fbdev: fb_defio not buildable as module

Hi *,

in drivers/video/fbdev/Kconfig we have

| menuconfig FB
|        tristate "Support for frame buffer devices"
|        select FB_CMDLINE
|        ---help---

and

| config FB_DEFERRED_IO
|        bool
|        depends on FB

but in drivers/video/fbdev/core/Makefile we have the line
| obj-$(CONFIG_FB_DEFERRED_IO)   += fb_defio.o

AFAICS the combination of this leads to fb_defio always
linked into the kernel image, even if the framebuffer core
is only built as a module. This doesn't make much sense and
I couldn't find any reason why this would be necessary.

The above code is there in one way or the other since the
initial version of fb_defio.c - I wonder what was the
intended behaviour or actually what is considered the right
way today?

TIA,
Harald