[PATCH 4/4] drm/dp/mst: Check peer device type before attempting EDID read

[Daniel Vetter]

On Wed, Oct 26, 2016 at 12:05:55PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Only certain types of pdts have the DDC bus registered, so check for
> that before we attempt the EDID read. Othwewise we risk playing around
> with an i2c adapter that doesn't actually exist.
> 
> Cc: stable at vger.kernel.org
> Cc: Carlos Santa <carlos.santa at intel.com>
> Cc: Kirill A. Shutemov <kirill at shutemov.name>
> Tested-by: Carlos Santa <carlos.santa at intel.com>
> Tested-by: Kirill A. Shutemov <kirill at shutemov.name>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97666
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 956babc161e5..690d1b407a90 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1162,7 +1162,9 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
>  			drm_dp_put_port(port);
>  			goto out;
>  		}
> -		if (port->port_num >= DP_MST_LOGICAL_PORT_0) {
> +		if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV ||
> +		     port->pdt == DP_PEER_DEVICE_SST_SINK) &&
> +		    port->port_num >= DP_MST_LOGICAL_PORT_0) {

Matches what's in drm_dp_port_setup_pdt. Not sure this is the most
reliable way to do this though, but I can't come up with anything better.

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

>  			port->cached_edid = drm_get_edid(port->connector, &port->aux.ddc);
>  			drm_mode_connector_set_tile_property(port->connector);
>  		}
> -- 
> 2.7.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch