Re: [PATCH] drm/i915: Use pixel size for computing linear offsets into a sprite

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Dec 19, 2012 at 12:14:22PM +0000, Chris Wilson wrote:
> This fixes an original bug in the sprite code that miscomputed the
> source offset into a linear YUV packed framebuffer, that was magnified
> into an oops with
> 
> commit 5a35e99e8162d6820013a56ad15ea8bf937af5a6
> Author: Damien Lespiau <damien.lespiau@intel.com>
> Date:   Fri Oct 26 18:20:12 2012 +0100
> 
>     drm/i915: adjust sprite base address
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.com>
> Cc: Damien Lespiau <damien.lespiau@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_sprite.c |   10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
> index 3e05d79..fef3cfb 100644
> --- a/drivers/gpu/drm/i915/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/intel_sprite.c
> @@ -120,11 +120,10 @@ ivb_update_plane(struct drm_plane *plane, struct drm_framebuffer *fb,
>  	I915_WRITE(SPRSTRIDE(pipe), fb->pitches[0]);
>  	I915_WRITE(SPRPOS(pipe), (crtc_y << 16) | crtc_x);
>  
> -	linear_offset = y * fb->pitches[0] + x * (fb->bits_per_pixel / 8);
> +	linear_offset = y * fb->pitches[0] + x * pixel_size;

Shouldn't we round x to an even offset for packed yuv? Maybe even using
drm_format_horz_chroma_subsampling ... The idea being that a generic
client can't really know the resolution for our source offsets.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch