[FOR CI] drm/drm_vblank: Change EINVAL by the correct errno

* [FOR CI] drm/drm_vblank: Change EINVAL by the correct errno
@ 2018-10-17 22:44 Rodrigo Siqueira
  2018-10-17 23:06 ` ✗ Fi.CI.BAT: failure for " Patchwork
  0 siblings, 1 reply; 2+ messages in thread
From: Rodrigo Siqueira @ 2018-10-17 22:44 UTC (permalink / raw)
  To: Gustavo Padovan, Maarten Lankhorst, Sean Paul, David Airlie,
	Daniel Vetter
  Cc: dri-devel, linux-kernel, intel-gfx

For historical reason, the function drm_wait_vblank_ioctl always return
-EINVAL if something gets wrong. This scenario limits the flexibility
for the userspace make detailed verification of the problem and take
some action. In particular, the validation of “if (!dev->irq_enabled)”
in the drm_wait_vblank_ioctl is responsible for checking if the driver
support vblank or not. If the driver does not support VBlank, the
function drm_wait_vblank_ioctl returns EINVAL which does not represent
the real issue; this patch changes this behavior by return EOPNOTSUPP.
Additionally, some operations are unsupported by this function, and
returns EINVAL; this patch also changes the return value to EOPNOTSUPP
in this case. Lastly, the function drm_wait_vblank_ioctl is invoked by
libdrm, which is used by many compositors; because of this, it is
important to check if this change breaks any compositor. In this sense,
the following projects were examined:

* Drm-hwcomposer
* Kwin
* Sway
* Wlroots
* Wayland-core
* Weston
* Xorg (67 different drivers)

For each repository the verification happened in three steps:

* Update the main branch
* Look for any occurrence "drmWaitVBlank" with the command:
  git grep -n "drmWaitVBlank"
* Look in the git history of the project with the command:
  git log -SdrmWaitVBlank

Finally, none of the above projects validate the use of EINVAL which
make safe, at least for these projects, to change the return values.

Change since V2:
 Daniel Vetter and Chris Wilson
 - Replace ENOTTY by EOPNOTSUPP
 - Return EINVAL if the parameters are wrong

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
---
 drivers/gpu/drm/drm_vblank.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 98e091175921..80f5a3bb427e 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -1533,10 +1533,10 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
 	unsigned int flags, pipe, high_pipe;
 
 	if (!dev->irq_enabled)
-		return -EINVAL;
+		return -EOPNOTSUPP;
 
 	if (vblwait->request.type & _DRM_VBLANK_SIGNAL)
-		return -EINVAL;
+		return -EOPNOTSUPP;
 
 	if (vblwait->request.type &
 	    ~(_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK |
-- 
2.19.1


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