[PATCH v3 1/6] drm/client: Add drm_client_init_from_id()

[Noralf Trønnes <noralf@xxxxxxxxxxx>]

drm_client_init_from_id() provides a way for clients to add a client based
on the minor. drm_client_register() is changed to return whether it was
registered or not depending on the unplugged status of the DRM device.
Its only caller drm_fbdev_generic_setup() runs inside probe() so it
doesn't have to check.

v2:
- Move drm_client_modeset_set() to a separate patch with added functions.
- Previous version had drm_client_init_from_id() call
  drm_client_register(). This put the client in a position where it could
  receive hotplugs during init in addition to akward error paths. Instead
  let drm_client_register() return status so clients can know if the DRM
  device is gone or not.

v3:
- Forgot to remove locking with the change in the previous version.
  No need for locking when drm_client_register() is not called.

Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
---
 drivers/gpu/drm/drm_client.c | 44 +++++++++++++++++++++++++++++++++++-
 include/drm/drm_client.h     |  4 +++-
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index 8f3d08dc996d..b7a310fef7e2 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -112,6 +112,36 @@ int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,
 }
 EXPORT_SYMBOL(drm_client_init);
 
+/**
+ * drm_client_init_from_id - Initialise a DRM client
+ * @minor_id: DRM minor id
+ * @client: DRM client
+ * @name: Client name
+ * @funcs: DRM client functions (optional)
+ *
+ * This function looks up the drm_device using the minor id and initializes the
+ * client using drm_client_init().
+ *
+ * Returns:
+ * Zero on success or negative error code on failure.
+ */
+int drm_client_init_from_id(unsigned int minor_id, struct drm_client_dev *client,
+			    const char *name, const struct drm_client_funcs *funcs)
+{
+	struct drm_minor *minor;
+	int ret;
+
+	minor = drm_minor_acquire(minor_id);
+	if (IS_ERR(minor))
+		return PTR_ERR(minor);
+
+	ret = drm_client_init(minor->dev, client, name, funcs);
+	drm_minor_release(minor);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_client_init_from_id);
+
 /**
  * drm_client_register - Register client
  * @client: DRM client
@@ -121,14 +151,26 @@ EXPORT_SYMBOL(drm_client_init);
  * drm_client_register() it is no longer permissible to call drm_client_release()
  * directly (outside the unregister callback), instead cleanup will happen
  * automatically on driver unload.
+ *
+ * Returns:
+ * True if the client has been registered, false if the DRM device has already
+ * been unregistered.
  */
-void drm_client_register(struct drm_client_dev *client)
+bool drm_client_register(struct drm_client_dev *client)
 {
 	struct drm_device *dev = client->dev;
+	int idx;
+
+	if (!drm_dev_enter(client->dev, &idx))
+		return false;
 
 	mutex_lock(&dev->clientlist_mutex);
 	list_add(&client->list, &dev->clientlist);
 	mutex_unlock(&dev->clientlist_mutex);
+
+	drm_dev_exit(idx);
+
+	return true;
 }
 EXPORT_SYMBOL(drm_client_register);
 
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
index 9f5a36a8ef24..76704f48fc46 100644
--- a/include/drm/drm_client.h
+++ b/include/drm/drm_client.h
@@ -109,8 +109,10 @@ struct drm_client_dev {
 
 int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,
 		    const char *name, const struct drm_client_funcs *funcs);
+int drm_client_init_from_id(unsigned int minor_id, struct drm_client_dev *client,
+			    const char *name, const struct drm_client_funcs *funcs);
 void drm_client_release(struct drm_client_dev *client);
-void drm_client_register(struct drm_client_dev *client);
+bool drm_client_register(struct drm_client_dev *client);
 
 void drm_client_dev_unregister(struct drm_device *dev);
 void drm_client_dev_hotplug(struct drm_device *dev);
-- 
2.23.0