Re: [PATCH] drm/display/dp: Rename bit 4 of DPCD TEST_REQUEST to match DP2.1 spec

["Almahallawy, Khaled" <khaled.almahallawy@intel.com>]

On Wed, 2025-10-29 at 10:42 +0100, Konrad Dybcio wrote:
> On 10/28/25 11:28 PM, Khaled Almahallawy wrote:
> > The DP_TEST_LINK_FAUX_PATTERN field was deprecated in the DP 1.3
> > spec.
> > Update its name to align with the DP 2.1 definition and reflect its
> > actual use in the code. No functional changes.
> > 
> > Cc: Jani Nikula <jani.nikula@intel.com>
> > Cc: Rob Clark <robin.clark@oss.qualcomm.com>
> > Cc: Dmitry Baryshkov <lumag@kernel.org>
> > Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
> > Cc: Sean Paul <sean@poorly.run>
> > Signed-off-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
> > ---
> >  drivers/gpu/drm/msm/dp/dp_link.c | 2 +-
> >  include/drm/display/drm_dp.h     | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/msm/dp/dp_link.c
> > b/drivers/gpu/drm/msm/dp/dp_link.c
> > index 66e1bbd80db3..5d465cf4dbc2 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_link.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_link.c
> > @@ -665,7 +665,7 @@ static int msm_dp_link_parse_request(struct
> > msm_dp_link_private *link)
> >  		return rlen;
> >  	}
> >  
> > -	if (!data || (data == DP_TEST_LINK_FAUX_PATTERN)) {
> > +	if (!data || (data ==
> > DP_TEST_PHY_TEST_CHANNEL_CODING_TYPE)) {
> >  		drm_dbg_dp(link->drm_dev, "link 0x%x not
> > supported\n", data);
> >  		goto end;
> >  	}
> > diff --git a/include/drm/display/drm_dp.h
> > b/include/drm/display/drm_dp.h
> > index e4eebabab975..610b8cbf1125 100644
> > --- a/include/drm/display/drm_dp.h
> > +++ b/include/drm/display/drm_dp.h
> > @@ -849,7 +849,7 @@
> >  # define DP_TEST_LINK_VIDEO_PATTERN	    (1 << 1)
> >  # define DP_TEST_LINK_EDID_READ		    (1 << 2)
> >  # define DP_TEST_LINK_PHY_TEST_PATTERN	    (1 << 3) /* DPCD >=
> > 1.1 */
> > -# define DP_TEST_LINK_FAUX_PATTERN	    (1 << 4) /* DPCD >=
> > 1.2 */
> > +# define DP_TEST_PHY_TEST_CHANNEL_CODING_TYPE	    (1 << 4)
> 
> I think it'd be useful to keep a comment of what it was before the
> deprecation and rename

Given that msm is currently the only driver that reads this bit and
correctly interprets it when handling automated test requests to
determine 128b/132b support—and following the style used throughout
this file, since I don’t see other examples referencing deprecated
names in comments

what do you think about using something like this instead?

#define DP_TEST_PHY_TEST_CHANNEL_CODING_TYPE  (1 << 4) /* DP 2.1 */

Thank You
Khaled
> 
> Konrad