fbdev/intelfb: 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: Maik Broemme <mbroemme@libmpq.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230927074722.6197-22-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -861,10 +861,11 @@ config FB_CARILLO_RANCH
 config FB_INTEL
 	tristate "Intel 830M/845G/852GM/855GM/865G/915G/945G/945GM/965G/965GM support"
 	depends on FB && PCI && X86 && AGP_INTEL && EXPERT
-	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 BOOT_VESA_SUPPORT if FB_INTEL = y
 	select VIDEO_NOMODESET
 	depends on !DRM_I915

drivers/video/fbdev/intelfb/intelfbdrv.c

@@ -198,6 +198,7 @@ static const struct fb_ops intel_fb_ops = {
 	.owner =		THIS_MODULE,
 	.fb_open =              intelfb_open,
 	.fb_release =           intelfb_release,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
 	.fb_check_var =         intelfb_check_var,
 	.fb_set_par =           intelfb_set_par,
 	.fb_setcolreg =		intelfb_setcolreg,
@@ -208,7 +209,8 @@ static const struct fb_ops intel_fb_ops = {
 	.fb_imageblit =         intelfb_imageblit,
 	.fb_cursor =            intelfb_cursor,
 	.fb_sync =              intelfb_sync,
-	.fb_ioctl =		intelfb_ioctl
+	.fb_ioctl =		intelfb_ioctl,
+	__FB_DEFAULT_IOMEM_OPS_MMAP,
 };
 
 /* PCI driver module table */