linux-kernel - Re: [PATCH] SOUND: Fix non-ISA_DMA

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Date:	Fri, 24 Jun 2011 12:16:08 +0100
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Jaroslav Kysela <perex@...ex.cz>, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
	linux-mips@...ux-mips.org
Subject: Re: [PATCH] SOUND: Fix non-ISA_DMA_API build failure

On Fri, Jun 24, 2011 at 10:26:13AM +0200, Takashi Iwai wrote:

> Hrm...  I still don't understand why ES18XX or others were selected at
> the first place.  Isn't it covered by the conditional in
> sound/isa/Kconfig like below?
> 
> ================================================================
> menuconfig SND_ISA
> 	bool "ISA sound devices"
> 	depends on ISA && ISA_DMA_API
> ...
> if SND_ISA
> ...
> config SND_ES18XX
> 	tristate "Generic ESS ES18xx driver"
> ...
> endif	# SND_ISA
> ================================================================
> 
> Isn't SND_ISA=n in your case although ISA_DMA_API=n?

The answer is hidden in this Kconfig warning:

warning: (RADIO_MIROPCM20) selects SND_ISA which has unmet direct dependencies (SOUND && !M68K && SND && ISA && ISA_DMA_API)

This is due to the following in drivers/media/radio/Kconfig:

config RADIO_MIROPCM20
        tristate "miroSOUND PCM20 radio"
        depends on ISA && VIDEO_V4L2 && SND
        select SND_ISA
        select SND_MIRO

So SND_ISA gets forced on even though the dependency on ISA_DMA_API is not
fulfilled.  That's solved by adding the dependency on ISA_DMA_API to
RADIO_MIROPCM20.

> Also, adlib driver is really only for ISA, so I see no big reason to
> allow this built for non-ISA.

With the patch applied:

[...]
menuconfig SND_ISA
        bool "ISA sound devices"
        depends on ISA
[...]

if SND_ISA

config SND_ADLIB
        tristate "AdLib FM card"
        select SND_OPL3_LIB
[...]

So the Adlib driver will still only be built with ISA enabled.  The only
thing that makes the Adlib driver different from all the others in the
ifdef SND_ISA ... endif bracket is that it does not directly or indirectly
use the ISA DMA API and that's in the end the reason why sound/isa/Kconfig
needs to be changed.

I originally approach this a different way but now that I'm explaining the
details I notice that it probably makes sense to split this patch into two:

 o The drivers/media/radio/Kconfig part should be applied for 3.0 and
   maybe -stable.
 o The sound/isa/Kconfig part is basically only fixing the dependency for
   the Adlib driver allowing it to be built on non-ISA_DMA_API system and
   is material for the next release after 3.0.

If you agree I'm going to repost the patch with aproprite log messages.

  Ralf
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