Re: [PATCH v2 06/18] drm/dp: Add helpers to identify downstream facing port types

[Lyude Paul <lyude@redhat.com>]

On Fri, 2020-09-04 at 14:53 +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Add a few helpers to let us better identify which kind of DFP
> we're dealing with.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 60 +++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h     |  5 +++
>  2 files changed, 65 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c
> b/drivers/gpu/drm/drm_dp_helper.c
> index c21bbfc3d714..0fcb94f7dbe5 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -363,6 +363,66 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux
> *aux,
>  }
>  EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
>  
> +static bool is_edid_digital_input_dp(const struct edid *edid)
> +{
> +	return edid && edid->revision >= 4 &&
> +		edid->input & DRM_EDID_INPUT_DIGITAL &&
> +		(edid->input & DRM_EDID_DIGITAL_TYPE_MASK) ==
> DRM_EDID_DIGITAL_TYPE_DP;
> +}
> +
> +/**
> + * drm_dp_downstream_is_type() - is the downstream facing port of certain
> type?
> + * @dpcd: DisplayPort configuration data
> + * @port_cap: port capabilities
> + *
> + * Caveat: Only works with DPCD 1.1+ port caps.
> + *
> + * Returns whether the downstream facing port matches the type.

Nitpick: s/Returns/Returns:/ for kdoc purposes

> + */
> +bool drm_dp_downstream_is_type(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> +			       const u8 port_cap[4], u8 type)
> +{
> +	return drm_dp_is_branch(dpcd) &&
> +		dpcd[DP_DPCD_REV] >= 0x11 &&
> +		(port_cap[0] & DP_DS_PORT_TYPE_MASK) == type;
> +}
> +EXPORT_SYMBOL(drm_dp_downstream_is_type);
> +
> +/**
> + * drm_dp_downstream_is_tmds() - is the downstream facing port TMDS?
> + * @dpcd: DisplayPort configuration data
> + * @port_cap: port capabilities
> + * @edid: EDID
> + *
> + * Returns whether the downstream facing port is TMDS (HDMI/DVI).

Same nitpick here

> + */
> +bool drm_dp_downstream_is_tmds(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> +			       const u8 port_cap[4],
> +			       const struct edid *edid)
> +{
> +	if (dpcd[DP_DPCD_REV] < 0x11) {
> +		switch (dpcd[DP_DOWNSTREAMPORT_PRESENT] &
> DP_DWN_STRM_PORT_TYPE_MASK) {
> +		case DP_DWN_STRM_PORT_TYPE_TMDS:
> +			return true;
> +		default:
> +			return false;
> +		}
> +	}
> +
> +	switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
> +	case DP_DS_PORT_TYPE_DP_DUALMODE:
> +		if (is_edid_digital_input_dp(edid))
> +			return false;
> +		fallthrough;
> +	case DP_DS_PORT_TYPE_DVI:
> +	case DP_DS_PORT_TYPE_HDMI:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +EXPORT_SYMBOL(drm_dp_downstream_is_tmds);
> +
>  /**
>   * drm_dp_send_real_edid_checksum() - send back real edid checksum value
>   * @aux: DisplayPort AUX channel
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 86461a40066b..4f946826dfce 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1638,6 +1638,11 @@ bool drm_dp_send_real_edid_checksum(struct drm_dp_aux
> *aux,
>  int drm_dp_read_downstream_info(struct drm_dp_aux *aux,
>  				const u8 dpcd[DP_RECEIVER_CAP_SIZE],
>  				u8 downstream_ports[DP_MAX_DOWNSTREAM_PORTS]);
> +bool drm_dp_downstream_is_type(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> +			       const u8 port_cap[4], u8 type);
> +bool drm_dp_downstream_is_tmds(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> +			       const u8 port_cap[4],
> +			       const struct edid *edid);
>  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],
-- 
Cheers,
	Lyude Paul (she/her)
	Software Engineer at Red Hat

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