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

[Rob Clark]

On Thu, Nov 3, 2016 at 10:12 AM, Ville Syrjälä
<ville.syrjala at 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 at 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()..

BR,
-R

>>       }
>>
>>       if (r->flags & DRM_MODE_FB_MODIFIERS &&
>> --
>> 2.7.4
>
> --
> Ville Syrjälä
> Intel OTC