linux-kernel - Re: [RFC PATCH] ALSA: compress: add support to change codec profile in gapless playback

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Date:   Thu, 2 Jul 2020 17:06:02 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     perex@...ex.cz, tiwai@...e.com, lgirdwood@...il.com,
        broonie@...nel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, ckeepax@...nsource.cirrus.com
Subject: Re: [RFC PATCH] ALSA: compress: add support to change codec profile
 in gapless playback

Hi Srini,

On 02-07-20, 12:11, Srinivas Kandagatla wrote:
> For gapless playback its possible that each track can have different

s/its/it is 

> codec profile with same decoder, for example we have WMA album,
> we may have different tracks as WMA v9, WMA v10 and so on
> 
> Existing code does not allow to change this profile while doing gapless
> playback.
> 
> This patch adds new SNDRV_COMPRESS_SET_CODEC_PARAMS IOCTL to allow
> userspace to set this new parameters required for new codec profile.

Thanks, this looks good and in line with discussions done in Audio uConf

> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  include/sound/compress_driver.h       |  5 +++
>  include/sound/soc-component.h         |  3 ++
>  include/sound/soc-dai.h               |  5 +++
>  include/uapi/sound/compress_offload.h |  1 +
>  sound/core/compress_offload.c         | 54 ++++++++++++++++++++++++---
>  sound/soc/soc-compress.c              | 30 +++++++++++++++
>  sound/soc/soc-dai.c                   | 14 +++++++

Can we split the ALSA changes and ASoC changes to different patches
please?

Also please post driver support for this API..

Lastly, documentation needs update about this call

>  7 files changed, 106 insertions(+), 6 deletions(-)
> 
> diff --git a/include/sound/compress_driver.h b/include/sound/compress_driver.h
> index 70cbc5095e72..8d23351f7ad7 100644
> --- a/include/sound/compress_driver.h
> +++ b/include/sound/compress_driver.h
> @@ -93,6 +93,9 @@ struct snd_compr_stream {
>   * @set_params: Sets the compressed stream parameters, mandatory
>   * This can be called in during stream creation only to set codec params
>   * and the stream properties
> + * @set_codec_params: Sets the compressed stream codec parameters, mandatory

This should be optional as gapless is optional

> --- a/include/uapi/sound/compress_offload.h
> +++ b/include/uapi/sound/compress_offload.h
> @@ -172,6 +172,7 @@ struct snd_compr_metadata {
>  						 struct snd_compr_metadata)
>  #define SNDRV_COMPRESS_GET_METADATA	_IOWR('C', 0x15,\
>  						 struct snd_compr_metadata)
> +#define SNDRV_COMPRESS_SET_CODEC_PARAMS	_IOW('C', 0x16, struct snd_codec)
>  #define SNDRV_COMPRESS_TSTAMP		_IOR('C', 0x20, struct snd_compr_tstamp)
>  #define SNDRV_COMPRESS_AVAIL		_IOR('C', 0x21, struct snd_compr_avail)
>  #define SNDRV_COMPRESS_PAUSE		_IO('C', 0x30)

I think we should bump the compress version too for checking in userland
about this support

>  static int snd_compress_check_input(struct snd_compr_params *params)
>  {
>  	/* first let's check the buffer parameter's */
> @@ -574,14 +586,41 @@ static int snd_compress_check_input(struct snd_compr_params *params)
>  	    params->buffer.fragments == 0)
>  		return -EINVAL;
>  
> -	/* now codec parameters */
> -	if (params->codec.id == 0 || params->codec.id > SND_AUDIOCODEC_MAX)
> -		return -EINVAL;
> +	return snd_compress_check_codec_params(&params->codec);

Can this be 1st patch to prepare for this change?

>  
> -	if (params->codec.ch_in == 0 || params->codec.ch_out == 0)
> -		return -EINVAL;
> +}
>  
> -	return 0;
> +static int snd_compr_set_codec_params(struct snd_compr_stream *stream,
> +				      unsigned long arg)
> +{
> +	struct snd_codec *params;
> +	int retval;
> +
> +	if (!stream->ops->set_codec_params)
> +		return -EPERM;
> +
> +	if (stream->runtime->state != SNDRV_PCM_STATE_RUNNING)
> +		return -EPERM;
> +
> +	/* codec params can be only set when next track has been signalled */
> +	if (stream->next_track == false)
> +		return -EPERM;
> +
> +	params = memdup_user((void __user *)arg, sizeof(*params));
> +	if (IS_ERR(params))
> +		return PTR_ERR(params);
> +
> +	retval = snd_compress_check_codec_params(params);
> +	if (retval)
> +		goto out;
> +
> +	retval = stream->ops->set_codec_params(stream, params);
> +	if (retval)
> +		goto out;

this jump is superfluous

> +
> +out:
> +	kfree(params);
> +	return retval;
>  }

...

> +static int soc_compr_set_codec_params(struct snd_compr_stream *cstream,
> +				      struct snd_codec *codec)
> +{
> +	struct snd_soc_pcm_runtime *rtd = cstream->private_data;
> +	struct snd_soc_component *component;
> +	struct snd_soc_dai *cpu_dai = asoc_rtd_to_cpu(rtd, 0);
> +	int i, ret;
> +
> +	mutex_lock_nested(&rtd->card->pcm_mutex, rtd->card->pcm_subclass);
> +
> +	ret = snd_soc_dai_compr_set_codec_params(cpu_dai, cstream, codec);
> +	if (ret < 0)
> +		goto err;
> +
> +	for_each_rtd_components(rtd, i, component) {
> +		if (!component->driver->compress_ops ||
> +		    !component->driver->compress_ops->set_codec_params)
> +			continue;
> +
> +		ret = component->driver->compress_ops->set_codec_params(component, cstream,
> +								     codec);

maybe use a compress_ops pointer to make this look and read better :)
-- 
~Vinod