drm/vkms: Allow to configure connector status via configfs

When a connector is created, add a `status` file to allow to update the
connector status to:

 - 1 connector_status_connected
 - 2 connector_status_disconnected
 - 3 connector_status_unknown

If the device is enabled, updating the status hot-plug or unplugs the
connector.

Tested-by: Mark Yacoub <markyacoub@google.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Link: https://lore.kernel.org/r/20251016175618.10051-17-jose.exposito89@gmail.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Author: JoseExposito

Documentation/gpu/vkms.rst

@@ -108,6 +108,11 @@ Last but not least, create one or more connectors::
 
   sudo mkdir /config/vkms/my-vkms/connectors/connector0
 
+Connectors have 1 configurable attribute:
+
+- status: Connection status: 1 connected, 2 disconnected, 3 unknown (same values
+  as those exposed by the "status" property of a connector)
+
 To finish the configuration, link the different pipeline items::
 
   sudo ln -s /config/vkms/my-vkms/crtcs/crtc0 /config/vkms/my-vkms/planes/plane0/possible_crtcs

drivers/gpu/drm/vkms/vkms_configfs.c

@@ -7,6 +7,7 @@
 #include "vkms_drv.h"
 #include "vkms_config.h"
 #include "vkms_configfs.h"
+#include "vkms_connector.h"
 
 /* To avoid registering configfs more than once or unregistering on error */
 static bool is_configfs_registered;
@@ -512,6 +513,52 @@ static const struct config_item_type encoder_group_type = {
 	.ct_owner	= THIS_MODULE,
 };
 
+static ssize_t connector_status_show(struct config_item *item, char *page)
+{
+	struct vkms_configfs_connector *connector;
+	enum drm_connector_status status;
+
+	connector = connector_item_to_vkms_configfs_connector(item);
+
+	scoped_guard(mutex, &connector->dev->lock)
+		status = vkms_config_connector_get_status(connector->config);
+
+	return sprintf(page, "%u", status);
+}
+
+static ssize_t connector_status_store(struct config_item *item,
+				      const char *page, size_t count)
+{
+	struct vkms_configfs_connector *connector;
+	enum drm_connector_status status;
+
+	connector = connector_item_to_vkms_configfs_connector(item);
+
+	if (kstrtouint(page, 10, &status))
+		return -EINVAL;
+
+	if (status != connector_status_connected &&
+	    status != connector_status_disconnected &&
+	    status != connector_status_unknown)
+		return -EINVAL;
+
+	scoped_guard(mutex, &connector->dev->lock) {
+		vkms_config_connector_set_status(connector->config, status);
+
+		if (connector->dev->enabled)
+			vkms_trigger_connector_hotplug(connector->dev->config->dev);
+	}
+
+	return (ssize_t)count;
+}
+
+CONFIGFS_ATTR(connector_, status);
+
+static struct configfs_attribute *connector_item_attrs[] = {
+	&connector_attr_status,
+	NULL,
+};
+
 static void connector_release(struct config_item *item)
 {
 	struct vkms_configfs_connector *connector;
@@ -531,6 +578,7 @@ static struct configfs_item_operations connector_item_operations = {
 };
 
 static const struct config_item_type connector_item_type = {
+	.ct_attrs	= connector_item_attrs,
 	.ct_item_ops	= &connector_item_operations,
 	.ct_owner	= THIS_MODULE,
 };

drivers/gpu/drm/vkms/vkms_connector.c

@@ -87,3 +87,10 @@ struct vkms_connector *vkms_connector_init(struct vkms_device *vkmsdev)
 
 	return connector;
 }
+
+void vkms_trigger_connector_hotplug(struct vkms_device *vkmsdev)
+{
+	struct drm_device *dev = &vkmsdev->drm;
+
+	drm_kms_helper_hotplug_event(dev);
+}

drivers/gpu/drm/vkms/vkms_connector.h

@@ -26,4 +26,10 @@ struct vkms_connector {
  */
 struct vkms_connector *vkms_connector_init(struct vkms_device *vkmsdev);
 
+/**
+ * vkms_trigger_connector_hotplug() - Update the device's connectors status
+ * @vkmsdev: VKMS device to update
+ */
+void vkms_trigger_connector_hotplug(struct vkms_device *vkmsdev);
+
 #endif /* _VKMS_CONNECTOR_H_ */