From: Rene Herman <rene.herman@keyaccess.nl>
To: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Takashi Iwai <tiwai@suse.de>, Alsa-devel <alsa-devel@alsa-project.org>
Subject: Re: [PATCH] wss_lib: do not mess mixer settings during probe
Date: Mon, 25 Aug 2008 00:37:52 +0200 [thread overview]
Message-ID: <48B1E2C0.8000105@keyaccess.nl> (raw)
In-Reply-To: <20080824214832.daa13d68.krzysztof.h1@poczta.fm>
On 24-08-08 21:48, Krzysztof Helt wrote:
>From the Documentation/memory-barriers.txt
> "
> (*) inX(), outX():
> ...
> They are guaranteed to be fully ordered with respect to each other.
>
> They are not guaranteed to be fully ordered with respect to other types of
> memory and I/O operation.
> ...
> "
>
> No barriers are needed in this case.
On x86 certainly not and I would expect these barriers are there for
cases/architectures where inb() and outb() are redefined to memory
mapped I/O or there would just be no point at all.
In that case, the first outb() writes an index and we'd better make sure
that it hits the hardware before we write the value. Hence my suspicion
that if at all, the mb() should be in between.
No idea who added those and why...
Rene
next prev parent reply other threads:[~2008-08-24 22:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-24 16:08 [PATCH] wss_lib: do not mess mixer settings during probe Krzysztof Helt
2008-08-24 18:36 ` Rene Herman
2008-08-24 19:48 ` Krzysztof Helt
2008-08-24 22:37 ` Rene Herman [this message]
2008-08-25 0:23 ` Rene Herman
2008-08-25 5:45 ` Takashi Iwai
2008-08-25 6:19 ` Takashi Iwai
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