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

[Mark Lord <kernel@teksavvy.com>]

On 11-01-25 12:04 AM, Mark Lord wrote:
> On 11-01-24 11:55 PM, Dmitry Torokhov wrote:
>> On Mon, Jan 24, 2011 at 11:37:06PM -0500, Mark Lord wrote:
> ..
>>> This results in (map->size==10) for 2.6.36+ (wrong),
>>> and a much larger map->size for 2.6.35 and earlier.
>>>
>>> So perhaps EVIOCGKEYCODE has changed?
>>>
>>
>> So the utility expects that all devices have flat scancode space and
>> driver might have changed so it does not recognize scancode 10 as valid
>> scancode anymore.
>>
>> The options are:
>>
>> 1. Convert to EVIOCGKEYCODE2
>> 2. Ignore errors from EVIOCGKEYCODE and go through all 65536 iterations.
> 
> or 3. Revert/fix the in-kernel regression.
> 
> 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.
> 
> 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.

Cheers