Re: [PATCH 2/7] drm/i915: Extract intel_dp_has_dsc()

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 20 May 2024, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Mon, May 20, 2024 at 01:47:34PM +0300, Jani Nikula wrote:
>> On Fri, 17 May 2024, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
>> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> >
>> > Extract a helper to check whether the source+sink combo
>> > supports DSC. That basic check is needed both during mode
>> > validation and compute config. We'll also need to add extra
>> > checks to both places, so having a single place for it is nicer.
>> >
>> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/display/intel_dp.c | 16 ++++++++++++++--
>> >  1 file changed, 14 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> > index 1e88449fe5f2..7bf283b4df7f 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> > @@ -1220,6 +1220,19 @@ bool intel_dp_need_bigjoiner(struct intel_dp *intel_dp,
>> >  	       connector->force_bigjoiner_enable;
>> >  }
>> >  
>> > +static bool intel_dp_has_dsc(struct intel_connector *connector)
>> 
>> Why not const?
>
> We've generally not consted these things. And then whenver add
> one const somewhere it usually ends up getting in the way later,
> not because we need mutability but simply because we want to
> call something that doesn't have the const.
>
> I suppose if we do want to start consting things more we should
> just do some kind of bigger pass over the whole codebase so that
> that there's less chance of pain later.
>
> We're also not using container_of_const() for these right now,
> so the const can vanish semi-accidentally when casting things.
>
> I suppose this thing might be low level enough that the const
> could be kept. I'll have another think about it.

It's just that this series drops a bunch of const because of this, which
feels like the opposite of what you usually do. :)

BR,
Jani.


>
>> 
>> > +{
>> > +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
>> > +
>> > +	if (!HAS_DSC(i915))
>> > +		return false;
>> > +
>> > +	if (!drm_dp_sink_supports_dsc(connector->dp.dsc_dpcd))
>> > +		return false;
>> > +
>> > +	return true;
>> > +}
>> > +
>> >  static enum drm_mode_status
>> >  intel_dp_mode_valid(struct drm_connector *_connector,
>> >  		    struct drm_display_mode *mode)
>> > @@ -1274,8 +1287,7 @@ intel_dp_mode_valid(struct drm_connector *_connector,
>> >  	mode_rate = intel_dp_link_required(target_clock,
>> >  					   intel_dp_mode_min_output_bpp(connector, mode));
>> >  
>> > -	if (HAS_DSC(dev_priv) &&
>> > -	    drm_dp_sink_supports_dsc(connector->dp.dsc_dpcd)) {
>> > +	if (intel_dp_has_dsc(connector)) {
>> >  		enum intel_output_format sink_format, output_format;
>> >  		int pipe_bpp;
>> 
>> -- 
>> Jani Nikula, Intel

-- 
Jani Nikula, Intel