[virglrenderer-devel] [PATCH v2] virgl: Add method to query supported MSAA samples and positions

[Dave Airlie]

On 28 June 2018 at 23:08, Gert Wollny <gert.wollny at collabora.com> wrote:
> Query the number of supported samples and the sample position and
> store these to the caps.v2 structure. We support only up to 16 samples.
> This implementation requires a GL host backend.
>
> v2: - glTexImage2Dmultisample is not available on a gles 3.1 host
>       and trying to call it crashed qemu (Jakob Bornecrantz)
>       Use glTexStorage2DMultisample instead and delete texture each
>       round because the texture becomes immutable.
>     - move call to get sample positions only when caps v2 needs to be
>       filled.
>

I haven't tested this yet, but there are a couple of whitespace nits.
>
>  union virgl_caps {
> diff --git a/src/vrend_formats.c b/src/vrend_formats.c
> index 0a5dd69..cd4f86f 100644
> --- a/src/vrend_formats.c
> +++ b/src/vrend_formats.c
> @@ -468,3 +468,48 @@ bool vrend_is_canonical_format(enum pipe_format format)
>        return false;
>     }
>  }
> +
> +

^ only one line please.

> +unsigned vrend_renderer_query_multisample_caps(unsigned max_samples, struct virgl_caps_v2 *caps)
> +{
> +   GLuint tex;
> +   GLuint fbo;
> +   GLenum status;
> +
> +   uint max_samples_confirmed = 1;
> +   uint test_num_samples[4] = {2,4,8,16};
> +   int out_buf_offsets[4] = {0,1,2,4};
> +
> +   glGenFramebuffers( 1, &fbo );
> +   memset(caps->sample_locations, 0, 8 * sizeof(uint32_t));
> +
> +   for (int i = 0; i < 4 && test_num_samples[i] <= max_samples; ++i) {
> +      glGenTextures(1, &tex);
> +      glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, tex);
> +      glTexStorage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, test_num_samples[i], GL_RGBA32F, 16, 16, GL_TRUE);
> +      status = glGetError();
> +      if (status == GL_NO_ERROR) {
> +         glBindFramebuffer(GL_FRAMEBUFFER, fbo);
> +         glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D_MULTISAMPLE, tex, 0);
> +         status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
> +         if (status == GL_FRAMEBUFFER_COMPLETE) {
> +            max_samples_confirmed = test_num_samples[i];
> +
> +            for (uint k = 0; k < test_num_samples[i]; ++k) {
> +               float msp[2];
> +               uint32_t compressed;
> +               glGetMultisamplefv(GL_SAMPLE_POSITION, k, msp);
> +               debug_printf("VIRGL: sample postion [%2d/%2d] = (%f, %f)\n",
> +                            k, test_num_samples[i], msp[0], msp[1]);
> +               compressed = ((unsigned)(floor(msp[0] * 16.0f)) & 0xf) << 4;
> +               compressed |= ((unsigned)(floor(msp[1] * 16.0f)) & 0xf);
> +               caps->sample_locations[out_buf_offsets[i] + (k >> 2)] |= compressed  << (8 * (k & 3));
> +            }
> +         }
> +      }
> +      glBindFramebuffer(GL_FRAMEBUFFER, 0);
> +      glDeleteTextures(1, &tex);
> +   }
> +   glDeleteFramebuffers(1, &fbo);
> +   return max_samples_confirmed;
> +}
> diff --git a/src/vrend_renderer.c b/src/vrend_renderer.c
> index 17c10db..52f1c44 100644
> --- a/src/vrend_renderer.c
> +++ b/src/vrend_renderer.c
> @@ -7213,7 +7213,6 @@ static bool vrend_renderer_fill_caps_common(uint32_t set, UNUSED uint32_t versio
>     glGetIntegerv(GL_MAX_SAMPLES, &max);
>     caps->v1.max_samples = max;
>
> -
>     /* All of the formats are common. */

Don't remove a line here.


Dave.