linux-kernel - Re: 2.6.36/2.6.37: broken compatibility with userspace input-utils ?

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Date:	Tue, 25 Jan 2011 00:15:59 -0500
From:	Mark Lord <kernel@...savvy.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-input@...r.kernel.org
Subject: Re: 2.6.36/2.6.37: broken compatibility with userspace input-utils
 ?

On 11-01-25 12:07 AM, Mark Lord wrote:
> On 11-01-25 12:04 AM, Mark Lord wrote:
..
>> The EVIOCGKEYCODE ioctl is supposed to return KEY_RESERVED for unmapped
>> (but value) keycodes, and only return -EINVAL when the keycode itself
>> is out of range.
>>
>> That's how it worked in all kernels prior to 2.6.36,
>> and now it is broken.  It now returns -EINVAL for any unmapped keycode,
>> even though keycodes higher than that still have mappings.

Actually, what changed could be something different:
it's possible that this bug was always there,
and older kernels had a more complete default keymap
for the remote than that in 2.6.36+, thereby never
triggering the bug.  But I don't know that, and my best
efforts to-date to locate any of this in the kernel
have been futile.  Oh well.  :)

>> This is a bug, a regression, and breaks userspace.
>> I haven't identified *where* in the kernel the breakage happened,
>> though.. that code confuses me.  :)
> 
> Note that this device DOES have "flat scancode space",
> and the kernel is now incorrectly signalling an error (-EINVAL)
> in response to a perfectly valid query of a VALID (and mappable)
> keycode on the remote control
> 
> The code really is a valid button, it just doesn't have a default mapping
> set by the kernel (I can set a mapping for that code from userspace and it works).
> 
> This is a BUG.  Returning -EINVAL here is entirely wrong.

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