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Re: mips allmodconfig

To: Takashi Iwai <tiwai@suse.de>
Subject: Re: mips allmodconfig
From: Ralf Baechle <ralf@linux-mips.org>
Date: Sun, 30 Jan 2011 17:04:44 +0100
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mips@linux-mips.org
In-reply-to: <s5hfwsdcwht.wl%tiwai@suse.de>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20110125143113.55aea198.akpm@linux-foundation.org> <s5hfwsdcwht.wl%tiwai@suse.de>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.21 (2010-09-15)
On Fri, Jan 28, 2011 at 08:34:22AM +0100, Takashi Iwai wrote:

> > sound/oss/soundcard.c:69: error: `MAX_DMA_CHANNELS' undeclared here (not in 
> > a function)
> > sound/oss/soundcard.c:69: error: storage size of `dma_alloc_map' isn't known
> > sound/oss/soundcard.c:69: warning: 'dma_alloc_map' defined but not used     
> >     
> > 
> > In case you happen to be interested in oss drivers ;)
> 
> I took a quick look.  The only case where no MAX_DMA_CHANNELS is
> defined is only MIPS with CONFIG_GENERIC_ISA_DMA_SUPPORT_BROKEN.
> In arch/mips/include/asm/dma.h:
> 
> #ifndef CONFIG_GENERIC_ISA_DMA_SUPPORT_BROKEN
> #define MAX_DMA_CHANNELS      8
> #endif
> 
> What is the intention of this ifdef?

Uh...  It's a while, took a little headscratching until I remembered
again and I think the comment of aa414dff4f7bef29457592414551becdca72dd6b
is bogus ...

CONFIG_GENERIC_ISA_DMA enabled but MAX_DMA_CHANNELS disabled selects a
dummy version of the ISA DMA controller API.  Some drivers don't have
correct dependencies or ifdefs on CONFIG_GENERIC_ISA_DMA or don't
have correct fallback strategies in case of CONFIG_GENERIC_ISA_DMA=n.
In those cases just leaving MAX_DMA_CHANNELS undefined is useful.  This
is used on SGI Indigo² systems which have EISA slots but ISA DMA isn't
supported yet by Linux.

> Takashi  (not interested but just bored ;)

Very interested boredom ;-)

  Ralf

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