Re: [PATCH 1/3] drm: Check CRTC compatibility in setplane

[Matt Roper <matthew.d.roper@intel.com>]

On Wed, Apr 23, 2014 at 08:03:50PM +0200, Daniel Vetter wrote:
> On Wed, Apr 23, 2014 at 10:03:59AM -0700, Matt Roper wrote:
> > The DRM core setplane code should check that the plane is usable on the
> > specified CRTC before calling into the driver.
> > 
> > Prior to this patch, a plane's possible_crtcs field was purely
> > informational for userspace and was never actually verified at the
> > kernel level (aside from the primary plane helper).
> > 
> > Cc: dri-devel@lists.freedesktop.org
> > Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> 
> Do you have a nasty igt somewhere which tries to use a plane on the wrong
> crtc? Especially useful since our i915 code and hw relies on this.
> -Daniel

Not yet; I'll add/modify a test to include that.  I'm still working on
some other i-g-t test updates for the primary plane stuff based on your
previous feedback.

Speaking of i-g-t testing, what is the expected behavior if someone
issues a pageflip ioctl while the primary plane is disabled?  I'd expect
it to return an error, but the -EBUSY currently returned by the DRM core
seems a bit confusing/misleading in my opinion.  The comments indicate
that the existing assumption is that crtc->primary->fb == NULL indicates 
a hotplug event that userspace hasn't noticed yet, although now we
clearly have other ways to hit that error, so I'm not sure EBUSY is
really the right response.


Matt

> 
> > ---
> >  drivers/gpu/drm/drm_crtc.c         | 7 +++++++
> >  drivers/gpu/drm/drm_plane_helper.c | 6 ------
> >  2 files changed, 7 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > index 461d19b..b6d6c04 100644
> > --- a/drivers/gpu/drm/drm_crtc.c
> > +++ b/drivers/gpu/drm/drm_crtc.c
> > @@ -2140,6 +2140,13 @@ int drm_mode_setplane(struct drm_device *dev, void *data,
> >  	}
> >  	crtc = obj_to_crtc(obj);
> >  
> > +	/* Check whether this plane is usable on this CRTC */
> > +	if (!(plane->possible_crtcs & drm_crtc_mask(crtc))) {
> > +		DRM_DEBUG_KMS("Invalid crtc for plane\n");
> > +		ret = -EINVAL;
> > +		goto out;
> > +	}
> > +
> >  	fb = drm_framebuffer_lookup(dev, plane_req->fb_id);
> >  	if (!fb) {
> >  		DRM_DEBUG_KMS("Unknown framebuffer ID %d\n",
> > diff --git a/drivers/gpu/drm/drm_plane_helper.c b/drivers/gpu/drm/drm_plane_helper.c
> > index b72736d..65c4a00 100644
> > --- a/drivers/gpu/drm/drm_plane_helper.c
> > +++ b/drivers/gpu/drm/drm_plane_helper.c
> > @@ -137,12 +137,6 @@ int drm_primary_helper_update(struct drm_plane *plane, struct drm_crtc *crtc,
> >  		return -EINVAL;
> >  	}
> >  
> > -	/* Primary planes are locked to their owning CRTC */
> > -	if (plane->possible_crtcs != drm_crtc_mask(crtc)) {
> > -		DRM_DEBUG_KMS("Cannot change primary plane CRTC\n");
> > -		return -EINVAL;
> > -	}
> > -
> >  	/* Disallow scaling */
> >  	src_w >>= 16;
> >  	src_h >>= 16;
> > -- 
> > 1.8.5.1
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795