On Thu, 13 Jun 2019 21:43:34 +0300
Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> The PATH blob is already being parsed by userspace for MST connectors
> so the layout of the blob is now uabi. Let's document what it should
> look like.
>
> Also add a clear note saying non-MST connectors can have a PATH prop
> too.
>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Cc: Pekka Paalanen <ppaalanen@xxxxxxxxx>
> Cc: Ilia Mirkin <imirkin@xxxxxxxxxxxx>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_connector.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index e17586aaa80f..ce3926e9ad11 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -899,7 +899,16 @@ static const struct drm_prop_enum_list hdmi_colorspaces[] = {
> * connected. Used by DP MST. This should be set by calling
> * drm_connector_set_path_property(), in the case of DP MST with the
> * path property the MST manager created. Userspace cannot change this
> - * property.
> + * property. The value must be an ASCII string.
> + *
> + * For DP MST connectors the path string follows the pattern
> + * "mst:<base connector ID>[-<mst port>]...", where the base connector ID
> + * identifies the DP connector on the source device, and the mst ports
> + * are the port numbers in the DP MST topology.
Hi,
what exactly is the connector ID as already used here for MST? Is it
not persistent?
I assume the MST port numbers are persistent as long as the physical
topology does not change.
> + *
> + * For non-DP MST connectors the format is freeform, as long as it
> + * uniquely identifies the physical path, remains stable across
> + * kernel releases, and does not start with "mst:".
Maybe the requirements for "persistent name" should be clarified more:
- remains stable across kernel releases
- is immune to driver loading/initialisation order changes
- is immune to adding or removing other hardware (e.g. graphics cards)
Maybe also some explicit words about what to do with dynamic non-MST
connectors?
Thanks,
pq
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