[PATCH v2 08/27] drm/connector: Add drm_display_info_is_vrr_capable

[Nicolas Frattaroli <nicolas.frattaroli@collabora.com>]

Add a function to return whether a sink, as described by a
drm_display_info struct, is capable of receiving VRR signals.

For HDMI sinks, this can just check the HDMI specific vrr_cap.supported
field, which is set by the EDID parsing code. For other types of
displays, the generally agreed-upon method appears to be to check
whether the monitor range's minimum frequency is above 0.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
 drivers/gpu/drm/drm_connector.c | 19 +++++++++++++++++++
 include/drm/drm_connector.h     |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 65c14b6e47a6..a44afba8c5ff 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -1378,6 +1378,25 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
 }
 EXPORT_SYMBOL(drm_display_info_set_bus_formats);
 
+/**
+ * drm_display_info_is_vrr_capable - Check whether sink is VRR capable
+ * @info: pointer to a &struct drm_display_info representing the sink
+ *
+ * Check whether the sink supports variable refresh rate signals.
+ *
+ * Returns:
+ * - true if variable refresh rate is supported by the sink
+ * - false otherwise
+ */
+bool drm_display_info_is_vrr_capable(const struct drm_display_info *info)
+{
+	if (info->is_hdmi)
+		return info->hdmi.vrr_cap.supported;
+
+	return info->monitor_range.min_vfreq > 0;
+}
+EXPORT_SYMBOL(drm_display_info_is_vrr_capable);
+
 /* Optional connector properties. */
 static const struct drm_prop_enum_list drm_scaling_mode_enum_list[] = {
 	{ DRM_MODE_SCALE_NONE, "None" },
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 9df745ecff92..5b6920c1a996 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1078,6 +1078,8 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
 				     const u32 *formats,
 				     unsigned int num_formats);
 
+bool drm_display_info_is_vrr_capable(const struct drm_display_info *info);
+
 /**
  * struct drm_connector_tv_margins - TV connector related margins
  *

-- 
2.56.0