[PATCH 2/6] drm/drv: Prepare to remove drm_dev_unplug()

["Noralf Trønnes" <noralf@tronnes.org>]

The only thing now that makes drm_dev_unplug() special is that it sets
drm_device->unplugged. Move this code to drm_dev_unregister() so that we
can remove drm_dev_unplug().

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---

Maybe s/unplugged/unregistered/ ?

I looked at drm_device->registered, but using that would mean that
drm_dev_is_unplugged() would return before drm_device is registered.
And given that its current purpose is to prevent race against connector
registration, I stayed away from it.

Noralf.


 drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------
 include/drm/drm_drv.h     | 10 ++++------
 2 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 05bbc2b622fc..e0941200edc6 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit);
  */
 void drm_dev_unplug(struct drm_device *dev)
 {
-	/*
-	 * After synchronizing any critical read section is guaranteed to see
-	 * the new value of ->unplugged, and any critical section which might
-	 * still have seen the old value of ->unplugged is guaranteed to have
-	 * finished.
-	 */
-	dev->unplugged = true;
-	synchronize_srcu(&drm_unplug_srcu);
-
 	drm_dev_unregister(dev);
 	drm_dev_put(dev);
 }
@@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
  * drm_dev_register() but does not deallocate the device. The caller must call
  * drm_dev_put() to drop their final reference.
  *
- * A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- * which can be called while there are still open users of @dev.
+ * This function can be called while there are still open users of @dev as long
+ * as the driver protects its device resources using drm_dev_enter() and
+ * drm_dev_exit().
  *
  * This should be called first in the device teardown code to make sure
- * userspace can't access the device instance any more.
+ * userspace can't access the device instance any more. Drivers that support
+ * device unplug will probably want to call drm_atomic_helper_shutdown() first
+ * in order to disable the hardware on regular driver module unload.
  */
 void drm_dev_unregister(struct drm_device *dev)
 {
@@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev)
 	if (drm_core_check_feature(dev, DRIVER_LEGACY))
 		drm_lastclose(dev);
 
+	/*
+	 * After synchronizing any critical read section is guaranteed to see
+	 * the new value of ->unplugged, and any critical section which might
+	 * still have seen the old value of ->unplugged is guaranteed to have
+	 * finished.
+	 */
+	dev->unplugged = true;
+	synchronize_srcu(&drm_unplug_srcu);
+
 	dev->registered = false;
 
 	drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index ca46a45a9cce..c50696c82a42 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
  * drm_dev_is_unplugged - is a DRM device unplugged
  * @dev: DRM device
  *
- * This function can be called to check whether a hotpluggable is unplugged.
- * Unplugging itself is singalled through drm_dev_unplug(). If a device is
- * unplugged, these two functions guarantee that any store before calling
- * drm_dev_unplug() is visible to callers of this function after it completes
+ * This function can be called to check whether @dev is unregistered. This can
+ * be used to detect that the underlying parent device is gone.
  *
- * WARNING: This function fundamentally races against drm_dev_unplug(). It is
- * recommended that drivers instead use the underlying drm_dev_enter() and
+ * WARNING: This function fundamentally races against drm_dev_unregister(). It
+ * is recommended that drivers instead use the underlying drm_dev_enter() and
  * drm_dev_exit() function pairs.
  */
 static inline bool drm_dev_is_unplugged(struct drm_device *dev)
-- 
2.20.1

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