Re: [PATCH v8 04/12] drm: Helper to read max bits per component

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

On Wed, Aug 17, 2016 at 01:49:40PM +0300, Mika Kahola wrote:
> Helper routine to read out maximum supported bits per
> component for DisplayPort legay converters.
> 
> v2: Return early if detailed port cap info is not available.
>     Replace if-else ladder with switch-case (Ville)
> 
> Reviewed-by: Jim Bride <jim.bride@linux.intel.com>
> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 42 +++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h     |  2 ++
>  2 files changed, 44 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 7497490..14e8ea0 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -472,6 +472,48 @@ int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
>  }
>  EXPORT_SYMBOL(drm_dp_downstream_max_clock);
>  
> +/**
> + * drm_dp_downstream_max_bpc() - extract branch device max
> + *                               bits per component
> + * @dpcd: DisplayPort configuration data
> + * @port_cap: port capabilities
> + *
> + * Returns max bpc on success or 0 if max bpc not defined
> + */
> +int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> +			      const u8 port_cap[4])
> +{
> +	int type = port_cap[0] & DP_DS_PORT_TYPE_MASK;
> +	bool detailed_cap_info = dpcd[DP_DOWNSTREAMPORT_PRESENT] &
> +		DP_DETAILED_CAP_INFO_AVAILABLE;
> +	int bpc;
> +
> +	if (!detailed_cap_info)
> +		return 0;
> +
> +	switch (type) {
> +	case DP_DS_PORT_TYPE_VGA:
> +	case DP_DS_PORT_TYPE_DVI:
> +	case DP_DS_PORT_TYPE_HDMI:
> +	case DP_DS_PORT_TYPE_DP_DUALMODE:

I think we might want return 8; for the detailed_cap_info==0 case with
these port types.

> +		bpc = port_cap[2] & DP_DS_MAX_BPC_MASK;
> +
> +		switch (bpc) {
> +		case DP_DS_8BPC:
> +			return 8;
> +		case DP_DS_10BPC:
> +			return 10;
> +		case DP_DS_12BPC:
> +			return 12;
> +		case DP_DS_16BPC:
> +			return 16;
> +		}
> +	default:
> +		return 0;
> +	}
> +}
> +EXPORT_SYMBOL(drm_dp_downstream_max_bpc);
> +
>  /*
>   * I2C-over-AUX implementation
>   */
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 60dd9dc..f3d1424 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -817,6 +817,8 @@ int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link);
>  int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
>  int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
>  				const u8 port_cap[4]);
> +int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> +			      const u8 port_cap[4]);
>  
>  void drm_dp_aux_init(struct drm_dp_aux *aux);
>  int drm_dp_aux_register(struct drm_dp_aux *aux);
> -- 
> 1.9.1

-- 
Ville Syrjälä
Intel OTC
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