drm: use anon-inode instead of relying on cdevs

DRM drivers share a common address_space across all character-devices of a
single DRM device. This allows simple buffer eviction and mapping-control.
However, DRM core currently waits for the first ->open() on any char-dev
to mark the underlying inode as backing inode of the device. This delayed
initialization causes ugly conditions all over the place:
  if (dev->dev_mapping)
    do_sth();

To avoid delayed initialization and to stop reusing the inode of the
char-dev, we allocate an anonymous inode for each DRM device and reset
filp->f_mapping to it on ->open().

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 04a7f31301f8..3227b716ffdf 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1183,7 +1183,7 @@ struct drm_device {
         struct drm_sg_mem *sg;  /**< Scatter gather memory */
         unsigned int num_crtcs;                  /**< Number of CRTCs on this device */
         void *dev_private;              /**< device private data */
-        struct address_space *dev_mapping;
+        struct inode *anon_inode;
         struct drm_sigdata sigdata;        /**< For block_all_signals */
         sigset_t sigmask;