linux-kernel - Re: [alsa-devel] [PATCH 1/3] ASoC: twl4030: don't report EBUSY if no change requested.

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Message-ID: <546132EF.7070008@metafoo.de>
Date:	Mon, 10 Nov 2014 22:49:35 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	NeilBrown <neilb@...e.de>
CC:	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	GTA04 owners <gta04-owner@...delico.com>,
	alsa-devel@...a-project.org, Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Liam Girdwood <lgirdwood@...il.com>,
	linux-kernel@...r.kernel.org,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>
Subject: Re: [alsa-devel] [PATCH 1/3] ASoC: twl4030: don't report EBUSY if
 no change requested.

On 11/10/2014 10:45 PM, NeilBrown wrote:
> On Mon, 10 Nov 2014 08:07:50 +0100 Lars-Peter Clausen <lars@...afoo.de> wrote:
>
>> On 11/10/2014 01:45 AM, NeilBrown wrote:
>>> diff --git a/sound/soc/codecs/twl4030.c b/sound/soc/codecs/twl4030.c
>>> index b6b0cb399599..613b61cee081 100644
>>> --- a/sound/soc/codecs/twl4030.c
>>> +++ b/sound/soc/codecs/twl4030.c
>>> @@ -957,6 +957,16 @@ static int snd_soc_put_twl4030_opmode_enum_double(struct snd_kcontrol *kcontrol,
>>>    {
>>>    	struct snd_soc_codec *codec = snd_soc_kcontrol_codec(kcontrol);
>>>    	struct twl4030_priv *twl4030 = snd_soc_codec_get_drvdata(codec);
>>> +	struct snd_ctl_elem_value currentval;
>>>
>>
>> snd_ctl_elem_value is a bit to big to be put onto the kernel stack. Just
>> using twl4030_read() should be fine.
>
> That's a shame, it looked so neat....
>
> Using twl4030_read forces i2c access and misses out on the regmap caching.
>
> What do you think of this?

That looks good, but either snd_soc_kcontrol_component() instead of 
snd_kcontrol_chip() or just snd_soc_read(codec, ...

>
> Thanks,
> NeilBrown
>
> diff --git a/sound/soc/codecs/twl4030.c b/sound/soc/codecs/twl4030.c
> index b6b0cb399599..bdb47a045aa5 100644
> --- a/sound/soc/codecs/twl4030.c
> +++ b/sound/soc/codecs/twl4030.c
> @@ -957,6 +957,18 @@ static int snd_soc_put_twl4030_opmode_enum_double(struct snd_kcontrol *kcontrol,
>   {
>   	struct snd_soc_codec *codec = snd_soc_kcontrol_codec(kcontrol);
>   	struct twl4030_priv *twl4030 = snd_soc_codec_get_drvdata(codec);
> +	const struct soc_enum *e = &twl4030_op_modes_enum;
> +	unsigned int reg_val;
> +	int ret;
> +
> +	ret = snd_soc_component_read(snd_kcontrol_chip(kcontrol),
> +				     e->reg, &reg_val);
> +	if (ret)
> +		return ret;
> +	if (ucontrol->value.enumerated.item[0] ==
> +	    ((reg_val >> e->shift_l) & e->mask))
> +		/* no change requested, so do nothing */
> +		return 0;
>
>   	if (twl4030->configured) {
>   		dev_err(codec->dev,
>

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