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 ENOTTY (Inappropriate ioctl for device). Additionally, some operations are unsupported by this function, and returns EINVAL; this patch changes the return value to EOPNOTSUPP (Operation not supported). 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. Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx> --- drivers/gpu/drm/drm_vblank.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 98e091175921..88ec6fb49afb 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 -ENOTTY; if (vblwait->request.type & _DRM_VBLANK_SIGNAL) - return -EINVAL; + return -EOPNOTSUPP; if (vblwait->request.type & ~(_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK | @@ -1545,7 +1545,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data, vblwait->request.type, (_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK | _DRM_VBLANK_HIGH_CRTC_MASK)); - return -EINVAL; + return -EOPNOTSUPP; } flags = vblwait->request.type & _DRM_VBLANK_FLAGS_MASK; -- 2.19.0
