Re: [PATCH] ASoc: wm8580: Add the wm8581 codec to the driver

[Charles Keepax <ckeepax@opensource.wolfsonmicro.com>]

On Wed, Oct 19, 2016 at 05:24:35AM +1100, Matt Flax wrote:
> This patch adds support for the wm8581 codec to the wm8580 driver.
> The wm8581 codec hardware adds a fourth DAC and otherwise is
> compatible with the wm8580 codec.
> 
> of_device_id data is used to allow the driver to select the
> suitable DAC count specified in the device tree codec selection.
> The wm8580_driver_data struct is used to store the number of DACs.
> 
> The snd_soc_dai_driver no longer lists the channels_max for the
> playback substream. This variable is set during the i2c probe
> from the of_device_id supplied wm8580_driver_data struct.
> 
> With knowledge of the number of DACs in use, the DAC4 controls,
> widgets and routes are added as required for DAC4.
> 
> The device tree documentation for the wm8580 is altered to list
> the wm8581 codec support, as is the Kconfig file.
> 
> Signed-off-by: Matt Flax <flatmax@flatmax.org>
> ---

When doing a respin of a patch its usually considered good
practice to do something like [PATCH v2] in the subject line,
lets people clearly see that its a new version not a resend.

>  Documentation/devicetree/bindings/sound/wm8580.txt |  4 +-
>  sound/soc/codecs/Kconfig                           |  2 +-
>  sound/soc/codecs/wm8580.c                          | 98 ++++++++++++++++++++--
>  3 files changed, 92 insertions(+), 12 deletions(-)
<snip>
> @@ -65,6 +68,8 @@
>  #define WM8580_DIGITAL_ATTENUATION_DACR2     0x17
>  #define WM8580_DIGITAL_ATTENUATION_DACL3     0x18
>  #define WM8580_DIGITAL_ATTENUATION_DACR3     0x19
> +#define WM8580_DIGITAL_ATTENUATION_DACL4     0x1A
> +#define WM8580_DIGITAL_ATTENUATION_DACR4     0x1B

Apologies my fault for still not being clear these two new
defines would still be best called WM8581...

<snip>
> +static int wm8580_playback_startup(struct snd_pcm_substream *substream,
> +			   struct snd_soc_dai *dai)
> +{
> +	struct snd_soc_codec *codec = dai->codec;
> +	struct wm8580_priv *wm8580 = snd_soc_codec_get_drvdata(codec);
> +
> +	return snd_pcm_hw_constraint_single(substream->runtime,
> +		SNDRV_PCM_HW_PARAM_CHANNELS, wm8580->drvdata->num_dacs * 2);

Won't this limit us to exactly num_dacs * 2 channels? I would
have expected a contraint_minmax, I haven't checked the core
code but would be good to know you have tested smaller numbers
of channels and they are working. Bearing in mind that some
user-space applications will do things like pad out to the number
of channels the hardware claims to require. For example for aplay
I believe -v will show you if it does any conversion and
--disable-channels will stop it attempting to convert the number
of channels.

Apart from those very small comments this all looks fine to me.

Thanks,
Charles