drm: Provide a driver hook for drm_dev_release()

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 responsibility 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
v4: Tidy language for kerneldoc
v5: Cross reference from drm_dev_init() to note that driver->release()
allows for arbitrary embedding.
v6: Refer to driver data rather than driver state, as state is now
becoming associated with the struct drm_atomic_state and friends.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[danvet: Use the proper reference for struct members, which is
&drm_driver.release.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170202093632.31017-1-chris@chris-wilson.co.uk

1 files changed, 13 insertions, 0 deletions

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 732e85652d1e..5699f42195fe 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -102,6 +102,17 @@ struct drm_driver {
 	 *
 	 */
 	void (*unload) (struct drm_device *);
+
+	/**
+	 * @release:
+	 *
+	 * Optional callback for destroying device data after the final
+	 * reference is released, i.e. the device is being destroyed. Drivers
+	 * using this callback are responsible for calling drm_dev_fini()
+	 * to finalize the device and then freeing the struct themselves.
+	 */
+	void (*release) (struct drm_device *);
+
 	int (*set_busid)(struct drm_device *dev, struct drm_master *master);
 
 	/**
@@ -437,6 +448,8 @@ 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);