[igt-dev] [PATCH i-g-t] lib/igt_kms: Fix igt_display_drop_events() to work as intended

[Maarten Lankhorst]

Op 15-02-18 om 13:03 schreef Chris Wilson:
> Quoting Maarten Lankhorst (2018-02-15 11:49:17)
>> Short reads don't work, you either read the whole event or nothing
>> at all, so follow the recommendations in the documentation and
>> allocate a buffer of 4096 bytes for the event, if we capture
>> multiple events read them all.
>>
>> Cc: Jari Tahvanainen <jari.tahvanainen at intel.com>
>> Reported-by: Jari Tahvanainen <jari.tahvanainen at intel.com>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104538
>> ---
>>  lib/igt_kms.c | 20 ++++++++++++--------
>>  1 file changed, 12 insertions(+), 8 deletions(-)
>>
>> diff --git a/lib/igt_kms.c b/lib/igt_kms.c
>> index 11f23fcaaa81..5a5df61c5856 100644
>> --- a/lib/igt_kms.c
>> +++ b/lib/igt_kms.c
>> @@ -3228,14 +3228,18 @@ int igt_display_drop_events(igt_display_t *display)
>>         };
>>  
>>         while (poll(&pfd, 1, 0) > 0) {
>> -               struct drm_event ev;
>> -               char buf[128];
>> -
>> -               read(display->drm_fd, &ev, sizeof(ev));
>> -               igt_info("Dropping event type %u length %u\n", ev.type, ev.length);
>> -               igt_assert(ev.length <= sizeof(buf));
>> -               read(display->drm_fd, buf, ev.length);
> Fwiw ^ that was the bug.
>
>> -               ret++;
>> +               char buf[4096];
>> +               ssize_t retval;
>> +               struct drm_event *ev = (struct drm_event *)buf;
>> +
>> +               retval = read(display->drm_fd, &buf, sizeof(buf));
>> +               igt_assert_lt(0, retval);
>> +
>> +               for (int i = 0; i < retval; i += ev->length, ev = (struct drm_event *)&buf[i]) {
> struct drm_event *ev = (struct drm_event *)(buf +i);
>
> gets rid of the other two struct drm_event ev assignments
>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> -Chris

Pushed with that change, thanks.