Re: [alsa-devel] [PATCH V2 06/10] ASoC: img: Add driver for parallel output controller

[Mark Brown <broonie@kernel.org>]

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On Thu, Oct 22, 2015 at 08:21:03PM +0100, Damien Horsley wrote:
> On 19/10/15 19:07, Mark Brown wrote:
> > On Mon, Oct 12, 2015 at 01:40:33PM +0100, Damien Horsley wrote:

> >> +	spin_lock_irqsave(&prl->lock, flags);
> >> +	reg = img_prl_out_readl(prl, IMG_PRL_OUT_CTL);
> >> +	ucontrol->value.integer.value[0] = !!(reg & IMG_PRL_OUT_CTL_EDGE_MASK);
> >> +	spin_unlock_irqrestore(&prl->lock, flags);

> > Do you need to lock a single register read?

> Between the calls to reset_control_assert and reset_control_deassert,
> the block is held in reset. During this time, no register access will
> succeed. All register access that may occur concurrently with the reset
> needs to be locked

Add a comment so readers know this.

> >> +static struct snd_kcontrol_new img_prl_out_controls[] = {
> >> +	{
> >> +		.iface = SNDRV_CTL_ELEM_IFACE_PCM,
> >> +		.name = "Parallel Out Edge Falling",
> >> +		.info = img_prl_out_edge_info,
> >> +		.get = img_prl_out_get_edge,
> >> +		.put = img_prl_out_set_edge
> >> +	}
> >> +};

> > If this is a boolean control (it looked like one) it should be called
> > Switch but it's not clear to me what exactly is being controlled here or
> > why it's something that should be exposed to userspace.

> This controls the edge (rising/falling) of the frame clock that the
> samples are generated on. Should I create a set_fmt function and use
> SND_SOC_DAIFMT_NB_NF / SND_SOC_DAIFMT_NB_IF to set this instead? I
> wasn't sure if those formats were just for I2S or not

Yes, that's part of the DAI format - and we definitely don't want users
randomly changing this at runtime, the CODEC and CPU need to be
configured together.

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