fbdev/rivafb: 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>
Cc: Antonino Daplas <adaplas@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230927074722.6197-31-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -739,10 +739,11 @@ config FB_RIVA
 	tristate "nVidia Riva support"
 	depends on FB && PCI
 	select FB_BACKLIGHT if FB_RIVA_BACKLIGHT
-	select FB_MODE_HELPERS
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
+	select FB_IOMEM_FOPS
+	select FB_MODE_HELPERS
 	select BITREVERSE
 	select VGASTATE
 	select VIDEO_NOMODESET

drivers/video/fbdev/riva/fbdev.c

@@ -1670,6 +1670,7 @@ static const struct fb_ops riva_fb_ops = {
 	.owner 		= THIS_MODULE,
 	.fb_open	= rivafb_open,
 	.fb_release	= rivafb_release,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
 	.fb_check_var 	= rivafb_check_var,
 	.fb_set_par 	= rivafb_set_par,
 	.fb_setcolreg 	= rivafb_setcolreg,
@@ -1680,6 +1681,7 @@ static const struct fb_ops riva_fb_ops = {
 	.fb_imageblit 	= rivafb_imageblit,
 	.fb_cursor	= rivafb_cursor,
 	.fb_sync 	= rivafb_sync,
+	__FB_DEFAULT_IOMEM_OPS_MMAP,
 };
 
 static int riva_set_fbinfo(struct fb_info *info)