[PATCH 5/6] Allow compiling against older headers

[Dmitry Torokhov]

Hi Peter,

On Thu, Sep 28, 2017 at 2:05 PM, Peter Hutterer
<peter.hutterer at who-t.net> wrote:
> On Wed, Sep 27, 2017 at 10:58:30AM -0700, Dmitry Torokhov wrote:
>> Instead of requiring to compile against the newest kernel headers or
>> lose newer certain event definitions, let's check for the presence of
>> "official" defines and add missing ones ourselves (they form ABI so
>> there is no risk of them changing and getting out of sync). This allows
>> us to produce fully-functional version of evtest even if kernel headers
>> on the build system are slightly older.
>>
>> Signed-off-by: Dmitry Torokhov <dtor at chromium.org>
>
> tbh, I'm not a big fan of this patch. The main reason I'm keeping evtest
> alive is because it's a single file and can still be compiled with a simple
> 'gcc evtest.c' without having to worry about automake, dependencies, etc.
> Once that advantage goes away evtest is a less-featureful cousin to
> evemu-record. And that has the advantage of being replayable.
>
> That aside, Martin's suggestion of just adding linux/input(-event-codes).h
> would be a better choice here, that should keep the `gcc evtest.c` option
> alive.

I must say that I am terribly confused as to how my patch breaks
"naked" gcc compilation and why Martin's suggestion would be any
different in this regard:

dtor at dtor-ws:~ $ git clone evtest evtest-tmp
Cloning into 'evtest-tmp'...
done.
dtor at dtor-ws:~ $ cd evtest-tmp/
dtor at dtor-ws:~/evtest-tmp $ gcc -o evtest evtest.c
dtor at dtor-ws:~/evtest-tmp $ sudo ./evtest
[sudo] password for dtor:
No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0:      Power Button
/dev/input/event1:      Power Button
/dev/input/event2:      HDA Intel PCH Front Mic
/dev/input/event3:      HDA Intel PCH Rear Mic
/dev/input/event4:      HDA Intel PCH Line
/dev/input/event5:      HDA Intel PCH Line Out
/dev/input/event6:      HDA Intel PCH Front Headphone
/dev/input/event7:      HP WMI hotkeys
/dev/input/event8:      HDA NVidia HDMI/DP,pcm=3
/dev/input/event9:      HDA NVidia HDMI/DP,pcm=7
/dev/input/event10:     HDA NVidia HDMI/DP,pcm=8
Select the device event number [0-10]:

Thanks,
Dmitry