Re: [RFC] Input: define separate EVIOCGKEYCODE_V2/EVIOCSKEYCODE_V2

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Thu, Dec 09, 2010 at 11:16:47AM -0800, Dmitry Torokhov wrote:
> On Thu, Dec 09, 2010 at 08:04:36PM +0100, Henrik Rydberg wrote:
> > On 12/09/2010 10:39 AM, Dmitry Torokhov wrote:
> > 
> > > The desire to keep old names for the EVIOCGKEYCODE/EVIOCSKEYCODE while
> > > extending them to support large scancodes was a mistake. While we tried
> > > to keep ABI intact (and we succeeded in doing that, programs compiled
> > > on older kernels will work on newer ones) there is still a problem with
> > > recompiling existing software with newer kernel headers.
> > > 
> > > New kernel headers will supply updated ioctl numbers and kernel will
> > > expect that userspace will use struct input_keymap_entry to set and
> > > retrieve keymap data. But since the names of ioctls are still the same
> > > userspace will happily compile even if not adjusted to make use of the
> > > new structure and will start miraculously fail in the field.
> > > 
> > > To avoid this issue let's revert EVIOCGKEYCODE/EVIOCSKEYCODE definitions
> > > and add EVIOCGKEYCODE_V2/EVIOCSKEYCODE_V2 so that userspace can explicitly
> > > select the style of ioctls it wants to employ.
> > > 
> > > Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
> > > ---
> > 
> > 
> > Would the header change suffice in itself?
> 
> We still need to change evdev to return -EINVAL on wrong sizes but yes,
> the amount of change there could be more limited. I just thought that
> splitting it up explicitly shows the differences in handling better. If
> people prefer the previos version we could leave it, I am 50/50 between
> them.
> 

*ping*

Mauro, Jarod, do you have an opinion on this? I think we need to settle
on a solution before 2.6.37 is out.

Thanks.

-- 
Dmitry