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Date: Tue, 18 Jun 2019 23:07:50 -0300 From: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com> To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <maxime.ripard@...tlin.com>, Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch> Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org, intel-gfx@...ts.freedesktop.org Subject: [PATCH V4] drm/drm_vblank: Change EINVAL by the correct errno 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 V3: - Return EINVAL for _DRM_VBLANK_SIGNAL (Daniel) 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@...il.com> --- drivers/gpu/drm/drm_vblank.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 603ab105125d..bed233361614 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1582,7 +1582,7 @@ 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; -- 2.21.0
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