drm: Improve dumb callback docs

Noticed while reviewing a patch from Eric. Also add a todo for the
dumb_map_offset callbacks (it should be simple to do, but piles of
work). Plus fix up vbox, because vbox.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Nicholas Mc Guire <der.herr@hofr.at>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Fabio Rafael da Rosa <fdr@pid42.net>
Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181127091921.8325-1-daniel.vetter@ffwll.ch

3 files changed, 18 insertions, 3 deletions

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 9815b3b82bd1..ab347dec5079 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -28,6 +28,17 @@ them, but also all the virtual ones used by KVM, so everyone qualifies).
 
 Contact: Daniel Vetter, Thierry Reding, respective driver maintainers
 
+
+Remove custom dumb_map_offset implementations
+---------------------------------------------
+
+All GEM based drivers should be using drm_gem_create_mmap_offset() instead.
+Audit each individual driver, make sure it'll work with the generic
+implementation (there's lots of outdated locking leftovers in various
+implementations), and then remove it.
+
+Contact: Daniel Vetter, respective driver maintainers
+
 Convert existing KMS drivers to atomic modesetting
 --------------------------------------------------
 
diff --git a/drivers/staging/vboxvideo/vbox_drv.c b/drivers/staging/vboxvideo/vbox_drv.c
index 257030460fb6..d3e23dd70c1b 100644
--- a/drivers/staging/vboxvideo/vbox_drv.c
+++ b/drivers/staging/vboxvideo/vbox_drv.c
@@ -279,7 +279,6 @@ static struct drm_driver driver = {
         .gem_free_object_unlocked = vbox_gem_free_object,
         .dumb_create = vbox_dumb_create,
         .dumb_map_offset = vbox_dumb_mmap_offset,
-        .dumb_destroy = drm_gem_dumb_destroy,
         .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
         .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
         .gem_prime_export = drm_gem_prime_export,
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 252dd216cc60..35af23f5fa0d 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -527,8 +527,10 @@ struct drm_driver {
          * @dumb_map_offset:
          *
          * Allocate an offset in the drm device node's address space to be able to
-         * memory map a dumb buffer. GEM-based drivers must use
-         * drm_gem_create_mmap_offset() to implement this.
+         * memory map a dumb buffer.
+         *
+         * The default implementation is drm_gem_create_mmap_offset(). GEM based
+         * drivers must not overwrite this.
          *
          * Called by the user via ioctl.
          *
@@ -548,6 +550,9 @@ struct drm_driver {
          *
          * Called by the user via ioctl.
          *
+         * The default implementation is drm_gem_dumb_destroy(). GEM based drivers
+         * must not overwrite this.
+         *
          * Returns:
          *
          * Zero on success, negative errno on failure.