[PATCH 2/4 v3] drm: Introduce drm_connector_register_all() helper

[Alexey Brodkin <Alexey.Brodkin@synopsys.com>]

As a pair to already existing drm_connector_unregister_all() we're adding
generic implementation of what is already done in some drivers.

Once this helper is implemented we'll be ready to switch existing
driver-specific implementations with the generic one.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
---

Changes v2 -> v3:
 * Updated title with capital after colon
 * Simplified failure path with direct and unconditional invocation of
   unregister_all()
 * Updated kerneldoc description of the drm_connector_register_all()

Changes v1 -> v2:
 * Rename drm_connector_unplug_all() to drm_connector_unregister_all()
 * Use drm_for_each_connector() instead of list_for_each_entry()
 * Updated kerneldoc for drm_dev_register()

 drivers/gpu/drm/drm_crtc.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_drv.c  |  6 +++++-
 include/drm/drm_crtc.h     |  3 ++-
 3 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 65488a6..21eea11 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1081,6 +1081,49 @@ void drm_connector_unregister(struct drm_connector *connector)
 EXPORT_SYMBOL(drm_connector_unregister);
 
 /**
+ * drm_connector_register_all - register all connectors
+ * @dev: drm device
+ *
+ * This function registers all connectors in sysfs and other places so that
+ * userspace can start to access them. Drivers can call it after calling
+ * drm_dev_register() to complete the device registration, if they don't call
+ * drm_connector_register() on each connector individually.
+ *
+ * When a device is unplugged and should be removed from userspace access,
+ * call drm_connector_unregister_all(), which is the inverse of this
+ * function.
+ *
+ * Returns:
+ * Zero on success, error code on failure.
+ */
+int drm_connector_register_all(struct drm_device *dev)
+{
+	struct drm_connector *connector;
+	int ret;
+
+	mutex_lock(&dev->mode_config.mutex);
+
+	drm_for_each_connector(connector, dev) {
+		ret = drm_connector_register(connector);
+		if (ret) {
+			/*
+			 * We may safely call unregister_all() here within
+			 * area locked with mutex because unregister_all()
+			 * doesn't use locks inside (see a comment in that
+			 * function).
+			 */
+			drm_connector_unregister_all(dev);
+			return ret;
+		}
+	}
+
+	mutex_unlock(&dev->mode_config.mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_connector_register_all);
+
+/**
  * drm_connector_unregister_all - unregister connector userspace interfaces
  * @dev: drm device
  *
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 167c8d3..2c9a2b6 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -715,7 +715,11 @@ EXPORT_SYMBOL(drm_dev_unref);
  *
  * Register the DRM device @dev with the system, advertise device to user-space
  * and start normal device operation. @dev must be allocated via drm_dev_alloc()
- * previously.
+ * previously. Right after drm_dev_register() the driver should call
+ * drm_connector_register_all() to register all connectors in sysfs. This is
+ * a separate call for backward compatibility with drivers still using
+ * the deprecated ->load() callback, where connectors are registered from within
+ * the ->load() callback.
  *
  * Never call this twice on any device!
  *
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 42d9f4d..6a34117 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -2214,7 +2214,8 @@ void drm_connector_unregister(struct drm_connector *connector);
 
 extern void drm_connector_cleanup(struct drm_connector *connector);
 extern unsigned int drm_connector_index(struct drm_connector *connector);
-/* helper to unregister all connectors from sysfs for device */
+/* helpers to {un}register all connectors from sysfs for device */
+extern int drm_connector_register_all(struct drm_device *dev);
 extern void drm_connector_unregister_all(struct drm_device *dev);
 
 extern int drm_bridge_add(struct drm_bridge *bridge);
-- 
2.5.0