drm/gem-fb-helper: Add drm_gem_fb_create_with_dirty()

This adds a .fb_create helper that sets the .dirty callback to
drm_atomic_helper_dirtyfb().

v2: Improve docs (Daniel)

Signed-off-by: Noralf Trønnes <[e-mail]>
Acked-by: Daniel Vetter <[e-mail]>
Reviewed-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_gem_framebuffer_helper.c

···
 #include <drm/drmP.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_uapi.h>
+#include <drm/drm_damage_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
···
  * @mode_cmd: Metadata from the userspace framebuffer creation request
  * @funcs: vtable to be used for the new framebuffer object
  *
- * This can be used to set &drm_framebuffer_funcs for drivers that need the
- * &drm_framebuffer_funcs.dirty callback. Use drm_gem_fb_create() if you don't
- * need to change &drm_framebuffer_funcs.
- * The function does buffer size validation.
+ * This function can be used to set &drm_framebuffer_funcs for drivers that need
+ * custom framebuffer callbacks. Use drm_gem_fb_create() if you don't need to
+ * change &drm_framebuffer_funcs. The function does buffer size validation.
  *
  * Returns:
  * Pointer to a &drm_framebuffer on success or an error pointer on failure.
···
  *
  * If your hardware has special alignment or pitch requirements these should be
  * checked before calling this function. The function does buffer size
- * validation. Use drm_gem_fb_create_with_funcs() if you need to set
- * &drm_framebuffer_funcs.dirty.
+ * validation. Use drm_gem_fb_create_with_dirty() if you need framebuffer
+ * flushing.
  *
  * Drivers can use this as their &drm_mode_config_funcs.fb_create callback.
  * The ADDFB2 IOCTL calls into this callback.
···
 					    &drm_gem_fb_funcs);
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_create);
+
+static const struct drm_framebuffer_funcs drm_gem_fb_funcs_dirtyfb = {
+	.destroy	= drm_gem_fb_destroy,
+	.create_handle	= drm_gem_fb_create_handle,
+	.dirty		= drm_atomic_helper_dirtyfb,
+};
+
+/**
+ * drm_gem_fb_create_with_dirty() - Helper function for the
+ *                       &drm_mode_config_funcs.fb_create callback
+ * @dev: DRM device
+ * @file: DRM file that holds the GEM handle(s) backing the framebuffer
+ * @mode_cmd: Metadata from the userspace framebuffer creation request
+ *
+ * This function creates a new framebuffer object described by
+ * &drm_mode_fb_cmd2. This description includes handles for the buffer(s)
+ * backing the framebuffer. drm_atomic_helper_dirtyfb() is used for the dirty
+ * callback giving framebuffer flushing through the atomic machinery. Use
+ * drm_gem_fb_create() if you don't need the dirty callback.
+ * The function does buffer size validation.
+ *
+ * Drivers should also call drm_plane_enable_fb_damage_clips() on all planes
+ * to enable userspace to use damage clips also with the ATOMIC IOCTL.
+ *
+ * Drivers can use this as their &drm_mode_config_funcs.fb_create callback.
+ * The ADDFB2 IOCTL calls into this callback.
+ *
+ * Returns:
+ * Pointer to a &drm_framebuffer on success or an error pointer on failure.
+ */
+struct drm_framebuffer *
+drm_gem_fb_create_with_dirty(struct drm_device *dev, struct drm_file *file,
+			     const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
+					    &drm_gem_fb_funcs_dirtyfb);
+}
+EXPORT_SYMBOL_GPL(drm_gem_fb_create_with_dirty);
 
 /**
  * drm_gem_fb_prepare_fb() - Prepare a GEM backed framebuffer

include/drm/drm_gem_framebuffer_helper.h

···
 struct drm_framebuffer *
 drm_gem_fb_create(struct drm_device *dev, struct drm_file *file,
 		  const struct drm_mode_fb_cmd2 *mode_cmd);
+struct drm_framebuffer *
+drm_gem_fb_create_with_dirty(struct drm_device *dev, struct drm_file *file,
+			     const struct drm_mode_fb_cmd2 *mode_cmd);
 
 int drm_gem_fb_prepare_fb(struct drm_plane *plane,
 			  struct drm_plane_state *state);