Re: [RFC PATCH] drm/edid: index CEA/HDMI mode tables using the VIC

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

On Wed, Dec 02, 2015 at 01:46:40PM +0200, Jani Nikula wrote:
> On Tue, 01 Dec 2015, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> > On Tue, Dec 01, 2015 at 05:16:54PM +0200, Jani Nikula wrote:
> >> Add a dummy entry to CEA/HDMI mode tables so they can be indexed
> >> directly using the VIC, avoiding a +1/-1 dance here and there. This adds
> >> clarity to the error checking for various functions that return the VIC
> >> on success and zero on failure; we now explicitly check for 0 instead of
> >> just subtracting one from an unsigned type.
> >> 
> >> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> >> 
> >> ---
> >> 
> >> This is on top of
> >> 
> >> commit 4c6bcf44549907cb50b67f98eb13717a4adc6b33
> >> Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >> Date:   Mon Nov 16 21:05:12 2015 +0200
> >> 
> >>     drm/edid: Make the detailed timing CEA/HDMI mode fixup accept up to 5kHz clock difference
> >> 
> >> in drm-intel/topic/drm-misc
> >> ---
> >>  drivers/gpu/drm/drm_edid.c | 84 ++++++++++++++++++++++++----------------------
> >>  1 file changed, 43 insertions(+), 41 deletions(-)
> >> 
> >> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> >> index c214f1246cb4..aea09eae407e 100644
> >> --- a/drivers/gpu/drm/drm_edid.c
> >> +++ b/drivers/gpu/drm/drm_edid.c
> > <snip>
> >> @@ -2713,16 +2716,16 @@ add_alternate_cea_modes(struct drm_connector *connector, struct edid *edid)
> >>  	list_for_each_entry(mode, &connector->probed_modes, head) {
> >>  		const struct drm_display_mode *cea_mode = NULL;
> >>  		struct drm_display_mode *newmode;
> >> -		u8 mode_idx = drm_match_cea_mode(mode) - 1;
> >> +		u8 vic = drm_match_cea_mode(mode);
> >>  		unsigned int clock1, clock2;
> >>  
> >> -		if (mode_idx < ARRAY_SIZE(edid_cea_modes)) {
> >> -			cea_mode = &edid_cea_modes[mode_idx];
> >> +		if (vic > 0 && vic < ARRAY_SIZE(edid_cea_modes)) {
> >
> > Maybe add some sort of vic_is_valid() helpers to avoid duplicating
> > these in so many places?
> 
> Any thoughts on how that should handle CEA vs. HDMI VICs, comparing
> against ARRAY_SIZE(edid_cea_modes) and ARRAY_SIZE(edid_4k_modes)?

I was thinking one function for each type, and yeah just

return vic != 0 && vic < ARRAY_SIZE(whatever_modes);

or something along those lines.

> 
> Add versions of drm_match_*_mode*() that return struct drm_display_mode
> * or NULL on errors?

Some time ago I was readin the DP spec, and ended up sketching out
some functions that might help deal with EDIDless DP branch devices.
For that I cooked up a function to return a pointer to the appropriate
CEA mode based on the vic (or NULL for bad vics). So I guess if you did
something like that + take the already existing match function, you
could wrap them in a neat package that returns the matching cea mode
for whatever mode is passed in.

> 
> BR,
> Jani.
> 
> 
> >
> > Otherwise I like it.
> >
> >> +			cea_mode = &edid_cea_modes[vic];
> >>  			clock2 = cea_mode_alternate_clock(cea_mode);
> >>  		} else {
> >> -			mode_idx = drm_match_hdmi_mode(mode) - 1;
> >> -			if (mode_idx < ARRAY_SIZE(edid_4k_modes)) {
> >> -				cea_mode = &edid_4k_modes[mode_idx];
> >> +			vic = drm_match_hdmi_mode(mode);
> >> +			if (vic > 0 && vic < ARRAY_SIZE(edid_4k_modes)) {
> >> +				cea_mode = &edid_4k_modes[vic];
> >>  				clock2 = hdmi_mode_alternate_clock(cea_mode);
> >>  			}
> >>  		}
> >> @@ -2773,17 +2776,17 @@ drm_display_mode_from_vic_index(struct drm_connector *connector,
> >>  {
> >>  	struct drm_device *dev = connector->dev;
> >>  	struct drm_display_mode *newmode;
> >> -	u8 cea_mode;
> >> +	u8 vic;
> >>  
> >>  	if (video_db == NULL || video_index >= video_len)
> >>  		return NULL;
> >>  
> >>  	/* CEA modes are numbered 1..127 */
> >> -	cea_mode = (video_db[video_index] & 127) - 1;
> >> -	if (cea_mode >= ARRAY_SIZE(edid_cea_modes))
> >> +	vic = (video_db[video_index] & 127);
> >> +	if (vic == 0 || vic >= ARRAY_SIZE(edid_cea_modes))
> >>  		return NULL;
> >>  
> >> -	newmode = drm_mode_duplicate(dev, &edid_cea_modes[cea_mode]);
> >> +	newmode = drm_mode_duplicate(dev, &edid_cea_modes[vic]);
> >>  	if (!newmode)
> >>  		return NULL;
> >>  
> >> @@ -2878,8 +2881,7 @@ static int add_hdmi_mode(struct drm_connector *connector, u8 vic)
> >>  	struct drm_device *dev = connector->dev;
> >>  	struct drm_display_mode *newmode;
> >>  
> >> -	vic--; /* VICs start at 1 */
> >> -	if (vic >= ARRAY_SIZE(edid_4k_modes)) {
> >> +	if (vic == 0 || vic >= ARRAY_SIZE(edid_4k_modes)) {
> >>  		DRM_ERROR("Unknown HDMI VIC: %d\n", vic);
> >>  		return 0;
> >>  	}
> >> @@ -3170,24 +3172,24 @@ static void fixup_detailed_cea_mode_clock(struct drm_display_mode *mode)
> >>  {
> >>  	const struct drm_display_mode *cea_mode;
> >>  	int clock1, clock2, clock;
> >> -	u8 mode_idx;
> >> +	u8 vic;
> >>  	const char *type;
> >>  
> >>  	/*
> >>  	 * allow 5kHz clock difference either way to account for
> >>  	 * the 10kHz clock resolution limit of detailed timings.
> >>  	 */
> >> -	mode_idx = drm_match_cea_mode_clock_tolerance(mode, 5) - 1;
> >> -	if (mode_idx < ARRAY_SIZE(edid_cea_modes)) {
> >> +	vic = drm_match_cea_mode_clock_tolerance(mode, 5);
> >> +	if (vic > 0 && vic < ARRAY_SIZE(edid_cea_modes)) {
> >>  		type = "CEA";
> >> -		cea_mode = &edid_cea_modes[mode_idx];
> >> +		cea_mode = &edid_cea_modes[vic];
> >>  		clock1 = cea_mode->clock;
> >>  		clock2 = cea_mode_alternate_clock(cea_mode);
> >>  	} else {
> >> -		mode_idx = drm_match_hdmi_mode_clock_tolerance(mode, 5) - 1;
> >> -		if (mode_idx < ARRAY_SIZE(edid_4k_modes)) {
> >> +		vic = drm_match_hdmi_mode_clock_tolerance(mode, 5);
> >> +		if (vic > 0 && vic < ARRAY_SIZE(edid_4k_modes)) {
> >>  			type = "HDMI";
> >> -			cea_mode = &edid_4k_modes[mode_idx];
> >> +			cea_mode = &edid_4k_modes[vic];
> >>  			clock1 = cea_mode->clock;
> >>  			clock2 = hdmi_mode_alternate_clock(cea_mode);
> >>  		} else {
> >> @@ -3205,7 +3207,7 @@ static void fixup_detailed_cea_mode_clock(struct drm_display_mode *mode)
> >>  		return;
> >>  
> >>  	DRM_DEBUG("detailed mode matches %s VIC %d, adjusting clock %d -> %d\n",
> >> -		  type, mode_idx + 1, mode->clock, clock);
> >> +		  type, vic, mode->clock, clock);
> >>  	mode->clock = clock;
> >>  }
> >>  
> >> -- 
> >> 2.1.4
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center

-- 
Ville Syrjälä
Intel OTC
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