[PATCH] drm: document drm_mode_get_connector

[Pekka Paalanen]

On Wed, 18 Nov 2020 10:52:12 +0000
Simon Ser <contact at emersion.fr> wrote:

> Document how to perform a forced probe, and when should user-space do it.
> 
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Pekka Paalanen <ppaalanen at gmail.com>
> ---
>  include/uapi/drm/drm_mode.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 5ad10ab2a577..09647b799f39 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -368,6 +368,19 @@ enum drm_mode_subconnector {
>  #define DRM_MODE_CONNECTOR_WRITEBACK	18
>  #define DRM_MODE_CONNECTOR_SPI		19
>  
> +/**
> + * struct drm_mode_get_connector - get connector metadata
> + *
> + * If the @count_modes field is set to zero, the kernel will perform a forced
> + * probe on the connector to refresh the connector status, modes and EDID.
> + * A forced-probe can be slow and the ioctl will block.
> + *

Hi,

as I have no prior knowledge at all about how struct
drm_mode_get_connector works, the above paragraph only confuses me.
count_modes sounds totally unrelated to probing, and what does that
even do in this struct at all, how does one use this thing. I only know
the libdrm API for this. So I can't ack this bit.

> + * User-space shouldn't need to force-probe connectors in general: the kernel
> + * will automatically take care of probing connectors that don't support
> + * hot-plug detection when appropriate. However, user-space may force-probe
> + * connectors on user request (e.g. clicking a "Scan connectors" button, or
> + * opening a UI to manage screens).

This paragraph is good and clear to me.

> + */
>  struct drm_mode_get_connector {
>  
>  	__u64 encoders_ptr;


Thanks,
pq
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