[PATCH] drm: Provide a driver hook for drm_dev_release()

[Chris Wilson]

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.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/drm_drv.c | 3 +++
 include/drm/drm_drv.h     | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index f74b7d06ec01..f945bbcc8eb3 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -595,6 +595,9 @@ static void drm_dev_release(struct kref *ref)
 {
        struct drm_device *dev = container_of(ref, struct drm_device, ref);

+       if (dev->driver->release)
+               dev->driver->release(dev);
+
        if (drm_core_check_feature(dev, DRIVER_GEM))
                drm_gem_destroy(dev);

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index c4fc49583dc0..554104ccb939 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -71,6 +71,14 @@ struct drm_driver {
        void (*postclose) (struct drm_device *, struct drm_file *);
        void (*lastclose) (struct drm_device *);
        int (*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);
-- 
2.11.0