Re: [PATCH v36 08/31] ALSA: usb-audio: Export USB SND APIs for modules

[Puma Hsu]

On Wed, Mar 19, 2025 at 8:52 AM Wesley Cheng <quic_wcheng@xxxxxxxxxxx> wrote:
>
> Some vendor modules will utilize useful parsing and endpoint management
> APIs to start audio playback/capture.
>
> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>

Tested-by: Puma Hsu <pumahsu@xxxxxxxxxx>

> ---
>  sound/usb/card.c     |  4 +++
>  sound/usb/endpoint.c |  1 +
>  sound/usb/helper.c   |  1 +
>  sound/usb/pcm.c      | 75 +++++++++++++++++++++++++++++++-------------
>  sound/usb/pcm.h      | 11 +++++++
>  5 files changed, 71 insertions(+), 21 deletions(-)
>
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 9c411b82a218..a0087bde684c 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -1030,6 +1030,7 @@ 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)
> @@ -1038,6 +1039,7 @@ 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)
>  {
> @@ -1060,6 +1062,7 @@ 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)
>  {
> @@ -1073,6 +1076,7 @@ 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 a29f28eb7d0c..1fed039b10ed 100644
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -1524,6 +1524,7 @@ 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 72b671fb2c84..497d2b27fb59 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..18467da6fd9e 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_hw_params(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_hw_params);
>
>  /*
> - * 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_pcm_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_hw_params(subs, hw_params);
> +}
> +
> +int snd_usb_hw_free(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_hw_free);
> +
> +/*
> + * hw_free callback
> + *
> + * reset the audio format and release the buffer
> + */
> +static int snd_usb_pcm_hw_free(struct snd_pcm_substream *substream)
> +{
> +       struct snd_usb_substream *subs = substream->runtime->private_data;
> +
> +       return snd_usb_hw_free(subs);
> +}
>
>  /* free-wheeling mode? (e.g. dmix) */
>  static int in_free_wheeling_mode(struct snd_pcm_runtime *runtime)
> @@ -1746,8 +1779,8 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
>  static const struct snd_pcm_ops snd_usb_playback_ops = {
>         .open =         snd_usb_pcm_open,
>         .close =        snd_usb_pcm_close,
> -       .hw_params =    snd_usb_hw_params,
> -       .hw_free =      snd_usb_hw_free,
> +       .hw_params =    snd_usb_pcm_hw_params,
> +       .hw_free =      snd_usb_pcm_hw_free,
>         .prepare =      snd_usb_pcm_prepare,
>         .trigger =      snd_usb_substream_playback_trigger,
>         .sync_stop =    snd_usb_pcm_sync_stop,
> @@ -1758,8 +1791,8 @@ static const struct snd_pcm_ops snd_usb_playback_ops = {
>  static const struct snd_pcm_ops snd_usb_capture_ops = {
>         .open =         snd_usb_pcm_open,
>         .close =        snd_usb_pcm_close,
> -       .hw_params =    snd_usb_hw_params,
> -       .hw_free =      snd_usb_hw_free,
> +       .hw_params =    snd_usb_pcm_hw_params,
> +       .hw_free =      snd_usb_pcm_hw_free,
>         .prepare =      snd_usb_pcm_prepare,
>         .trigger =      snd_usb_substream_capture_trigger,
>         .sync_stop =    snd_usb_pcm_sync_stop,
> diff --git a/sound/usb/pcm.h b/sound/usb/pcm.h
> index 388fe2ba346d..c096021adb2b 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_hw_params(struct snd_usb_substream *subs,
> +                     struct snd_pcm_hw_params *hw_params);
> +int snd_usb_hw_free(struct snd_usb_substream *subs);
>  #endif /* __USBAUDIO_PCM_H */
>