drm: GEM mmap support

Add core support for mapping of GEM objects.  Drivers should provide a
vm_operations_struct if they want to support page faulting of objects.
The code for handling GEM object offsets was taken from TTM, which was
written by Thomas Hellström.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index f2285237df49..3a6c439652a5 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -133,11 +133,21 @@ int drm_open(struct inode *inode, struct file *filp)
                 spin_lock(&dev->count_lock);
                 if (!dev->open_count++) {
                         spin_unlock(&dev->count_lock);
-                        return drm_setup(dev);
+                        retcode = drm_setup(dev);
+                        goto out;
                 }
                 spin_unlock(&dev->count_lock);
         }
 
+out:
+        mutex_lock(&dev->struct_mutex);
+        if (dev->dev_mapping == NULL)
+                dev->dev_mapping = inode->i_mapping;
+        else if (dev->dev_mapping != inode->i_mapping)
+                WARN(1, "dev->dev_mapping not inode mapping (%p expected %p)\n",
+                     dev->dev_mapping, inode->i_mapping);
+        mutex_unlock(&dev->struct_mutex);
+
         return retcode;
 }
 EXPORT_SYMBOL(drm_open);