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

Dmitry Torokhov
2011-01-25T16:48:13Z

On Tue, Jan 25, 2011 at 09:42:44AM -0200, Mauro Carvalho Chehab wrote:
> Em 25-01-2011 03:31, Dmitry Torokhov escreveu:
> > On Tue, Jan 25, 2011 at 12:07:29AM -0500, Mark Lord wrote:
> >> 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).
> >>
> >
> > OK, in this case let's ping Mauro - I think he done the adjustments to
> > IR keymap hanlding.
>
> I lost part of the thread, but a quick search via the Internet showed that you're using
> the input tools to work with a Remote Controller, right? Are you using a vanilla
> kernel, or are you using the media_build backports? There are some distros that are
> using those backports also like Fedora 14.
>
> In the latter case, I found the reason why the backports were not working and I fixed
> it a couple days ago:
> http://git.linuxtv.org/media_build.git?a=commit;h=b83dc3e49d90527d8e1016d09e06f4842a6a847a
>
> The issue is simple, and it is related on how the input.c used to handle EVIOSGKEYCODE.
> Basically, before allowing you to change a key, it used to call EVIOCGKEYCODE to check
> it that key exists. However, when you're creating a new association, the key didn't
> exist, and, to be strict with input rules, EVIOCGKEYCODE should return -EINVAL.

We should be able to handle the case where scancode is valid even though
it might be unmapped yet. This is regardless of what version of
EVIOCGKEYCODE we use, 1 or 2, and whether it is sparse keymap or not.

Is it possible to validate the scancode by driver?

--
Dmitry