drm: uevent for connector status change

DRM API for generating uevent for a status changes of connector's
property.

This uevent will have following details related to the status change:

HOTPLUG=1, CONNECTOR=<connector_id> and PROPERTY=<property_id>

Pekka have completed the Weston DRM-backend review in
https://gitlab.freedesktop.org/wayland/weston/merge_requests/48
and the UAPI for HDCP 2.2 looks good.

The userspace is accepted in Weston.

v2:
Minor fixes at KDoc comments [Daniel]
v3:
Check the property is really attached with connector [Daniel]
v4:
Typos and string length suggestions are addressed [Sean]

Signed-off-by: Ramalingam C <[e-mail]>
Reviewed-by: Daniel Vetter <[e-mail]>
Reviewed-by: Sean Paul <[e-mail]>
Acked-by: Pekka Paalanen <[e-mail]>
Acked-by: Jani Nikula <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/320961/?series=57232&rev=14

drivers/gpu/drm/drm_sysfs.c

···
 #include <drm/drm_sysfs.h>
 
 #include "drm_internal.h"
+#include "drm_crtc_internal.h"
 
 #define to_drm_minor(d) dev_get_drvdata(d)
 #define to_drm_connector(d) dev_get_drvdata(d)
···
  * Send a uevent for the DRM device specified by @dev.  Currently we only
  * set HOTPLUG=1 in the uevent environment, but this could be expanded to
  * deal with other types of events.
+ *
+ * Any new uapi should be using the drm_sysfs_connector_status_event()
+ * for uevents on connector status change.
  */
 void drm_sysfs_hotplug_event(struct drm_device *dev)
 {
···
 	kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
 }
 EXPORT_SYMBOL(drm_sysfs_hotplug_event);
+
+/**
+ * drm_sysfs_connector_status_event - generate a DRM uevent for connector
+ * property status change
+ * @connector: connector on which property status changed
+ * @property: connector property whose status changed.
+ *
+ * Send a uevent for the DRM device specified by @dev.  Currently we
+ * set HOTPLUG=1 and connector id along with the attached property id
+ * related to the status change.
+ */
+void drm_sysfs_connector_status_event(struct drm_connector *connector,
+				      struct drm_property *property)
+{
+	struct drm_device *dev = connector->dev;
+	char hotplug_str[] = "HOTPLUG=1", conn_id[21], prop_id[21];
+	char *envp[4] = { hotplug_str, conn_id, prop_id, NULL };
+
+	WARN_ON(!drm_mode_obj_find_prop_id(&connector->base,
+					   property->base.id));
+
+	snprintf(conn_id, ARRAY_SIZE(conn_id),
+		 "CONNECTOR=%u", connector->base.id);
+	snprintf(prop_id, ARRAY_SIZE(prop_id),
+		 "PROPERTY=%u", property->base.id);
+
+	DRM_DEBUG("generating connector status event\n");
+
+	kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
+}
+EXPORT_SYMBOL(drm_sysfs_connector_status_event);
 
 static void drm_sysfs_release(struct device *dev)
 {

include/drm/drm_sysfs.h

···
 
 struct drm_device;
 struct device;
+struct drm_connector;
+struct drm_property;
 
 int drm_class_device_register(struct device *dev);
 void drm_class_device_unregister(struct device *dev);
 
 void drm_sysfs_hotplug_event(struct drm_device *dev);
-
+void drm_sysfs_connector_status_event(struct drm_connector *connector,
+				      struct drm_property *property);
 #endif