Re: [PATCH 3/3] drm: handle override edid and firmware EDID at drm_do_get_edid() level

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Feb 16, 2017 at 12:36:45PM +0200, Jani Nikula wrote:
> Handle debugfs override edid and firmware edid at the low level to
> transparently and completely replace the real edid. Previously, we
> practically only used the modes from the override EDID, and none of the
> other data. This also prevents actual EDID reads when the EDID is to be
> overridden, but retains the DDC probe.

Hmm. Isn't that a bad thing? If someone has broken DDC on their cable or
somethign then the override EDID wouldn't be returned by drm_get_edid().

> 
> FIXME: validate override edid, deduplicate firmware edid validation.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c         | 15 +++++++++++++++
>  drivers/gpu/drm/drm_probe_helper.c | 19 +------------------
>  2 files changed, 16 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 362036360724..054e2d74eafc 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -1309,6 +1309,10 @@ static void connector_bad_edid(struct drm_connector *connector,
>   * level, drivers must make all reasonable efforts to expose it as an I2C
>   * adapter and use drm_get_edid() instead of abusing this function.
>   *
> + * The EDID may be overridden using debugfs override_edid or firmare EDID
> + * (drm_load_edid_firmware()), in this priority order. Having either of them
> + * bypasses actual EDID reads.
> + *
>   * Return: Pointer to valid EDID or NULL if we couldn't find any.
>   */
>  struct edid *drm_do_get_edid(struct drm_connector *connector,
> @@ -1318,6 +1322,17 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
>  {
>  	int i, j = 0, valid_extensions = 0;
>  	u8 *edid, *new;
> +	struct edid *override = NULL;
> +
> +	if (connector->override_edid)
> +		override = drm_edid_duplicate((const struct edid *)
> +					      connector->edid_blob_ptr->data);
> +
> +	if (!override)
> +		override = drm_load_edid_firmware(connector);
> +
> +	if (!IS_ERR_OR_NULL(override))
> +		return override;
>  
>  	if ((edid = kmalloc(EDID_LENGTH, GFP_KERNEL)) == NULL)
>  		return NULL;
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index 358957118ca9..871326cbc465 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -199,8 +199,6 @@ drm_connector_detect(struct drm_connector *connector, bool force)
>   *    drm_mode_probed_add(). New modes start their life with status as OK.
>   *    Modes are added from a single source using the following priority order.
>   *
> - *    - debugfs 'override_edid' (used for testing only)
> - *    - firmware EDID (drm_load_edid_firmware())
>   *    - &drm_connector_helper_funcs.get_modes vfunc
>   *    - if the connector status is connector_status_connected, standard
>   *      VESA DMT modes up to 1024x768 are automatically added
> @@ -305,22 +303,7 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
>  		goto prune;
>  	}
>  
> -	if (connector->override_edid) {
> -		struct edid *edid = (struct edid *) connector->edid_blob_ptr->data;
> -
> -		count = drm_add_edid_modes(connector, edid);
> -		drm_edid_to_eld(connector, edid);
> -	} else {
> -		struct edid *edid = drm_load_edid_firmware(connector);
> -		if (!IS_ERR_OR_NULL(edid)) {
> -			drm_mode_connector_update_edid_property(connector, edid);
> -			count = drm_add_edid_modes(connector, edid);
> -			drm_edid_to_eld(connector, edid);
> -			kfree(edid);
> -		}
> -		if (count == 0)
> -			count = (*connector_funcs->get_modes)(connector);
> -	}
> +	count = (*connector_funcs->get_modes)(connector);
>  
>  	if (count == 0 && connector->status == connector_status_connected)
>  		count = drm_add_modes_noedid(connector, 1024, 768);
> -- 
> 2.1.4

-- 
Ville Syrjälä
Intel OTC
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