[Mesa-dev] [PATCH] st/mesa: fix mipmap generation for immutable textures with incomplete pyramids

[Marek Olšák]

On Fri, Oct 23, 2015 at 1:28 AM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> (This is an alternative to my previous patch, "mesa: clamp MaxLevel for
> immutable textures at initialization"; this patch has no opinion about
> how the spec should be interpreted.)
>
> Without the clamping by NumLevels, the state tracker would reallocate the
> texture storage (incorrect) and even fail to copy the base level image
> after reallocation, leading to the graphical glitch of
> https://bugs.freedesktop.org/show_bug.cgi?id=91993 .
>
> A piglit test has been submitted for review as well (subtest of
> arb_texture_storage-texture-storage).
> ---
>  src/mesa/state_tracker/st_gen_mipmap.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/src/mesa/state_tracker/st_gen_mipmap.c b/src/mesa/state_tracker/st_gen_mipmap.c
> index 26e1c21..3125b2a 100644
> --- a/src/mesa/state_tracker/st_gen_mipmap.c
> +++ b/src/mesa/state_tracker/st_gen_mipmap.c
> @@ -61,6 +61,8 @@ compute_num_levels(struct gl_context *ctx,
>
>     numLevels = texObj->BaseLevel + baseImage->MaxNumLevels;
>     numLevels = MIN2(numLevels, (GLuint) texObj->MaxLevel + 1);
> +   if (texObj->Immutable)
> +      numLevels = MIN2(numLevels, texObj->NumLevels);
>     assert(numLevels >= 1);
>
>     return numLevels;

Thanks for looking into this.

Cc: mesa-stable at lists.freedesktop.org
Reviewed-by: Marek Olšák <marek.olsak at amd.com>

While this may fix the bug, it's not immediately obvious that it won't
reallocate the texture. I think st_generate_mipmap should simply check
the immutable flag and skip all the reallocation code.

Marek