drm/bridge: introduce bridge detaching mechanism

Up to now, once a bridge has been attached to a DRM device, it cannot
be undone.

In particular you couldn't rmmod/insmod a DRM driver that uses a bridge,
because the bridge would remain bound to the first (dead) driver instance.

This patch fixes this by introducing drm_encoder_detach() and a ->detach
callback in drm_bridge_funcs for the bridge to be notified about detaches.

It's DRM/KMS driver responsibility to call drm_encoder_detach().

While adding the bridge detach callback, with its kerneldoc, I also added
kerneldoc for attach callback.

Few other kerneldocs fixes around there are included.

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Suggested-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1472115874-6219-1-git-send-email-andrea.merello@gmail.com

1 files changed, 27 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 255543086590..484046664d6c 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -98,11 +98,11 @@ EXPORT_SYMBOL(drm_bridge_remove);
  * @dev: DRM device
  * @bridge: bridge control structure
  *
- * called by a kms driver to link one of our encoder/bridge to the given
+ * Called by a kms driver to link one of our encoder/bridge to the given
  * bridge.
  *
  * Note that setting up links between the bridge and our encoder/bridge
- * objects needs to be handled by the kms driver itself
+ * objects needs to be handled by the kms driver itself.
  *
  * RETURNS:
  * Zero on success, error code on failure
@@ -125,6 +125,31 @@ int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge)
 EXPORT_SYMBOL(drm_bridge_attach);
 
 /**
+ * drm_bridge_detach - deassociate given bridge from its DRM device
+ *
+ * @bridge: bridge control structure
+ *
+ * Called by a kms driver to unlink the given bridge from its DRM device.
+ *
+ * Note that tearing down links between the bridge and our encoder/bridge
+ * objects needs to be handled by the kms driver itself.
+ */
+void drm_bridge_detach(struct drm_bridge *bridge)
+{
+	if (WARN_ON(!bridge))
+		return;
+
+	if (WARN_ON(!bridge->dev))
+		return;
+
+	if (bridge->funcs->detach)
+		bridge->funcs->detach(bridge);
+
+	bridge->dev = NULL;
+}
+EXPORT_SYMBOL(drm_bridge_detach);
+
+/**
  * DOC: bridge callbacks
  *
  * The &drm_bridge_funcs ops are populated by the bridge driver. The DRM