linux-kernel - Re: Using IO functions across ARM, PPC and Microblaze architectures

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Message-ID: <CAMuHMdVNszTFRjqiUoZ42+noaOcGjLZyZ9O30c5UVNNJhp0LMw@mail.gmail.com>
Date:	Sat, 8 Dec 2012 11:57:39 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Michal Simek <monstr@...str.eu>, linux-arch@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	David Hinds <dahinds@...rs.sourceforge.net>
Subject: Re: Using IO functions across ARM, PPC and Microblaze architectures

On Fri, Dec 7, 2012 at 10:16 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>> Because I need to use IO functions which will behave
>> on arm as little endian and on powerpc as big endian
>> and on microblaze depends on endian setting.
>> I haven't found any IO function which I could use by 3 architectures
>> without using preprocessor macros or runtime detection
>
> Its a rather weird mix. We can do "always big" and "always little"
>
>> 1. Using helper function + preprocessor macros
>> (using static inline function also possible)
>
> Then someone comes along and sticks a daughterboard into the system with
> the same device the other way around and there are years
>
>> 2. Using function pointers
>
> Probably smarter. 8250.c works this way and it has to handle some
> extremely bizarre mappings.
>
>> b) Runtime initialization - here is the question if there is
>> any standard function which I could use.
>
> Set the pointers up and pass them as data with your platform device, that
> way the function definitions are buried in your platform code where they
> depend.

Or embed a struct io_ops * in struct device, to be set up by the bus driver?

Wasn't David Hinds working on something like this in the context of PCMCIA
a few decades ago?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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
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