linux-kernel - Re: [PATCH 1/2] ASoC: tfa9879: New driver for NXP Semiconductors TFA9879 amplifier.

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Message-ID: <20141106160241.GM8509@sirena.org.uk>
Date:	Thu, 6 Nov 2014 16:02:41 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Peter Rosin <peda@...ntia.se>
Cc:	Peter Rosin <peda@...ator.liu.se>,
	Lars-Peter Clausen <lars@...afoo.de>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] ASoC: tfa9879: New driver for NXP Semiconductors
 TFA9879 amplifier.

On Thu, Nov 06, 2014 at 02:37:31PM +0000, Peter Rosin wrote:
> Mark Brown wrote:

> > > +	if (tfa9879->lsb_justified)
> > > +		TFA9879_REG(codec, SERIAL_INTERFACE_1, I2S_SET, i2s_set);

> > Why does this need to be reset every time, shouldn't we just be setting the
> > register in set_fmt().?

> Yes, I'd sure like to do that, but how do I get to the width in set_fmt()?

Oh, this has some width related thing in it?

> > > +	{ TFA9879_MISC_STATUS,		0x0000 }, /* 0x15, read-only */
> > > +};

> > > +static bool tfa9879_volatile_register(struct device *dev, unsigned
> > > +int reg) {
> > > +	return reg == TFA9879_MISC_STATUS;

> > If the register is volatile it shouldn't have a default value provided.

> Then I misunderstood what volatile was meant to do. I'll just nuke the
> function. It works fine anyway...

A volatile register is one that the chip may change autonomously (eg, an
interrupt status register).

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