Some state is coupled into the device lifetime outside of the
load/unload timeframe and requires teardown during final unreference
from drm_dev_release(). For example, dmabufs hold both a device and
module reference and may live longer than expected (i.e. the current
pattern of the driver tearing down its state and then releasing a
reference to the drm device) and yet touch driver private state when
destroyed.

v2: Export drm_dev_fini() and move the responsible for finalizing the
drm_device and freeing it to the release callback. (If no callback is
provided, the core will call drm_dev_fini() and kfree(dev) as before.)
v3: Remember to add drm_dev_fini() to drm_drv.h

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
---
 drivers/gpu/drm/drm_drv.c | 56 +++++++++++++++++++++++++++++++++--------------
 include/drm/drm_drv.h     | 11 ++++++++++
 2 files changed, 50 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 1b11ab628da7..517718e4f6e4 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -553,6 +553,39 @@ int drm_dev_init(struct drm_device *dev,
 EXPORT_SYMBOL(drm_dev_init);
 
 /**
+ * drm_dev_fini - Finalize a dead DRM device
+ * @dev: DRM device
+ *
+ * Finalize a dead DRM device. This is the converse to drm_dev_init() and
+ * frees up all state allocated by it. All driver state should be finalized
+ * first. Note that this function does not free the @dev, that is left to the
+ * caller. drm_dev_fini() should only
+ *
+ * The ref-count of @dev must be zero, and drm_dev_fini() should only be called
+ * from a drm_driver->release() callback.
+ */
+void drm_dev_fini(struct drm_device *dev)
+{
+       if (drm_core_check_feature(dev, DRIVER_GEM))
+               drm_gem_destroy(dev);
+
+       drm_legacy_ctxbitmap_cleanup(dev);
+       drm_ht_remove(&dev->map_hash);
+       drm_fs_inode_free(dev->anon_inode);
+
+       drm_minor_free(dev, DRM_MINOR_PRIMARY);
+       drm_minor_free(dev, DRM_MINOR_RENDER);
+       drm_minor_free(dev, DRM_MINOR_CONTROL);
+
+       mutex_destroy(&dev->master_mutex);
+       mutex_destroy(&dev->ctxlist_mutex);
+       mutex_destroy(&dev->filelist_mutex);
+       mutex_destroy(&dev->struct_mutex);
+       kfree(dev->unique);
+}
+EXPORT_SYMBOL(drm_dev_fini);
+
+/**
  * drm_dev_alloc - Allocate new DRM device
  * @driver: DRM driver to allocate device for
  * @parent: Parent device object
@@ -598,23 +631,12 @@ static void drm_dev_release(struct kref *ref)
 {
        struct drm_device *dev = container_of(ref, struct drm_device, ref);
 
-       if (drm_core_check_feature(dev, DRIVER_GEM))
-               drm_gem_destroy(dev);
-
-       drm_legacy_ctxbitmap_cleanup(dev);
-       drm_ht_remove(&dev->map_hash);
-       drm_fs_inode_free(dev->anon_inode);
-
-       drm_minor_free(dev, DRM_MINOR_PRIMARY);
-       drm_minor_free(dev, DRM_MINOR_RENDER);
-       drm_minor_free(dev, DRM_MINOR_CONTROL);
-
-       mutex_destroy(&dev->master_mutex);
-       mutex_destroy(&dev->ctxlist_mutex);
-       mutex_destroy(&dev->filelist_mutex);
-       mutex_destroy(&dev->struct_mutex);
-       kfree(dev->unique);
-       kfree(dev);
+       if (dev->driver->release) {
+               dev->driver->release(dev);
+       } else {
+               drm_dev_fini(dev);
+               kfree(dev);
+       }
 }
 
 /**
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 34ece393c639..bc5865ad0bbd 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -103,6 +103,15 @@ struct drm_driver {
         *
         */
        void (*unload) (struct drm_device *);
+
+       /**
+        * @release:
+        *
+        * Optional callback for destroying device state after the final
+        * reference is released, i.e. the device is being destroyed.
+        */
+       void (*release) (struct drm_device *);
+
        int (*dma_ioctl) (struct drm_device *dev, void *data, struct drm_file 
*file_priv);
        int (*dma_quiescent) (struct drm_device *);
        int (*context_dtor) (struct drm_device *dev, int context);
@@ -451,6 +460,8 @@ extern unsigned int drm_debug;
 int drm_dev_init(struct drm_device *dev,
                 struct drm_driver *driver,
                 struct device *parent);
+void drm_dev_fini(struct drm_device *dev);
+
 struct drm_device *drm_dev_alloc(struct drm_driver *driver,
                                 struct device *parent);
 int drm_dev_register(struct drm_device *dev, unsigned long flags);
-- 
2.11.0

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