Atomic operators in alsa driver

Atomic operators in alsa driver

[Eliot Blennerhassett]

A question to clarify which 'operators' are atomic i.e. inside spinlock.

As far as I can make out from Takashi's Writing an Alsa driver, Chapter 5,
section "Operators" (am I correct?)

Atomic:
trigger callback
pointer callback

Non-atomic:
open callback
close callback
ioctl callback
hw_params callback
hw_free callback
prepare callback
copy and silence callbacks
ack callback
page callback

This could be clarified explicitly in the section "Atomicity"

thanks

Eliot


Eliot Blennerhassett
AudioScience Inc.
--
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Re: Atomic operators in alsa driver

[Jaroslav Kysela]

On Tue, 10 Aug 2004, Eliot Blennerhassett wrote:

> A question to clarify which 'operators' are atomic i.e. inside spinlock.
> 
> As far as I can make out from Takashi's Writing an Alsa driver, Chapter 5,
> section "Operators" (am I correct?)
> 
> Atomic:
> trigger callback
> pointer callback
> 
> Non-atomic:
> open callback
> close callback
> ioctl callback
> hw_params callback
> hw_free callback
> prepare callback
> copy and silence callbacks
> ack callback
> page callback

It's correct.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs


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Re: Atomic operators in alsa driver

[Takashi Iwai]

At Wed, 11 Aug 2004 15:19:20 +0200 (CEST),
Jaroslav wrote:
> 
> On Tue, 10 Aug 2004, Eliot Blennerhassett wrote:
> 
> > A question to clarify which 'operators' are atomic i.e. inside spinlock.
> > 
> > As far as I can make out from Takashi's Writing an Alsa driver, Chapter 5,
> > section "Operators" (am I correct?)
> > 
> > Atomic:
> > trigger callback
> > pointer callback
> > 
> > Non-atomic:
> > open callback
> > close callback
> > ioctl callback
> > hw_params callback
> > hw_free callback
> > prepare callback
> > copy and silence callbacks
> > ack callback
> > page callback
> 
> It's correct.

In practice, ack callback is usually treated as atomic to get finer
processing of data transfer.  For example, ack is called in the
pointer callback in pcm-indirect.h.  But basically it can be
non-atomic, too.


Takashi


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