[PATCH v2 1/3] drm/bridge: introduce bridge detaching mechanism

[Andrea Merello]

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.

Suggested-by: Daniel Vetter <daniel at ffwll.ch>
Suggested-by: Lucas Stach <l.stach at pengutronix.de>
Signed-off-by: Andrea Merello <andrea.merello at gmail.com>
Cc: Archit Taneja <architt at codeaurora.org>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Lucas Stach <l.stach at pengutronix.de>
---
 drivers/gpu/drm/drm_bridge.c | 26 ++++++++++++++++++++++++++
 include/drm/drm_crtc.h       | 17 +++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 2555430..a77b3e0 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -125,6 +125,32 @@ 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
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index b618b50..5e25e23 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -1765,9 +1765,25 @@ struct drm_plane {
  * @attach: Called during drm_bridge_attach
  */
 struct drm_bridge_funcs {
+	/**
+	 * @attach:
+	 *
+	 * This callback is invoked whenever our bridge is being attached.
+	 *
+	 * RETURNS:
+	 *
+	 * Zero on success, error code on failure
+	 */
 	int (*attach)(struct drm_bridge *bridge);
 
 	/**
+	 * @detach:
+	 *
+	 * This callback is invoked whenever our bridge is being detached.
+	 */
+	void (*detach)(struct drm_bridge *bridge);
+
+	/**
 	 * @mode_fixup:
 	 *
 	 * This callback is used to validate and adjust a mode. The paramater
@@ -3196,6 +3212,7 @@ extern int drm_bridge_add(struct drm_bridge *bridge);
 extern void drm_bridge_remove(struct drm_bridge *bridge);
 extern struct drm_bridge *of_drm_find_bridge(struct device_node *np);
 extern int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge);
+extern void drm_bridge_detach(struct drm_bridge *bridge);
 
 bool drm_bridge_mode_fixup(struct drm_bridge *bridge,
 			const struct drm_display_mode *mode,
-- 
2.7.4