[PATCH] drm: document that user-space should avoid parsing EDIDs

[Daniel Vetter]

On Fri, Oct 9, 2020 at 11:24 AM Simon Ser <contact at emersion.fr> wrote:
>
> User-space should avoid parsing EDIDs for metadata already exposed via
> other KMS interfaces and properties. For instance, user-space should not
> try to extract a list of modes from the EDID: the kernel might mutate
> the mode list (because of link capabilities or quirks for instance).
>
> Other metadata not exposed by KMS can be parsed by user-space. This
> includes for instance monitor identification (make/model/serial) and
> supported color-spaces.
>
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Suggested-by: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/drm_connector.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 717c4e7271b0..00e58fd2d292 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -960,6 +960,10 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
>   *     drm_connector_update_edid_property(), usually after having parsed
>   *     the EDID using drm_add_edid_modes(). Userspace cannot change this
>   *     property.
> + *
> + *     User-space should not parse the EDID to obtain information exposed via
> + *     other KMS properties. For instance, user-space should not try to parse
> + *     mode lists from the EDID.
>   * DPMS:
>   *     Legacy property for setting the power state of the connector. For atomic
>   *     drivers this is only provided for backwards compatibility with existing
> --
> 2.28.0
>
>
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch