fbdev/vfb: Initialize fb_ops with fbdev macros

Initialize the instance of struct fb_ops with fbdev initializer
macros for framebuffers in virtual address space. Set the read/write,
draw and mmap callbacks to the correct implementation and avoid
implicit defaults. Also select the necessary helpers in Kconfig.

Fbdev drivers sometimes rely on the callbacks being NULL for a
default I/O-memory-based implementation to be invoked; hence
requiring the I/O helpers to be built in any case. Setting all
callbacks in all drivers explicitly will allow to make the I/O
helpers optional. This benefits systems that do not use these
functions.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231127131655.4020-5-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -1800,10 +1800,7 @@ config FB_DA8XX
 config FB_VIRTUAL
 	tristate "Virtual Frame Buffer support (ONLY FOR TESTING!)"
 	depends on FB
-	select FB_SYS_FILLRECT
-	select FB_SYS_COPYAREA
-	select FB_SYS_IMAGEBLIT
-	select FB_SYS_FOPS
+	select FB_SYSMEM_HELPERS
 	help
 	  This is a `virtual' frame buffer device. It operates on a chunk of
 	  unswappable kernel memory instead of on the memory of a graphics

drivers/video/fbdev/vfb.c

@@ -80,15 +80,12 @@ static int vfb_mmap(struct fb_info *info,
 
 static const struct fb_ops vfb_ops = {
 	.owner		= THIS_MODULE,
-	.fb_read        = fb_sys_read,
-	.fb_write       = fb_sys_write,
+	__FB_DEFAULT_SYSMEM_OPS_RDWR,
 	.fb_check_var	= vfb_check_var,
 	.fb_set_par	= vfb_set_par,
 	.fb_setcolreg	= vfb_setcolreg,
 	.fb_pan_display	= vfb_pan_display,
-	.fb_fillrect	= sys_fillrect,
-	.fb_copyarea	= sys_copyarea,
-	.fb_imageblit	= sys_imageblit,
+	__FB_DEFAULT_SYSMEM_OPS_DRAW,
 	.fb_mmap	= vfb_mmap,
 };