[Mesa-dev] [PATCH] meta: Compute correct buffer size with SkipRows/SkipPixels

[Chris Wilson]

On Mon, Aug 31, 2015 at 10:29:51PM -0700, Jason Ekstrand wrote:
>    On Aug 31, 2015 6:48 AM, "Chris Wilson" <[1]chris at chris-wilson.co.uk>
>    wrote:
>    >
>    > From: Jason Ekstrand <[2]jason.ekstrand at intel.com>
>    >
>    > If the user is specifying a subregion of a buffer using SKIP_ROWS and
>    > SKIP_PIXELS, we must compute the buffer size carefully as the end of the
>    > last row may be much shorter than stride*image_height*depth. The current
>    > code tries to memcpy from beyond the end of the user data, for example
>    > causing:

>    > Fixes: 7f396189f073d626c5f7a2c232dac92b65f5a23f
> 
>    How can this fix a SHA? What repo is this SHA in?

I suppose it is an actual regression from 

commit 7f396189f073d626c5f7a2c232dac92b65f5a23f
Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Mon Jan 5 18:17:04 2015 -0800

    meta: Add a BlitFramebuffers-based implementation of TexSubImage

>    >        if (is_pixel_pack)
>    > -         _mesa_BufferData(pbo_target, row_stride * height, NULL,
>    > +         _mesa_BufferData(pbo_target,
>    > +                          last_pixel - first_pixel,
>    > +                          NULL,
> 
>    I'm trying to decide if the null here is correct... It's certainly the
>    same as what we had before but I have a nagging feeling that this should
>    be (void *)first_pixel.

It should be NULL, but the code doesn't work for the GetTexSubImage
case as it does a GPU copy into the buffer object that it creates but
then never reads it back from the buffer object into the client memory.
Fortunately the non-pbo path is not used for GetTexImage.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre