[Mesa-dev] [PATCH] i965: Fail to blit rather than assert on invalid pitch requirements.

[Kenneth Graunke]

On 12/26/2012 08:32 AM, Paul Berry wrote:
> On 25 December 2012 20:55, Kenneth Graunke <kenneth at whitecape.org
> <mailto:kenneth at whitecape.org>> wrote:
>
>     Dungeon Defenders hits TexImage()'s try_pbo_upload() path where
>     image->Width == 2, which doesn't meet intelEmitCopyBlit's requirement
>     that the pitch needs to be a multiple of 4.
>
>     Since intelEmitCopyBlit can already fail for a myriad of other reasons,
>     and it's not clear that other callers are immune to this failure mode,
>     simply make it return false rather than assert.
>
>     Fixes Dungeon Defenders on i965/Ivybridge.  Now playable (aside from
>     having to work around the EXT_bindable_uniform issue).
>
>     NOTE: This is probably a candidate for the 9.0 branch.
>     ---
>       src/mesa/drivers/dri/intel/intel_blit.c | 4 ++--
>       1 file changed, 2 insertions(+), 2 deletions(-)
>
>     diff --git a/src/mesa/drivers/dri/intel/intel_blit.c
>     b/src/mesa/drivers/dri/intel/intel_blit.c
>     index 521e6eb..867d7b3 100644
>     --- a/src/mesa/drivers/dri/intel/intel_blit.c
>     +++ b/src/mesa/drivers/dri/intel/intel_blit.c
>     @@ -150,8 +150,8 @@ intelEmitCopyBlit(struct intel_context *intel,
>          /* Blit pitch must be dword-aligned.  Otherwise, the hardware
>     appears to drop
>           * the low bits.
>           */
>     -   assert(src_pitch % 4 == 0);
>     -   assert(dst_pitch % 4 == 0);
>     +   if (src_pitch % 4 != 0 || dst_pitch % 4 != 0)
>     +      return false;
>
>          /* For big formats (such as floating point), do the copy using
>     32bpp and
>           * multiply the coordinates.
>     --
>     1.8.0.2
>
>
> Looks reasonable to me.
>
> Reviewed-by: Paul Berry <stereotype441 at gmail.com
> <mailto:stereotype441 at gmail.com>>
>
> As a follow-up, we should probably check all of the code paths that lead
> into this function to make sure they invoke the proper fallback logic if
> there is a return value of false.  I think that _mesa_ReadnPixelsARB,
> for example, will just fail to copy any data.

They don't, which is bothersome...I'm not sure they check the 
preconditions nor the return value.