fbdev: Provide I/O-memory helpers as module

Provide helpers for accessing I/O memory in a helper module. The fbdev
core uses these helpers, so select the module unconditionally for fbdev.
Drivers will later be able to select the module individually and the
helpers will become optional.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230927074722.6197-2-tzimmermann@suse.de

drivers/video/fbdev/core/Kconfig

@@ -4,6 +4,7 @@
 #
 
 config FB_CORE
+	select FB_IOMEM_FOPS
 	select VIDEO_CMDLINE
 	tristate
 
@@ -144,12 +145,17 @@ config FB_DMAMEM_HELPERS
 	select FB_SYS_FOPS
 	select FB_SYS_IMAGEBLIT
 
+config FB_IOMEM_FOPS
+	tristate
+	depends on FB_CORE
+
 config FB_IOMEM_HELPERS
 	bool
 	depends on FB_CORE
 	select FB_CFB_COPYAREA
 	select FB_CFB_FILLRECT
 	select FB_CFB_IMAGEBLIT
+	select FB_IOMEM_FOPS
 
 config FB_IOMEM_HELPERS_DEFERRED
 	bool

drivers/video/fbdev/core/Makefile

@@ -3,7 +3,7 @@ obj-$(CONFIG_FB_NOTIFY)           += fb_notify.o
 obj-$(CONFIG_FB_CORE)             += fb.o
 fb-y                              := fb_info.o \
                                      fbmem.o fbcmap.o \
-                                     modedb.o fbcvt.o fb_cmdline.o fb_io_fops.o
+                                     modedb.o fbcvt.o fb_cmdline.o
 ifdef CONFIG_FB
 fb-y                              += fb_backlight.o fbmon.o
 endif
@@ -28,6 +28,7 @@ fb-$(CONFIG_LOGO)		  += fb_logo.o
 obj-$(CONFIG_FB_CFB_FILLRECT)  += cfbfillrect.o
 obj-$(CONFIG_FB_CFB_COPYAREA)  += cfbcopyarea.o
 obj-$(CONFIG_FB_CFB_IMAGEBLIT) += cfbimgblt.o
+obj-$(CONFIG_FB_IOMEM_FOPS)    += fb_io_fops.o
 obj-$(CONFIG_FB_SYS_FILLRECT)  += sysfillrect.o
 obj-$(CONFIG_FB_SYS_COPYAREA)  += syscopyarea.o
 obj-$(CONFIG_FB_SYS_IMAGEBLIT) += sysimgblt.o

drivers/video/fbdev/core/fb_io_fops.c

@@ -131,3 +131,6 @@ ssize_t fb_io_write(struct fb_info *info, const char __user *buf, size_t count,
 	return (cnt) ? cnt : err;
 }
 EXPORT_SYMBOL(fb_io_write);
+
+MODULE_DESCRIPTION("Fbdev helpers for framebuffers in I/O memory");
+MODULE_LICENSE("GPL");