fbdev/amifb: 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/20230927074722.6197-5-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -225,6 +225,7 @@ config FB_Q40
 config FB_AMIGA
 	tristate "Amiga native chipset support"
 	depends on FB && AMIGA
+	select FB_IOMEM_FOPS
 	help
 	  This is the frame buffer device driver for the builtin graphics
 	  chipset found in Amigas.

drivers/video/fbdev/amifb.c

@@ -3488,6 +3488,7 @@ static irqreturn_t amifb_interrupt(int irq, void *dev_id)
 
 static const struct fb_ops amifb_ops = {
 	.owner		= THIS_MODULE,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
 	.fb_check_var	= amifb_check_var,
 	.fb_set_par	= amifb_set_par,
 	.fb_setcolreg	= amifb_setcolreg,
@@ -3497,6 +3498,7 @@ static const struct fb_ops amifb_ops = {
 	.fb_copyarea	= amifb_copyarea,
 	.fb_imageblit	= amifb_imageblit,
 	.fb_ioctl	= amifb_ioctl,
+	__FB_DEFAULT_IOMEM_OPS_MMAP,
 };