On Wed, Jun 26, 2019 at 4:53 AM Daniel Vetter <daniel@xxxxxxxx> wrote: > > On Wed, Jun 26, 2019 at 4:00 AM Rodrigo Siqueira > <rodrigosiqueiramelo@xxxxxxxxx> wrote: > > > > On 06/19, Daniel Vetter wrote: > > > On Wed, Jun 19, 2019 at 09:48:56AM +0200, Daniel Vetter wrote: > > > > On Tue, Jun 18, 2019 at 11:07:50PM -0300, Rodrigo Siqueira wrote: > > > > > 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 > > > > > > > > > > > > > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > > > > > > > Apologies for the confusion on the last time around. btw if someone tells > > > > you "r-b (or a-b) with these changes", then just apply the r-b/a-b tag > > > > next time around. Otherwise people will re-review the same thing over and > > > > over again. > > > > > > btw when resending patches it's good practice to add anyone who commented > > > on it (or who commented on the igt test for the same patch and other way > > > round) onto the explicit Cc: list of the patch. That way it's easier for > > > them to follow the patch evolution and do a quick r-b once they're happy. > > > > Thanks for these valuable tips. > > Do you think that is a good idea to resend this patch CC's everybody? Or > > is it ok if I just apply it? > > Hm I thought I answered that on irc ... but just today I realized that > we missed 2 ioctls. There's also drm_crtc_get_sequence_ioctl and > drm_crtc_queue_sequence_ioctl which have the same dev->irq_enabled > check and I think should be treated the same. Hi, I reexamined all the composers described in the commit message (latest versions) to check if any project use and validate the return value from drm_crtc_get_sequence_ioctl and drm_crtc_queue_sequence_ioctl. I noticed that mesa and xserver use them. FWIU replace EINVAL by EOPNOTSUPP is harmless for mesa project, however it is not the same for xserver. Take a look at line 189 and 238 of hw/xfree86/drivers/modesetting/vblank.c * https://gitlab.freedesktop.org/xorg/xserver/blob/master/hw/xfree86/drivers/modesetting/vblank.c#L238 * https://gitlab.freedesktop.org/xorg/xserver/blob/master/hw/xfree86/drivers/modesetting/vblank.c#L189 A little bit below the above lines, you can see a validation like that: if (ret != -1 || (errno != ENOTTY && errno != EINVAL)) In other words, if we change the EINVAL by EOPNOTSUPP drm_crtc_[get|queue]_sequence_ioctl we could break xserver. I noticed that Keith Packard introduced these ioctls to the kernel and also to the xserver, I will prepare a new version and CC Keith. Should I do another thing to notify xserver developers? Thanks > Can you pls resend with those addressed too? Then you can also resend > with the cc's all added. > -Daniel > > > > > > If you don't do that then much bigger chances your patch gets ignored. > > > -Daniel > > > > > > > > > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx> > > > > > --- > > > > > 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 > > > > > > > > -- > > > > Daniel Vetter > > > > Software Engineer, Intel Corporation > > > > http://blog.ffwll.ch > > > > > > -- > > > Daniel Vetter > > > Software Engineer, Intel Corporation > > > http://blog.ffwll.ch > > > > -- > > Rodrigo Siqueira > > https://siqueira.tech > > _______________________________________________ > > Intel-gfx mailing list > > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- Rodrigo Siqueira https://siqueira.tech
