[PATCH] drm/doc: describe PATH format for DP MST

[Dmitry Baryshkov]

On Mon, 23 Oct 2023 at 23:37, Simon Ser <contact at emersion.fr> wrote:
>
> This is already uAPI, xserver parses it. It's useful to document
> since user-space might want to lookup the parent connector.
>
> Additionally, people (me included) have misunderstood the PATH
> property for being stable across reboots, but since a KMS object
> ID is baked in there that's not the case. So PATH shouldn't be
> used as-is in config files and such.
>
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: Pekka Paalanen <pekka.paalanen at collabora.com>
> Cc: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>

> ---
>  drivers/gpu/drm/drm_connector.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index c3725086f413..392bec1355a3 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -1198,6 +1198,11 @@ static const u32 dp_colorspaces =
>   *     drm_connector_set_path_property(), in the case of DP MST with the
>   *     path property the MST manager created. Userspace cannot change this
>   *     property.
> + *
> + *     In the case of DP MST, the property has the format
> + *     ``mst:<parent>-<ports>`` where ``<parent>`` is the KMS object ID of the
> + *     parent connector and ``<ports>`` is a hyphen-separated list of DP MST
> + *     port numbers. Note, KMS object IDs are not stable across reboots.

Nit:  maybe `... is not guaranteed to be stable...'

>   * TILE:
>   *     Connector tile group property to indicate how a set of DRM connector
>   *     compose together into one logical screen. This is used by both high-res
> --
> 2.42.0
>
>


-- 
With best wishes
Dmitry