Re: [PATCH] drm: move check for min/max width/height for atomic drivers

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Nov 03, 2016 at 11:22:37AM -0400, Rob Clark wrote:
> On Thu, Nov 3, 2016 at 10:55 AM, Ville Syrjälä
> <ville.syrjala@linux.intel.com> wrote:
> > On Thu, Nov 03, 2016 at 10:14:20AM -0400, Rob Clark wrote:
> >> On Thu, Nov 3, 2016 at 10:12 AM, Ville Syrjälä
> >> <ville.syrjala@linux.intel.com> wrote:
> >> > On Wed, Nov 02, 2016 at 10:27:44AM -0400, Rob Clark wrote:
> >> >> drm-hwc + android tries to create an fb for the wallpaper layer, which
> >> >> is larger than the screen resolution, and potentially larger than
> >> >> mode_config->max_{width,height}.  But the plane src_w/src_h is within
> >> >> the max limits, so it is something the hardware can otherwise do.
> >> >>
> >> >> For atomic drivers, defer the check to drm_atomic_plane_check().
> >> >>
> >> >> Signed-off-by: Rob Clark <robdclark@gmail.com>
> >> >> ---
> >> >>  drivers/gpu/drm/drm_atomic.c | 17 +++++++++++++++++
> >> >>  drivers/gpu/drm/drm_crtc.c   | 26 +++++++++++++++++---------
> >> >>  2 files changed, 34 insertions(+), 9 deletions(-)
> >> >>
> >> >> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> >> >> index 34edd4f..fb0f07ce 100644
> >> >> --- a/drivers/gpu/drm/drm_atomic.c
> >> >> +++ b/drivers/gpu/drm/drm_atomic.c
> >> >> @@ -846,7 +846,9 @@ plane_switching_crtc(struct drm_atomic_state *state,
> >> >>  static int drm_atomic_plane_check(struct drm_plane *plane,
> >> >>               struct drm_plane_state *state)
> >> >>  {
> >> >> +     struct drm_mode_config *config = &plane->dev->mode_config;
> >> >>       unsigned int fb_width, fb_height;
> >> >> +     unsigned int min_width, max_width, min_height, max_height;
> >> >>       int ret;
> >> >>
> >> >>       /* either *both* CRTC and FB must be set, or neither */
> >> >> @@ -909,6 +911,21 @@ static int drm_atomic_plane_check(struct drm_plane *plane,
> >> >>               return -ENOSPC;
> >> >>       }
> >> >>
> >> >> +     min_width = config->min_width << 16;
> >> >> +     max_width = config->max_width << 16;
> >> >> +     min_height = config->min_height << 16;
> >> >> +     max_height = config->max_height << 16;
> >> >> +
> >> >> +     /* Make sure source dimensions are within bounds. */
> >> >> +     if (min_width > state->src_w || state->src_w > max_width ||
> >> >> +         min_height > state->src_h || state->src_h > max_height) {
> >> >> +             DRM_DEBUG_ATOMIC("Invalid source size "
> >> >> +                              "%u.%06ux%u.%06u\n",
> >> >> +                              state->src_w >> 16, ((state->src_w & 0xffff) * 15625) >> 10,
> >> >> +                              state->src_h >> 16, ((state->src_h & 0xffff) * 15625) >> 10);
> >> >> +             return -ERANGE;
> >> >> +     }
> >> >> +
> >> >>       if (plane_switching_crtc(state->state, plane, state)) {
> >> >>               DRM_DEBUG_ATOMIC("[PLANE:%d:%s] switching CRTC directly\n",
> >> >>                                plane->base.id, plane->name);
> >> >> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> >> >> index b4b973f..7294bde 100644
> >> >> --- a/drivers/gpu/drm/drm_crtc.c
> >> >> +++ b/drivers/gpu/drm/drm_crtc.c
> >> >> @@ -3369,15 +3369,23 @@ internal_framebuffer_create(struct drm_device *dev,
> >> >>               return ERR_PTR(-EINVAL);
> >> >>       }
> >> >>
> >> >> -     if ((config->min_width > r->width) || (r->width > config->max_width)) {
> >> >> -             DRM_DEBUG_KMS("bad framebuffer width %d, should be >= %d && <= %d\n",
> >> >> -                       r->width, config->min_width, config->max_width);
> >> >> -             return ERR_PTR(-EINVAL);
> >> >> -     }
> >> >> -     if ((config->min_height > r->height) || (r->height > config->max_height)) {
> >> >> -             DRM_DEBUG_KMS("bad framebuffer height %d, should be >= %d && <= %d\n",
> >> >> -                       r->height, config->min_height, config->max_height);
> >> >> -             return ERR_PTR(-EINVAL);
> >> >> +     /* for atomic drivers, we check the src dimensions in
> >> >> +      * drm_atomic_plane_check().. allow creation of a fb
> >> >> +      * that is larger than what can be scanned out, as
> >> >> +      * long as userspace doesn't try to scanout a portion
> >> >> +      * of the fb that is too large.
> >> >> +      */
> >> >> +     if (!file_priv->atomic) {
> >> >> +             if ((config->min_width > r->width) || (r->width > config->max_width)) {
> >> >> +                     DRM_DEBUG_KMS("bad framebuffer width %d, should be >= %d && <= %d\n",
> >> >> +                               r->width, config->min_width, config->max_width);
> >> >> +                     return ERR_PTR(-EINVAL);
> >> >> +             }
> >> >> +             if ((config->min_height > r->height) || (r->height > config->max_height)) {
> >> >> +                     DRM_DEBUG_KMS("bad framebuffer height %d, should be >= %d && <= %d\n",
> >> >> +                               r->height, config->min_height, config->max_height);
> >> >> +                     return ERR_PTR(-EINVAL);
> >> >> +             }
> >> >
> >> > So why not just bump max_foo in your driver?
> >> >
> >> > Removing the restriction from the core seems likely to break some
> >> > drivers as they would now have to check the fb dimensions themselves.
> >>
> >> that is why I did it only for atomic drivers, so we could rely on the
> >> checking in drm_atomic_plane_check()..
> >
> > That's not used to check the framebuffer dimensions.
> 
> but it is used to check scanout dimensions and that is usually what
> matters..  we could add a max-pitch param if needed, but the max-fb
> dimension check is mostly useless.

There's no point in letting the user create a framebuffer that can't be
scanned out at all.

-- 
Ville Syrjälä
Intel OTC
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