On Wed, Jun 26, 2013 at 11:38 AM, Richard Weinberger [off-list ref] wrote:

quoted

Since the API itself already contents the meaning: "return NULL means
the arch has no related io memory",

No, NULL means it could not map the I/O memory.

quoted

Why not define a generic dummy one in "include/asm-generic/io.h" instead
of "HAS_IOMEM" (which has already spread many various places, and also,
most of new drivers have to know about it).

e.g: in "include/asm-generic/io.h", if "CONFIG_HAS_IOMEM=n", define a
dummy ioremap() which return NULL ... (also need consider more details).

Because we don't even want to build these drivers and not make them fail while
executing io memory related functions.

Indeed, it doesn't make sense to build drivers that cannot work.
And they may fail in a very bad way.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds