On Tue, Oct 16, 2018 at 06:38:31PM +0200, Daniel Vetter wrote: > On Tue, Oct 16, 2018 at 03:36:20PM +0200, Maarten Lankhorst wrote: > > Op 15-10-18 om 19:05 schreef Rodrigo Siqueira: > > > 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 V1: > > > Daniel Vetter and Chris Wilson > > > - Replace ENOTTY by EOPNOTSUPP > > > - Return EINVAL if the parameters are wrong > > > > > > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx> > > > --- > > > 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; > > Change to -EIO? > > > > If userspace would ever print this out, it would print the following > > confusing message to userspace: > > "Operation not supported on transport endpoint" > > You're a bit late, EOPNOTSUPP is not established already in upstream for > this. And -EIO is taken already for "the gpu is dead". > > > > > > > if (vblwait->request.type & _DRM_VBLANK_SIGNAL) > > > - return -EINVAL; > > > + return -EOPNOTSUPP; > > I would keep this -EINVAL, tbh and making it part of the below if statement.. > > We discussed this, it's different: This here is an ioctl flag that's no > longer supported, the below is just an invalid request. Hence different > errno. > > I think you missed a bit with your bikeshed :-) I think I too agree with the -EINVAL here as this flag is never supported, whereas -EOPNOTSUPP seems to mean "this flag is still valid, but not supported by your current hardware/driver configuration". Also drm_invalid_op() uses -EINVAL for deprecated features as well. -- Ville Syrjälä Intel
