fbdev/gbefb: Initialize fb_ops to fbdev I/O-memory helpers

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

Fbdev drivers sometimes rely on the callbacks being NULL for a
default 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.

No functional changes.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230927074722.6197-16-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -498,9 +498,7 @@ config FB_GBE
 	bool "SGI Graphics Backend frame buffer support"
 	depends on (FB = y) && HAS_IOMEM
 	depends on SGI_IP32 || COMPILE_TEST
-	select FB_CFB_FILLRECT
-	select FB_CFB_COPYAREA
-	select FB_CFB_IMAGEBLIT
+	select FB_IOMEM_HELPERS
 	help
 	  This is the frame buffer device driver for SGI Graphics Backend.
 	  This chip is used in SGI O2 and Visual Workstation 320/540.

drivers/video/fbdev/gbefb.c

@@ -1044,14 +1044,13 @@ static int gbefb_mmap(struct fb_info *info,
 
 static const struct fb_ops gbefb_ops = {
 	.owner		= THIS_MODULE,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
 	.fb_check_var	= gbefb_check_var,
 	.fb_set_par	= gbefb_set_par,
 	.fb_setcolreg	= gbefb_setcolreg,
-	.fb_mmap	= gbefb_mmap,
 	.fb_blank	= gbefb_blank,
-	.fb_fillrect	= cfb_fillrect,
-	.fb_copyarea	= cfb_copyarea,
-	.fb_imageblit	= cfb_imageblit,
+	__FB_DEFAULT_IOMEM_OPS_DRAW,
+	.fb_mmap	= gbefb_mmap,
 };
 
 /*