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

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

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.

>  	}
>  
>  	if (r->flags & DRM_MODE_FB_MODIFIERS &&
> -- 
> 2.7.4

-- 
Ville Syrjälä
Intel OTC
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