drm/msm: Use regular fbdev I/O helpers

Use the regular fbdev helpers for framebuffer I/O instead of DRM's
helpers. Msm does not use damage handling, so DRM's fbdev helpers
are mere wrappers around the fbdev code.

By using fbdev helpers directly within each DRM fbdev emulation,
we can eventually remove DRM's wrapper functions entirely.

Msm's fbdev emulation has been incomplete as it didn't implement
damage handling. Partilly fix this by implementing damage handling
for write and draw operation. It is still missing for mmaped pages.

v4:
	* use initializer macros for struct fb_ops
	* partially support damage handling
v2:
	* use FB_SYS_HELPERS option
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Sean Paul <sean@poorly.run>
Link: https://patchwork.freedesktop.org/patch/msgid/20230530151228.22979-12-tzimmermann@suse.de

drivers/gpu/drm/msm/Kconfig

@@ -21,6 +21,7 @@ config DRM_MSM
 	select DRM_BRIDGE
 	select DRM_PANEL_BRIDGE
 	select DRM_SCHED
+	select FB_SYS_HELPERS if DRM_FBDEV_EMULATION
 	select SHMEM
 	select TMPFS
 	select QCOM_SCM

drivers/gpu/drm/msm/msm_fbdev.c

@@ -4,6 +4,8 @@
  * Author: Rob Clark <robdclark@gmail.com>
  */
 
+#include <linux/fb.h>
+
 #include <drm/drm_drv.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_fb_helper.h>
@@ -23,6 +25,10 @@ module_param(fbdev, bool, 0600);
  * fbdev funcs, to implement legacy fbdev interface on top of drm driver
  */
 
+FB_GEN_DEFAULT_DEFERRED_SYS_OPS(msm_fbdev,
+				drm_fb_helper_damage_range,
+				drm_fb_helper_damage_area)
+
 static int msm_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
 	struct drm_fb_helper *helper = (struct drm_fb_helper *)info->par;
@@ -52,16 +58,9 @@ static void msm_fbdev_fb_destroy(struct fb_info *info)
 
 static const struct fb_ops msm_fb_ops = {
 	.owner = THIS_MODULE,
+	__FB_DEFAULT_DEFERRED_OPS_RDWR(msm_fbdev),
 	DRM_FB_HELPER_DEFAULT_OPS,
-
-	/* Note: to properly handle manual update displays, we wrap the
-	 * basic fbdev ops which write to the framebuffer
-	 */
-	.fb_read = drm_fb_helper_sys_read,
-	.fb_write = drm_fb_helper_sys_write,
-	.fb_fillrect = drm_fb_helper_sys_fillrect,
-	.fb_copyarea = drm_fb_helper_sys_copyarea,
-	.fb_imageblit = drm_fb_helper_sys_imageblit,
+	__FB_DEFAULT_DEFERRED_OPS_DRAW(msm_fbdev),
 	.fb_mmap = msm_fbdev_mmap,
 	.fb_destroy = msm_fbdev_fb_destroy,
 };