drm/fb-cma-helper: Add fb_deferred_io support

This adds fbdev deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
The driver has to provide a (struct drm_framebuffer_funcs *)->dirty()
callback to get notification of fbdev framebuffer changes.
If the dirty() hook is set, then fb_deferred_io is set up automatically
by the helper.

Two functions have been added so that the driver can provide a dirty()
function:
- drm_fbdev_cma_init_with_funcs()
  This makes it possible for the driver to provided a custom
  (struct drm_fb_helper_funcs *)->fb_probe() function.
- drm_fbdev_cma_create_with_funcs()
  This is used by the .fb_probe hook to set a driver provided
  (struct drm_framebuffer_funcs *)->dirty() function.

Cc: laurent.pinchart@ideasonboard.com
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1461856717-6476-6-git-send-email-noralf@tronnes.org

include/drm/drm_fb_cma_helper.h

@@ -4,11 +4,18 @@
 struct drm_fbdev_cma;
 struct drm_gem_cma_object;
 
+struct drm_fb_helper_surface_size;
+struct drm_framebuffer_funcs;
+struct drm_fb_helper_funcs;
 struct drm_framebuffer;
+struct drm_fb_helper;
 struct drm_device;
 struct drm_file;
 struct drm_mode_fb_cmd2;
 
+struct drm_fbdev_cma *drm_fbdev_cma_init_with_funcs(struct drm_device *dev,
+	unsigned int preferred_bpp, unsigned int num_crtc,
+	unsigned int max_conn_count, const struct drm_fb_helper_funcs *funcs);
 struct drm_fbdev_cma *drm_fbdev_cma_init(struct drm_device *dev,
 	unsigned int preferred_bpp, unsigned int num_crtc,
 	unsigned int max_conn_count);
@@ -16,6 +23,13 @@ void drm_fbdev_cma_fini(struct drm_fbdev_cma *fbdev_cma);
 
 void drm_fbdev_cma_restore_mode(struct drm_fbdev_cma *fbdev_cma);
 void drm_fbdev_cma_hotplug_event(struct drm_fbdev_cma *fbdev_cma);
+int drm_fbdev_cma_create_with_funcs(struct drm_fb_helper *helper,
+	struct drm_fb_helper_surface_size *sizes,
+	struct drm_framebuffer_funcs *funcs);
+
+void drm_fb_cma_destroy(struct drm_framebuffer *fb);
+int drm_fb_cma_create_handle(struct drm_framebuffer *fb,
+	struct drm_file *file_priv, unsigned int *handle);
 
 struct drm_framebuffer *drm_fb_cma_create(struct drm_device *dev,
 	struct drm_file *file_priv, const struct drm_mode_fb_cmd2 *mode_cmd);