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, 17 insertions, 17 deletions

diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index 5aec3e81fe24..c8d972763889 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -153,24 +153,24 @@ static struct {
 static void evict_entry(struct drm_gem_object *obj,
                 enum tiler_fmt fmt, struct usergart_entry *entry)
 {
-        if (obj->dev->dev_mapping) {
-                struct omap_gem_object *omap_obj = to_omap_bo(obj);
-                int n = usergart[fmt].height;
-                size_t size = PAGE_SIZE * n;
-                loff_t off = mmap_offset(obj) +
-                                (entry->obj_pgoff << PAGE_SHIFT);
-                const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
-                if (m > 1) {
-                        int i;
-                        /* if stride > than PAGE_SIZE then sparse mapping: */
-                        for (i = n; i > 0; i--) {
-                                unmap_mapping_range(obj->dev->dev_mapping,
-                                                off, PAGE_SIZE, 1);
-                                off += PAGE_SIZE * m;
-                        }
-                } else {
-                        unmap_mapping_range(obj->dev->dev_mapping, off, size, 1);
+        struct omap_gem_object *omap_obj = to_omap_bo(obj);
+        int n = usergart[fmt].height;
+        size_t size = PAGE_SIZE * n;
+        loff_t off = mmap_offset(obj) +
+                        (entry->obj_pgoff << PAGE_SHIFT);
+        const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
+
+        if (m > 1) {
+                int i;
+                /* if stride > than PAGE_SIZE then sparse mapping: */
+                for (i = n; i > 0; i--) {
+                        unmap_mapping_range(obj->dev->anon_inode->i_mapping,
+                                            off, PAGE_SIZE, 1);
+                        off += PAGE_SIZE * m;
                 }
+        } else {
+                unmap_mapping_range(obj->dev->anon_inode->i_mapping,
+                                    off, size, 1);
         }
 
         entry->obj = NULL;