gcc warns about the timestamp in drm_wait_vblank being possibly used without an initialization:
drivers/gpu/drm/drm_irq.c: In function 'drm_wait_vblank': drivers/gpu/drm/drm_irq.c:1755:28: warning: 'now.tv_usec' may be used uninitialized in this function [-Wmaybe-uninitialized] vblwait->reply.tval_usec = now.tv_usec; drivers/gpu/drm/drm_irq.c:1754:27: warning: 'now.tv_sec' may be used uninitialized in this function [-Wmaybe-uninitialized] vblwait->reply.tval_sec = now.tv_sec;
This can happen if drm_vblank_count_and_time() returns 0 in its error path. To sanitize the error case, I'm changing that function to return a zero timestamp when it fails.
Signed-off-by: Arnd Bergmann arnd@arndb.de Fixes: e6ae8687a87b ("drm: idiot-proof vblank") --- drivers/gpu/drm/drm_irq.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
I'm going through the maybe-unused warnings in randconfig builds, this one is apparently not a false positive, although it only happens if something else has already gone wrong.
Originally sent out on Jan 13, but I received no reply, so resending now.
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 881c5a6c180c..6f41ddfbe061 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -997,8 +997,10 @@ u32 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe, int count = DRM_TIMESTAMP_MAXRETRIES; u32 cur_vblank;
- if (WARN_ON(pipe >= dev->num_crtcs)) + if (WARN_ON(pipe >= dev->num_crtcs)) { + *vblanktime = (struct timeval) { 0 }; return 0; + }
/* * Vblank timestamps are read lockless. To ensure consistency the vblank