[Mesa-dev] [PATCH 05/14] meta: Abort meta pbo path if readpixels need signed-unsigned conversion

[Anuj Phogat]

On Tue, Jul 21, 2015 at 1:36 AM, Iago Toral <itoral at igalia.com> wrote:
> On Tue, 2015-07-21 at 08:13 +0200, Iago Toral wrote:
>> On Mon, 2015-07-20 at 10:56 -0700, Anuj Phogat wrote:
>> > On Mon, Jul 20, 2015 at 5:10 AM, Iago Toral <itoral at igalia.com> wrote:
>> > > On Fri, 2015-06-19 at 13:40 -0700, Anuj Phogat wrote:
>> > >> On Tue, Jun 16, 2015 at 9:21 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
>> > >> >
>> > >> > On Jun 16, 2015 11:15, "Anuj Phogat" <anuj.phogat at gmail.com> wrote:
>> > >> >>
>> > >> >> Without this patch, piglit test fbo_integer_readpixels_sint_uint fails,
>> > >> >> when
>> > >> >> forced to use the meta pbo path.
>> > >> >>
>> > >> >> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
>> > >> >> Cc: <mesa-stable at lists.freedesktop.org>
>> > >> >> ---
>> > >> >>  src/mesa/drivers/common/meta_tex_subimage.c | 3 +++
>> > >> >>  1 file changed, 3 insertions(+)
>> > >> >>
>> > >> >> diff --git a/src/mesa/drivers/common/meta_tex_subimage.c
>> > >> >> b/src/mesa/drivers/common/meta_tex_subimage.c
>> > >> >> index 00364f8..84cbc50 100644
>> > >> >> --- a/src/mesa/drivers/common/meta_tex_subimage.c
>> > >> >> +++ b/src/mesa/drivers/common/meta_tex_subimage.c
>> > >> >> @@ -283,6 +283,9 @@ _mesa_meta_pbo_GetTexSubImage(struct gl_context *ctx,
>> > >> >> GLuint dims,
>> > >> >>
>> > >> >>        if (_mesa_need_rgb_to_luminance_conversion(rb->Format, format))
>> > >> >>           return false;
>> > >> >> +
>> > >> >> +      if (_mesa_need_signed_unsigned_int_conversion(rb->Format, format,
>> > >> >> type))
>> > >> >> +         return false;
>> > >> >
>> > >> > Hrm... This seems fishy.  Isn't glBlitFramebuffers supposed to handle format
>> > >> > conversion with integers?  If so we should probably fix it rather than just
>> > >> > skip it for the meta pbo path.
>> > >> >
>> > >> As discussed offline, here is relevant text for glBlitFrameBuffer() from
>> > >> OpenGL 4.5 spec, section 18.3.1:
>> > >> "An INVALID_OPERATION error is generated if format conversions are not
>> > >> supported, which occurs under any of the following conditions:
>> > >> -The read buffer contains fixed-point or floating-point values and any draw
>> > >>   buffer contains neither fixed-point nor floating-point values.
>> > >> -The read buffer contains unsigned integer values and any draw buffer does
>> > >>   not contain unsigned integer values.
>> > >> - The read buffer contains signed integer values and any draw buffer does
>> > >>   not contain signed integer values."
>> > >>
>> > >> I'll add a comment here explaining the reason to avoid meta path.
>> > >
>> > > Is this code going to run only for glBlitFramebuffer? I see this
>> > > function being called from code paths that implement glReadPixels and
>> > > glGetTexImage too.
>> > >
>> > _mesa_meta_pbo_GetTexSubImage() is used only for glReadPixels and
>> > glGetTexImage. I quoted the glBliFrameBuffer restriction above because
>> > the function is later using _mesa_meta_BlitFramebuffer(), which doesn't
>> > support some format conversions.
>>
>> If this function can be used to resolve ReadPixels and GetTexImage but
>> the checks you add are *specific* to BlitFramebuffer, it does not look
>> like this is the right place for them. Shouldn't you put them inside
>> _mesa_meta_BlitFramebuffer instead? Otherwise they would affect to
>> ReadPixels and GetTexImage too and I don't see the same restrictions
>> applying to ReadPixels for example.
We already have error checks in place for glBlitFrameBuffer(). Take a
look at compatible_color_datatypes() in _mesa_blit_framebuffer().

> Specifically for ReadPixels I only see this in the spec:
>
> "An INVALID_OPERATION error is generated if format is an integer format
> and the color buffer is not an integer format, or if the color buffer is
> an integer format and format is not an integer format."
>
> So, unlike BlitFramebuffer, it seems that ReadPixels is fine as long as
> both formats are integer, no matter if the types have the same sign or
> not.
Right. That's the reason this patch doesn't generate any GL error for
signed-unsigned int mismatch. It just decides not to use meta pbo path
because of  unsupported format conversions in _mesa_meta_BlitFrameBuffer(),
and fallback to using other paths.

>
> Iago
>
>>
>> > >> >>     }
>> > >> >>
>> > >> >>     /* For arrays, use a tall (height * depth) 2D texture but taking into
>> > >> >> --
>> > >> >> 1.9.3
>> > >> >>
>> > >> >> _______________________________________________
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>> > >
>> > >
>> >
>>
>>
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