linux-kernel - Re: [Device-drivers-devel] [PATCH] Add driver for Analog Devices ADAU1701 SigmaDSP

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Message-ID: <20110419080629.GA16357@opensource.wolfsonmicro.com>
Date:	Tue, 19 Apr 2011 09:06:29 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Andres Salomon <dilinger@...ued.net>
Cc:	cliff.cai@...log.com, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org,
	device-drivers-devel@...ckfin.uclinux.org,
	akpm@...ux-foundation.org, lrg@...mlogic.co.uk,
	Mike Frysinger <vapier.adi@...il.com>
Subject: Re: [Device-drivers-devel] [PATCH] Add driver for Analog Devices
 ADAU1701 SigmaDSP

On Mon, Apr 18, 2011 at 05:15:05PM -0700, Andres Salomon wrote:
> Mark Brown <broonie@...nsource.wolfsonmicro.com> wrote:

> > Given the number of people looking at this from various angles I'd
> > expect to see some sort of progress this year (probably in the next
> > quater or so), but obviously no guarantees.

> Out of curiosity, has any progress been made on this?

No, it's only been a month.

> What would actually cause the firmware to change?  Would the userspace
> application that's currently driving the codec know that it needs to
> load a new firmware, or will there be multiple applications potentially
> interacting with the codec (with only one driving it, and another
> deciding that the firmware should change)?

Clearly something in userspace will need to be able to do this.

> One can imagine two different types of APIs depending upon the answers
> to those questions.  If the application driving the codec is also
> changing the firmware, a simple 'echo new_firmware_name.bin >
> /sys/.../filter_coeff' (or equivalent ALSA function)

Using sysfs isn't going to fly for all the reasons discussed upthread -
it's not enumerable and it's not going to cope with large coefficient
sets.

> However, if multiple applications are going to be interacting with
> the codec, I'd imagine we'd need something more complex; perhaps a hook
> in snd_soc_dai_ops that's called anytime stream state changes?  That

Using the ops isn't going to work as there's no reason a coefficient set
has to be associated with a DAI.
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