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

[Dmitry Torokhov]

On Wed, Jan 26, 2011 at 03:29:09PM -0200, Mauro Carvalho Chehab wrote:
> Em 26-01-2011 14:51, Dmitry Torokhov escreveu:
> > On Wed, Jan 26, 2011 at 12:18:29PM -0200, Mauro Carvalho Chehab wrote:
> >> diff --git a/input.c b/input.c
> >> index d57a31e..a9bd5e8 100644
> >> --- a/input.c
> >> +++ b/input.c
> >> @@ -101,8 +101,8 @@ int device_open(int nr, int verbose)
> >>  		close(fd);
> >>  		return -1;
> >>  	}
> >> -	if (EV_VERSION != version) {
> >> -		fprintf(stderr, "protocol version mismatch (expected %d, got %d)\n",
> >> +	if (EV_VERSION > version) {
> >> +		fprintf(stderr, "protocol version mismatch (expected >= %d, got %d)\n",
> >>  			EV_VERSION, version);
> > 
> > Please do not do this. It causes check to "float" depending on the
> > version of kernel headers it was compiled against.
> > 
> > The check should be against concrete version (0x10000 in this case).
> 
> The idea here is to not prevent it to load if version is 0x10001.
> This is actually the only change that it is really needed (after applying
> your KEY_RESERVED patch to 2.6.37) for the tool to work. Reverting it causes
> the error:

You did not understand. When comparing against EV_VERSION, if you
compile on 2.6.32 you are comparing with 0x10000. If you are compiling
on 2.6.37 you are comparing with 0x10001 as EV_VERSION value changes
(not the value returned by EVIOCGVERSION, the value of the _define_
itself).

The proper check is:

#define EVDEV_MIN_VERSION 0x10000
	if (version < EVDEV_MIN_VERSION) {
		fprintf(stderr,
			"protocol version mismatch (need at least %d, got %d)\n",
			EVDEV_MIN_VERSION, version);
		...
	}

-- 
Dmitry
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