linux-kernel - Re: [PATCH] include/asm-generic/io.h: add 'UML' case just like 'no-MMU'

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Message-ID: <CAMuHMdXw6VYhnNWcVfWc9ssxKTqKFcDbN4WXL5i=eNGy+gXcRA@mail.gmail.com>
Date:	Wed, 26 Jun 2013 11:48:20 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Richard Weinberger <richard@....at>
Cc:	Chen Gang <gang.chen@...anux.com>, Jeff Dike <jdike@...toit.com>,
	Arnd Bergmann <arnd@...db.de>,
	David Sharp <dhsharp@...gle.com>,
	"sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>,
	uml-user <user-mode-linux-user@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] include/asm-generic/io.h: add 'UML' case just like 'no-MMU'

On Wed, Jun 26, 2013 at 11:38 AM, Richard Weinberger <richard@....at> wrote:
>> 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.

>> 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@...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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