Hi Ville, Stefan, On Tue, Feb 21, 2017 at 12:55:01PM +0200, Ville Syrjälä wrote: > On Tue, Feb 21, 2017 at 11:00:59AM +0100, Stefan Lengfeld wrote: > > Hi Maxime, > > > > On Wed, Feb 15, 2017 at 05:19:09PM +0100, Maxime Ripard wrote: > > > From: Stefan Christ <s.chr...@phytec.de> > > > > > > > Maybe change the author here. Only the boilerplate code looks my original > > patch. The real code is your work ;-) > > > > > Implement legacy framebuffer ioctl FBIO_WAITFORVSYNC in the generic > > > framebuffer emulation driver. Legacy framebuffer users like non kms/drm > > > based OpenGL(ES)/EGL implementations may require the ioctl to > > > synchronize drawing or buffer flip for double buffering. It is tested on > > > the i.MX6. > > > > > > Code is based on > > > > > > https://github.com/Xilinx/linux-xlnx/blob/master/drivers/gpu/drm/xilinx/xilinx_drm_fb.c#L196 > > > > > > Signed-off-by: Stefan Christ <s.chr...@phytec.de> > > > Signed-off-by: Maxime Ripard <maxime.rip...@free-electrons.com> > > > --- > > > drivers/gpu/drm/drm_fb_helper.c | 63 ++++++++++++++++++++++++++++++++++- > > > include/drm/drm_fb_helper.h | 12 +++++- > > > 2 files changed, 74 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c > > > b/drivers/gpu/drm/drm_fb_helper.c > > > index c6de87abaca8..15ee9641c725 100644 > > > --- a/drivers/gpu/drm/drm_fb_helper.c > > > +++ b/drivers/gpu/drm/drm_fb_helper.c > > > @@ -1240,6 +1240,69 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, > > > struct fb_info *info) > > > EXPORT_SYMBOL(drm_fb_helper_setcmap); > > > > > > /** > > > + * drm_fb_helper_ioctl - legacy ioctl implementation > > > + * @info: fbdev registered by the helper > > > + * @cmd: ioctl command > > > + * @arg: ioctl argument > > > + * > > > + * A helper to implement the standard fbdev ioctl. Only > > > + * FBIO_WAITFORVSYNC is implemented for now. > > > + */ > > > +int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd, > > > + unsigned long arg) > > > +{ > > > + struct drm_fb_helper *fb_helper = info->par; > > > + struct drm_device *dev = fb_helper->dev; > > > + struct drm_mode_set *mode_set; > > > + struct drm_crtc *crtc; > > > + u32 karg; > > > + int ret = 0; > > > + > > > + mutex_lock(&dev->mode_config.mutex); > > > + if (!drm_fb_helper_is_bound(fb_helper)) { > > > + ret = -EBUSY; > > > + goto unlock; > > > + } > > > + > > > + switch (cmd) { > > > + case FBIO_WAITFORVSYNC: > > > + if (get_user(karg, (__u32 __user *)arg)) { > > > + ret = -EFAULT; > > > + goto unlock; > > > + } > > > + > > > + if (karg >= fb_helper->crtc_count) { > > > + ret = -EINVAL; > > > + goto unlock; > > > + } > > > > Ville Syrjälä said [1]: > > > > FBIO_WAITFORVSYNC takes the crtc as a parmeter, so I'm not sure we want > > to do this for all the crtcs. Though what that crtc means for fb is > > rather poorly defined. > > > > Don't think it takes the crtc as a parameter in 'arg'. When you look at the > > existing fb_ioctl implementations in the directory drivers/video/fbdev/, the > > argument 'arg' is either ignored or must be '0'. > > Have a look at matroxfb. > > > > > Furthmore most exiting userspace code just passes the value "0" as the > > argument. For example DirectFB: > > > > static const int zero = 0; > > [...] > > if (ioctl( dfb_fbdev->fd, FBIO_WAITFORVSYNC, &zero )) > > Again the matrox driver is different. And looks like unichrome might have > done something even more exotic with the argument. > > But I do agree that using this with the kms fbdev implementation could > be quite problematic as you can't actually know which crtcs the > fb_helper has picked.
I'm not sure what a good solution might be then. Is just waiting for always the first crtc acceptable? All the code I could find is passing 0 as an argument anyway, so that's effectively the same behaviour anyway here. And getting tearing might be a good argument in favour of moving to KMS :) Thanks Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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