Re: [PATCH v5 12/32] sound: usb: Export USB SND APIs for modules

["Amadeusz Sławiński" <amadeuszx.slawinski@linux.intel.com>]

On 8/29/2023 11:06 PM, Wesley Cheng wrote:
> Some vendor modules will utilize useful parsing and endpoint management
> APIs to start audio playback/capture.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> ---
>   sound/usb/card.c     |  4 +++
>   sound/usb/endpoint.c |  1 +
>   sound/usb/helper.c   |  1 +
>   sound/usb/pcm.c      | 67 +++++++++++++++++++++++++++++++++-----------
>   sound/usb/pcm.h      | 11 ++++++++
>   5 files changed, 67 insertions(+), 17 deletions(-)
> 
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 067a1e82f4bf..b45b6daee7b7 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -1053,6 +1053,7 @@ int snd_usb_lock_shutdown(struct snd_usb_audio *chip)
>   		wake_up(&chip->shutdown_wait);
>   	return err;
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_lock_shutdown);
>   
>   /* autosuspend and unlock the shutdown */
>   void snd_usb_unlock_shutdown(struct snd_usb_audio *chip)
> @@ -1061,6 +1062,7 @@ void snd_usb_unlock_shutdown(struct snd_usb_audio *chip)
>   	if (atomic_dec_and_test(&chip->usage_count))
>   		wake_up(&chip->shutdown_wait);
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_unlock_shutdown);
>   
>   int snd_usb_autoresume(struct snd_usb_audio *chip)
>   {
> @@ -1083,6 +1085,7 @@ int snd_usb_autoresume(struct snd_usb_audio *chip)
>   	}
>   	return 0;
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_autoresume);
>   
>   void snd_usb_autosuspend(struct snd_usb_audio *chip)
>   {
> @@ -1096,6 +1099,7 @@ void snd_usb_autosuspend(struct snd_usb_audio *chip)
>   	for (i = 0; i < chip->num_interfaces; i++)
>   		usb_autopm_put_interface(chip->intf[i]);
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_autosuspend);
>   
>   static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
>   {
> diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
> index a385e85c4650..aac92e0b8aa2 100644
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -1503,6 +1503,7 @@ int snd_usb_endpoint_prepare(struct snd_usb_audio *chip,
>   	mutex_unlock(&chip->mutex);
>   	return err;
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_endpoint_prepare);
>   
>   /* get the current rate set to the given clock by any endpoint */
>   int snd_usb_endpoint_get_clock_rate(struct snd_usb_audio *chip, int clock)
> diff --git a/sound/usb/helper.c b/sound/usb/helper.c
> index bf80e55d013a..4322ae3738e6 100644
> --- a/sound/usb/helper.c
> +++ b/sound/usb/helper.c
> @@ -62,6 +62,7 @@ void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype
>   	}
>   	return NULL;
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_find_csint_desc);
>   
>   /*
>    * Wrapper for usb_control_msg().
> diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> index 08bf535ed163..999f66080649 100644
> --- a/sound/usb/pcm.c
> +++ b/sound/usb/pcm.c
> @@ -148,6 +148,16 @@ find_format(struct list_head *fmt_list_head, snd_pcm_format_t format,
>   	return found;
>   }
>   
> +const struct audioformat *
> +snd_usb_find_format(struct list_head *fmt_list_head, snd_pcm_format_t format,
> +	    unsigned int rate, unsigned int channels, bool strict_match,
> +	    struct snd_usb_substream *subs)
> +{
> +	return find_format(fmt_list_head, format, rate, channels, strict_match,
> +			subs);
> +}
> +EXPORT_SYMBOL_GPL(snd_usb_find_format);
> +
>   static const struct audioformat *
>   find_substream_format(struct snd_usb_substream *subs,
>   		      const struct snd_pcm_hw_params *params)
> @@ -157,6 +167,14 @@ find_substream_format(struct snd_usb_substream *subs,
>   			   true, subs);
>   }
>   
> +const struct audioformat *
> +snd_usb_find_substream_format(struct snd_usb_substream *subs,
> +		      const struct snd_pcm_hw_params *params)
> +{
> +	return find_substream_format(subs, params);
> +}
> +EXPORT_SYMBOL_GPL(snd_usb_find_substream_format);
> +
>   bool snd_usb_pcm_has_fixed_rate(struct snd_usb_substream *subs)
>   {
>   	const struct audioformat *fp;
> @@ -461,20 +479,9 @@ static void close_endpoints(struct snd_usb_audio *chip,
>   	}
>   }
>   
> -/*
> - * hw_params callback
> - *
> - * allocate a buffer and set the given audio format.
> - *
> - * so far we use a physically linear buffer although packetize transfer
> - * doesn't need a continuous area.
> - * if sg buffer is supported on the later version of alsa, we'll follow
> - * that.
> - */
> -static int snd_usb_hw_params(struct snd_pcm_substream *substream,
> -			     struct snd_pcm_hw_params *hw_params)
> +int snd_usb_attach_endpoints(struct snd_usb_substream *subs,
> +				struct snd_pcm_hw_params *hw_params)
>   {
> -	struct snd_usb_substream *subs = substream->runtime->private_data;
>   	struct snd_usb_audio *chip = subs->stream->chip;
>   	const struct audioformat *fmt;
>   	const struct audioformat *sync_fmt;
> @@ -499,7 +506,7 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
>   	if (fmt->implicit_fb) {
>   		sync_fmt = snd_usb_find_implicit_fb_sync_format(chip, fmt,
>   								hw_params,
> -								!substream->stream,
> +								!subs->direction,
>   								&sync_fixed_rate);
>   		if (!sync_fmt) {
>   			usb_audio_dbg(chip,
> @@ -579,15 +586,28 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
>   
>   	return ret;
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_attach_endpoints);
>   
>   /*
> - * hw_free callback
> + * hw_params callback
>    *
> - * reset the audio format and release the buffer
> + * allocate a buffer and set the given audio format.
> + *
> + * so far we use a physically linear buffer although packetize transfer
> + * doesn't need a continuous area.
> + * if sg buffer is supported on the later version of alsa, we'll follow
> + * that.
>    */
> -static int snd_usb_hw_free(struct snd_pcm_substream *substream)
> +static int snd_usb_hw_params(struct snd_pcm_substream *substream,
> +			     struct snd_pcm_hw_params *hw_params)
>   {
>   	struct snd_usb_substream *subs = substream->runtime->private_data;
> +
> +	return snd_usb_attach_endpoints(subs, hw_params);
> +}
> +
> +int snd_usb_detach_endpoint(struct snd_usb_substream *subs)
> +{
>   	struct snd_usb_audio *chip = subs->stream->chip;
>   
>   	snd_media_stop_pipeline(subs);
> @@ -603,6 +623,19 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
>   
>   	return 0;
>   }
> +EXPORT_SYMBOL_GPL(snd_usb_detach_endpoint);
> +
> +/*
> + * hw_free callback
> + *
> + * reset the audio format and release the buffer
> + */
> +static int snd_usb_hw_free(struct snd_pcm_substream *substream)
> +{
> +	struct snd_usb_substream *subs = substream->runtime->private_data;
> +
> +	return snd_usb_detach_endpoint(subs);
> +}
>   
>   /* free-wheeling mode? (e.g. dmix) */
>   static int in_free_wheeling_mode(struct snd_pcm_runtime *runtime)
> diff --git a/sound/usb/pcm.h b/sound/usb/pcm.h
> index 388fe2ba346d..e36df3611a05 100644
> --- a/sound/usb/pcm.h
> +++ b/sound/usb/pcm.h
> @@ -15,4 +15,15 @@ void snd_usb_preallocate_buffer(struct snd_usb_substream *subs);
>   int snd_usb_audioformat_set_sync_ep(struct snd_usb_audio *chip,
>   				    struct audioformat *fmt);
>   
> +const struct audioformat *
> +snd_usb_find_format(struct list_head *fmt_list_head, snd_pcm_format_t format,
> +	    unsigned int rate, unsigned int channels, bool strict_match,
> +	    struct snd_usb_substream *subs);
> +const struct audioformat *
> +snd_usb_find_substream_format(struct snd_usb_substream *subs,
> +		      const struct snd_pcm_hw_params *params);
> +
> +int snd_usb_attach_endpoints(struct snd_usb_substream *subs,
> +				struct snd_pcm_hw_params *hw_params);
> +int snd_usb_detach_endpoint(struct snd_usb_substream *subs);
>   #endif /* __USBAUDIO_PCM_H */

Why is it multiple "endpoints" when attaching, but only one "endpoint" 
when detaching? Both seem to be getting similar arguments.