[PATCH] drm: document DRM_IOCTL_MODE_RMFB

[Pekka Paalanen]

On Mon, 26 Jul 2021 07:50:32 +0000
Simon Ser <contact at emersion.fr> wrote:

> Since there's no struct to attach the docs to, document the IOCTL
> definition.
> 
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Pekka Paalanen <pekka.paalanen at collabora.com>
> Cc: Leandro Ribeiro <leandro.ribeiro at collabora.com>
> ---
>  include/uapi/drm/drm.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index e1f49dd241f7..283d61d5a243 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -1050,6 +1050,16 @@ extern "C" {
>  #define DRM_IOCTL_MODE_GETPROPBLOB	DRM_IOWR(0xAC, struct drm_mode_get_blob)
>  #define DRM_IOCTL_MODE_GETFB		DRM_IOWR(0xAD, struct drm_mode_fb_cmd)
>  #define DRM_IOCTL_MODE_ADDFB		DRM_IOWR(0xAE, struct drm_mode_fb_cmd)
> +/**
> + * DRM_IOCTL_MODE_RMFB - Remove a framebuffer.
> + *
> + * This removes a framebuffer previously added via ADDFB/ADDFB2. The IOCTL
> + * argument is a framebuffer object ID.
> + *
> + * Warning: removing a framebuffer currently in-use on an enabled plane will
> + * disable that plane. If the plane is primary, the CRTC may also be disabled
> + * (depending on driver capabilities).

Hi,

I recall some discussions around having a CRTC running with only a
non-primary plane active. Maybe we should just drop the "If the plane
is primary," part to leave it more open.

I believe no-one should take advantage of RmFB turning a CRTC off. It's
just something that can happen, so userspace needs to be aware to avoid
it.

With or without that change:

Reviewed-by: Pekka Paalanen <pekka.paalanen at collabora.com>


Thanks,
pq

> + */
>  #define DRM_IOCTL_MODE_RMFB		DRM_IOWR(0xAF, unsigned int)
>  #define DRM_IOCTL_MODE_PAGE_FLIP	DRM_IOWR(0xB0, struct drm_mode_crtc_page_flip)
>  #define DRM_IOCTL_MODE_DIRTYFB		DRM_IOWR(0xB1, struct drm_mode_fb_dirty_cmd)

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