From mboxrd@z Thu Jan  1 00:00:00 1970
From: Clemens Ladisch <clemens@ladisch.de>
Subject: Re: Why use spin_lock or spin_lock_irq in trigger
 callback (audio capture)?
Date: Fri, 26 Feb 2010 10:05:43 +0100
Message-ID: <4B878EE7.2010200@ladisch.de>
References: <e5baf3861002251332n7333fb12tb15b055baffaa4a2@mail.gmail.com>
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To: Yiliang Bao <yiliangb@gmail.com>
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Yiliang Bao wrote:
> I looked at some PCI audio capture driver like BT878 (sound/pci/bt87x.c) or
> SAA7134 (drivers/media/video/saa7134-alsa.c), I found that spin_lock instead
> of spin_lock_irq (or spin_lock_irqsave) is used in trigger function. Is
> there any reason for that?

Yes, the trigger callback is called with interrupts already disabled.
http://www.alsa-project.org/~tiwai/writing-an-alsa-driver/ch05s08.html


Regards,
Clemens