Re: [PATCH] drm/virtio: add overlay plane format support

[Dmitry Osipenko]

24.09.2026 17:22, Baorui.Liu пишет:
> From: Sophia Gong <lili.gong@xxxxxxx>
> 
> Advertise additional pixel formats for virtio-gpu overlay planes so a
> userspace compositor can use KMS overlay composition instead of
> falling back to GPU composition.
> 
> Handle DRM_PLANE_TYPE_OVERLAY in virtio_gpu_plane_init() with a
> dedicated format list, and reuse the primary plane update path for
> overlay scanout.
> 
> Signed-off-by: Sophia Gong <lili.gong@xxxxxxx>
> Signed-off-by: Baorui.Liu <baorliu@xxxxxxx>
> ---
>  drivers/gpu/drm/virtio/virtgpu_plane.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
> index 29e4b458ae57..23ca880692f1 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_plane.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
> @@ -41,6 +41,21 @@ static const uint32_t virtio_gpu_cursor_formats[] = {
>  	DRM_FORMAT_HOST_ARGB8888,
>  };
>  
> +static const uint32_t virtio_gpu_overlay_formats[] = {
> +	DRM_FORMAT_XRGB8888,
> +	DRM_FORMAT_ARGB8888,
> +	DRM_FORMAT_BGRX8888,
> +	DRM_FORMAT_BGRA8888,
> +	DRM_FORMAT_RGBX8888,
> +	DRM_FORMAT_RGBA8888,
> +	DRM_FORMAT_XBGR8888,
> +	DRM_FORMAT_ABGR8888,
> +	DRM_FORMAT_XRGB2101010,
> +	DRM_FORMAT_BGRX1010102,
> +	DRM_FORMAT_NV12,
> +	DRM_FORMAT_P010,
> +};
> +
>  uint32_t virtio_gpu_translate_format(uint32_t drm_fourcc)
>  {
>  	uint32_t format;
> @@ -572,6 +587,13 @@ static const struct drm_plane_helper_funcs virtio_gpu_cursor_helper_funcs = {
>  	.atomic_update		= virtio_gpu_cursor_plane_update,
>  };
>  
> +static const struct drm_plane_helper_funcs virtio_gpu_overlay_helper_funcs = {
> +	.prepare_fb		= virtio_gpu_plane_prepare_fb,
> +	.cleanup_fb		= virtio_gpu_plane_cleanup_fb,
> +	.atomic_check		= virtio_gpu_plane_atomic_check,
> +	.atomic_update		= virtio_gpu_primary_plane_update,
> +};
> +
>  struct drm_plane *virtio_gpu_plane_init(struct virtio_gpu_device *vgdev,
>  					enum drm_plane_type type,
>  					int index)
> @@ -586,6 +608,10 @@ struct drm_plane *virtio_gpu_plane_init(struct virtio_gpu_device *vgdev,
>  		formats = virtio_gpu_cursor_formats;
>  		nformats = ARRAY_SIZE(virtio_gpu_cursor_formats);
>  		funcs = &virtio_gpu_cursor_helper_funcs;
> +	} else if (type == DRM_PLANE_TYPE_OVERLAY) {
> +		formats = virtio_gpu_overlay_formats;
> +		nformats = ARRAY_SIZE(virtio_gpu_overlay_formats);
> +		funcs = &virtio_gpu_overlay_helper_funcs;
>  	} else {
>  		formats = virtio_gpu_formats;
>  		nformats = ARRAY_SIZE(virtio_gpu_formats);

This won't work on its own without actually creating overlay planes and
having host supporting overlays based on virtio-gpu specification
defining how overlays are defined in protocol and work.

Upstreaming such feature will require you to provide spec, full guest
and host implementations of overlays.

-- 
Best regards,
Dmitry