drm: Lighten sysfs connector 'status'

Since the beginning, sysfs/connector/status has done a heavyweight
detection of the current connector status. But no user, such as upowerd
or logind, has ever desired to initiate a probe. Move the probing into a
new attribute so that existing readers get the behaviour they desire.

v2: David Herrmann suggested using "echo detect > /sys/.../status" to
trigger the probing, which is a fine idea. This extends that to also
allow the user to apply the force detection overrides at runtime.

v3: Now with airlied's email address fixed! Requires sysfs_streq()
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Alex Deucher <alexdeucher@gmail.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_sysfs.c

@@ -166,23 +166,68 @@ void drm_sysfs_destroy(void)
 /*
  * Connector properties
  */
-static ssize_t status_show(struct device *device,
+static ssize_t status_store(struct device *device,
 			   struct device_attribute *attr,
-			   char *buf)
+			   const char *buf, size_t count)
 {
 	struct drm_connector *connector = to_drm_connector(device);
-	enum drm_connector_status status;
+	struct drm_device *dev = connector->dev;
+	enum drm_connector_status old_status;
 	int ret;
 
-	ret = mutex_lock_interruptible(&connector->dev->mode_config.mutex);
+	ret = mutex_lock_interruptible(&dev->mode_config.mutex);
 	if (ret)
 		return ret;
 
-	status = connector->funcs->detect(connector, true);
-	mutex_unlock(&connector->dev->mode_config.mutex);
+	old_status = connector->status;
+
+	if (sysfs_streq(buf, "detect")) {
+		connector->force = 0;
+		connector->status = connector->funcs->detect(connector, true);
+	} else if (sysfs_streq(buf, "on")) {
+		connector->force = DRM_FORCE_ON;
+	} else if (sysfs_streq(buf, "on-digital")) {
+		connector->force = DRM_FORCE_ON_DIGITAL;
+	} else if (sysfs_streq(buf, "off")) {
+		connector->force = DRM_FORCE_OFF;
+	} else
+		ret = -EINVAL;
+
+	if (ret == 0 && connector->force) {
+		if (connector->force == DRM_FORCE_ON ||
+		    connector->force == DRM_FORCE_ON_DIGITAL)
+			connector->status = connector_status_connected;
+		else
+			connector->status = connector_status_disconnected;
+		if (connector->funcs->force)
+			connector->funcs->force(connector);
+	}
+
+	if (old_status != connector->status) {
+		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %d to %d\n",
+			      connector->base.id,
+			      connector->name,
+			      old_status, connector->status);
+
+		dev->mode_config.delayed_event = true;
+		if (dev->mode_config.poll_enabled)
+			schedule_delayed_work(&dev->mode_config.output_poll_work,
+					      0);
+	}
+
+	mutex_unlock(&dev->mode_config.mutex);
+
+	return ret;
+}
+
+static ssize_t status_show(struct device *device,
+			   struct device_attribute *attr,
+			   char *buf)
+{
+	struct drm_connector *connector = to_drm_connector(device);
 
 	return snprintf(buf, PAGE_SIZE, "%s\n",
-			drm_get_connector_status_name(status));
+			drm_get_connector_status_name(connector->status));
 }
 
 static ssize_t dpms_show(struct device *device,
@@ -339,7 +384,7 @@ static ssize_t select_subconnector_show(struct device *device,
 			drm_get_dvi_i_select_name((int)subconnector));
 }
 
-static DEVICE_ATTR_RO(status);
+static DEVICE_ATTR_RW(status);
 static DEVICE_ATTR_RO(enabled);
 static DEVICE_ATTR_RO(dpms);
 static DEVICE_ATTR_RO(modes);