Re: [igt-dev] [PATCH i-g-t 7/8] igt: fb: Fallback on KMS dumb buffer allocation for YUV buffers

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Dec 04, 2018 at 11:08:22AM +0100, Maxime Ripard wrote:
> The current YUV buffer allocation only works on the i915 driver, since
> it uses some private ioctl. However, we can to use that code on other
> drivers that implement only KMS, so if the driver is something else
> than the i915 driver, let's allocate a dumb buffer.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> ---
>  lib/igt_fb.c | 35 +++++++++++++++++++++++++++++++++--
>  1 file changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/igt_fb.c b/lib/igt_fb.c
> index d6242a6652f1..f2e6c89f3884 100644
> --- a/lib/igt_fb.c
> +++ b/lib/igt_fb.c
> @@ -501,6 +501,8 @@ static int i915_create_gem_for_fb(struct igt_fb *fb)
>  
>  static int create_yuv_bo_for_fb(struct igt_fb *fb)
>  {
> +	unsigned int virtual_height;
> +	unsigned int bpp;
>  	uint64_t size = calc_fb_size(fb);
>  	int fd = fb->fd;
>  
> @@ -511,8 +513,37 @@ static int create_yuv_bo_for_fb(struct igt_fb *fb)
>  	if (is_i915_device(fd))
>  		return i915_create_gem_for_fb(fb);
>  
> -	/* We cannot allocate any other buffer type */
> -	igt_assert(true);
> +	switch (fb->drm_format) {
> +	case DRM_FORMAT_NV12:
> +		bpp = 8;
> +		break;
> +
> +	case DRM_FORMAT_UYVY:
> +	case DRM_FORMAT_VYUY:
> +	case DRM_FORMAT_YUYV:
> +	case DRM_FORMAT_YVYU:
> +		bpp = 16;
> +		break;
> +
> +	default:
> +		igt_assert_f(false, "Unsupported YUV format\n");
> +	}
> +
> +	switch (fb->drm_format) {
> +	case DRM_FORMAT_NV12:
> +		virtual_height = fb->height * 3 / 2;
> +		break;

A bit of a hack. The main problem with this is that the kernel won't
know anything about any stride alignment limitations etc. If we do use
this hack I guess it would be more technically correct to write it as
DIV_ROUND_UP(fb->size, fb->stride[0]), or something along those lines.

Which also brings me to the other issue we have. calc_plane_stride()
and calc_plane_size() are somewhat i915 specific. We should probably
do something about that.

> +
> +	default:
> +		virtual_height = fb->height;
> +		break;
> +	}
> +
> +	fb->is_dumb = true;
> +	fb->gem_handle = kmstest_dumb_create(fd, fb->width, virtual_height,
> +					     bpp, NULL, &fb->size);
> +
> +	return fb->gem_handle;
>  }
>  
>  /* helpers to create nice-looking framebuffers */
> -- 
> 2.19.1

-- 
Ville Syrjälä
Intel
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