> user space this way or that. Frankly fixing path_id seems to be the least 
>> evil.

I'd hate to see such breakage. IMO the sysfs structure of input devices 
should be made compatible with both HAL and udev, with both 
CONFIG_SYSFS_DEPRECATED and without it, as in 2.6.22 and before.

>> Is it possible to fall back to /class/input/inputX/eventY if SYSFS_DEPRECATED 
>> is set?

Hopefully.

-- 
Anssi Hannula
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