[PATCH] drm/edid: support Microsoft extension for HMDs and specialized monitors

[Jani Nikula]

On Mon, 13 Dec 2021, Philipp Zabel <philipp.zabel at gmail.com> wrote:
> Add minimal support for parsing VSDBs documented in Microsoft's "EDID
> extension for head-mounted and specialized monitors" [1]. The version
> field and the desktop usage flag can be used to set the non_desktop
> connector property.
>
> Remove the non-desktop quirk for devices that are verified to contain
> the VSDB: HPN-3515 and LEN-B800. Presumably most of the other Windows
> Mixed Reality headsets contain it as well, but there are ACR-7FCE and
> SEC-5194 devices without it.
>
> [1] https://docs.microsoft.com/en-us/windows-hardware/drivers/display/specialized-monitors-edid-extension
>
> Tested with HPN-36C1 and LEN-B800.
>
> Signed-off-by: Philipp Zabel <philipp.zabel at gmail.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 36 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 12893e7be89b..baea65dfff7d 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -93,6 +93,8 @@ static int oui(u8 first, u8 second, u8 third)
>  /* Non desktop display (i.e. HMD) */
>  #define EDID_QUIRK_NON_DESKTOP			(1 << 12)
>  
> +#define MICROSOFT_IEEE_OUI	0xca125c
> +
>  struct detailed_mode_closure {
>  	struct drm_connector *connector;
>  	struct edid *edid;
> @@ -212,9 +214,7 @@ static const struct edid_quirk {
>  
>  	/* Windows Mixed Reality Headsets */
>  	EDID_QUIRK('A', 'C', 'R', 0x7fce, EDID_QUIRK_NON_DESKTOP),
> -	EDID_QUIRK('H', 'P', 'N', 0x3515, EDID_QUIRK_NON_DESKTOP),
>  	EDID_QUIRK('L', 'E', 'N', 0x0408, EDID_QUIRK_NON_DESKTOP),
> -	EDID_QUIRK('L', 'E', 'N', 0xb800, EDID_QUIRK_NON_DESKTOP),

Nitpick, in general I'd prefer the quirk removal to be a separate patch,
but not a big issue here.

>  	EDID_QUIRK('F', 'U', 'J', 0x1970, EDID_QUIRK_NON_DESKTOP),
>  	EDID_QUIRK('D', 'E', 'L', 0x7fce, EDID_QUIRK_NON_DESKTOP),
>  	EDID_QUIRK('S', 'E', 'C', 0x144a, EDID_QUIRK_NON_DESKTOP),
> @@ -4222,6 +4222,17 @@ static bool cea_db_is_hdmi_forum_vsdb(const u8 *db)
>  	return oui(db[3], db[2], db[1]) == HDMI_FORUM_IEEE_OUI;
>  }
>  
> +static bool cea_db_is_microsoft_vsdb(const u8 *db)
> +{
> +	if (cea_db_tag(db) != VENDOR_BLOCK)
> +		return false;
> +
> +	if (cea_db_payload_len(db) != 21)
> +		return false;
> +
> +	return oui(db[3], db[2], db[1]) == MICROSOFT_IEEE_OUI;
> +}
> +
>  static bool cea_db_is_vcdb(const u8 *db)
>  {
>  	if (cea_db_tag(db) != USE_EXTENDED_TAG)
> @@ -5149,6 +5160,25 @@ drm_parse_hdmi_vsdb_video(struct drm_connector *connector, const u8 *db)
>  	drm_parse_hdmi_deep_color_info(connector, db);
>  }
>  
> +/*
> + * See EDID extension for head-mounted and specialized monitors, specified at:
> + * https://docs.microsoft.com/en-us/windows-hardware/drivers/display/specialized-monitors-edid-extension
> + */
> +static void drm_parse_microsoft_vsdb(struct drm_connector *connector,
> +				     const u8 *db)
> +{
> +	struct drm_display_info *info = &connector->display_info;
> +	u8 version = db[4];
> +	bool desktop_usage = db[5] & BIT(6);
> +
> +	/* Version 1 and 2 for HMDs, version 3 flags desktop usage explicitly */
> +	if (version == 1 || version == 2 || (version == 3 && !desktop_usage))
> +		info->non_desktop = 1;

Nitpick, bool should be set to true instead of 1.

With this one fixed,

Reviewed-by: Jani Nikula <jani.nikula at intel.com>

I'll also reply with a follow-up patch that I think improves the logging
between this and the quirk.


BR,
Jani.


> +
> +	drm_dbg_kms(connector->dev, "HMD or specialized display VSDB version %u: 0x%02x\n",
> +		    version, db[5]);
> +}
> +
>  static void drm_parse_cea_ext(struct drm_connector *connector,
>  			      const struct edid *edid)
>  {
> @@ -5179,6 +5209,8 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
>  			drm_parse_hdmi_vsdb_video(connector, db);
>  		if (cea_db_is_hdmi_forum_vsdb(db))
>  			drm_parse_hdmi_forum_vsdb(connector, db);
> +		if (cea_db_is_microsoft_vsdb(db))
> +			drm_parse_microsoft_vsdb(connector, db);
>  		if (cea_db_is_y420cmdb(db))
>  			drm_parse_y420cmdb_bitmap(connector, db);
>  		if (cea_db_is_vcdb(db))
>
> base-commit: fa55b7dcdc43c1aa1ba12bca9d2dd4318c2a0dbf

-- 
Jani Nikula, Intel Open Source Graphics Center