drm: add prime helpers

Instead of reimplementing all of the dma_buf functionality in every driver,
create helpers drm_prime_import and drm_prime_export that implement them in
terms of new, lower-level hook functions:

  gem_prime_pin: callback when a buffer is created, used to pin buffers into GTT
  gem_prime_get_sg_table: convert a drm_gem_object to an sg_table for export
  gem_prime_import_sg_table: convert an sg_table into a drm_gem_object
  gem_prime_vmap, gem_prime_vunmap: map and unmap an object

These hooks are optional; drivers can opt in by using drm_gem_prime_import and
drm_gem_prime_export as the .gem_prime_import and .gem_prime_export fields of
struct drm_driver.

v2:
- Drop .begin_cpu_access.  None of the drivers this code replaces implemented
  it.  Having it here was a leftover from when I was trying to include i915 in
  this rework.
- Use mutex_lock instead of mutex_lock_interruptible, as these three drivers
  did.  This patch series shouldn't change that behavior.
- Rename helpers to gem_prime_get_sg_table and gem_prime_import_sg_table.
  Rename struct sg_table* variables to 'sgt' for clarity.
- Update drm.tmpl for these new hooks.

v3:
- Pass the vaddr down to the driver.  This lets drivers that just call vunmap on
  the pointer avoid having to store the pointer in their GEM private structures.
- Move documentation into a /** DOC */ comment in drm_prime.c and include it in
  drm.tmpl with a !P line.  I tried to use !F lines to include documentation of
  the individual functions from drmP.h, but the docproc / kernel-doc scripts
  barf on that file, so hopefully this is good enough for now.
- apply refcount fix from commit be8a42ae60addd8b6092535c11b42d099d6470ec
  ("drm/prime: drop reference on imported dma-buf come from gem")

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 3aaa50d64451..2d94d7413d71 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -930,6 +930,14 @@ struct drm_driver {
         /* import dmabuf -> GEM */
         struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
                                 struct dma_buf *dma_buf);
+        /* low-level interface used by drm_gem_prime_{import,export} */
+        int (*gem_prime_pin)(struct drm_gem_object *obj);
+        struct sg_table *(*gem_prime_get_sg_table)(struct drm_gem_object *obj);
+        struct drm_gem_object *(*gem_prime_import_sg_table)(
+                                struct drm_device *dev, size_t size,
+                                struct sg_table *sgt);
+        void *(*gem_prime_vmap)(struct drm_gem_object *obj);
+        void (*gem_prime_vunmap)(struct drm_gem_object *obj, void *vaddr);
 
         /* vga arb irq handler */
         void (*vgaarb_irq)(struct drm_device *dev, bool state);
@@ -1562,9 +1570,13 @@ extern int drm_clients_info(struct seq_file *m, void* data);
 extern int drm_gem_name_info(struct seq_file *m, void *data);
 
 
+extern struct dma_buf *drm_gem_prime_export(struct drm_device *dev,
+                struct drm_gem_object *obj, int flags);
 extern int drm_gem_prime_handle_to_fd(struct drm_device *dev,
                 struct drm_file *file_priv, uint32_t handle, uint32_t flags,
                 int *prime_fd);
+extern struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
+                struct dma_buf *dma_buf);
 extern int drm_gem_prime_fd_to_handle(struct drm_device *dev,
                 struct drm_file *file_priv, int prime_fd, uint32_t *handle);