Re: [PATCH v36 12/31] ALSA: usb-audio: Introduce USB SND platform op callbacks

[Jung Daehwan <dh10.jung@samsung.com>]

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On Fri, Mar 28, 2025 at 03:48:00PM +0800, Puma Hsu wrote:
> On Wed, Mar 19, 2025 at 8:56 AM Wesley Cheng <quic_wcheng@quicinc.com> wrote:
> >
> > Allow for different platforms to be notified on USB SND connect/disconnect
> > sequences.  This allows for platform USB SND modules to properly initialize
> > and populate internal structures with references to the USB SND chip
> > device.
> >
> > Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> 
> Tested-by: Puma Hsu <pumahsu@google.com>
> 

Tested-by: Daehwan Jung <dh10.jung@samsung.com>

> > ---
> >  sound/usb/card.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  sound/usb/card.h | 10 ++++++++++
> >  2 files changed, 59 insertions(+)
> >
> > diff --git a/sound/usb/card.c b/sound/usb/card.c
> > index 6c5b0e02e57b..4ac7f2b8309a 100644
> > --- a/sound/usb/card.c
> > +++ b/sound/usb/card.c
> > @@ -118,6 +118,42 @@ MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no)
> >  static DEFINE_MUTEX(register_mutex);
> >  static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
> >  static struct usb_driver usb_audio_driver;
> > +static struct snd_usb_platform_ops *platform_ops;
> > +
> > +/*
> > + * Register platform specific operations that will be notified on events
> > + * which occur in USB SND.  The platform driver can utilize this path to
> > + * enable features, such as USB audio offloading, which allows for audio data
> > + * to be queued by an audio DSP.
> > + *
> > + * Only one set of platform operations can be registered to USB SND.  The
> > + * platform register operation is protected by the register_mutex.
> > + */
> > +int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops)
> > +{
> > +       guard(mutex)(&register_mutex);
> > +       if (platform_ops)
> > +               return -EEXIST;
> > +
> > +       platform_ops = ops;
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(snd_usb_register_platform_ops);
> > +
> > +/*
> > + * Unregisters the current set of platform operations.  This allows for
> > + * a new set to be registered if required.
> > + *
> > + * The platform unregister operation is protected by the register_mutex.
> > + */
> > +int snd_usb_unregister_platform_ops(void)
> > +{
> > +       guard(mutex)(&register_mutex);
> > +       platform_ops = NULL;
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(snd_usb_unregister_platform_ops);
> >
> >  /*
> >   * Checks to see if requested audio profile, i.e sample rate, # of
> > @@ -954,7 +990,11 @@ static int usb_audio_probe(struct usb_interface *intf,
> >         chip->num_interfaces++;
> >         usb_set_intfdata(intf, chip);
> >         atomic_dec(&chip->active);
> > +
> > +       if (platform_ops && platform_ops->connect_cb)
> > +               platform_ops->connect_cb(chip);
> >         mutex_unlock(&register_mutex);
> > +
> >         return 0;
> >
> >   __error:
> > @@ -991,6 +1031,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
> >         card = chip->card;
> >
> >         mutex_lock(&register_mutex);
> > +       if (platform_ops && platform_ops->disconnect_cb)
> > +               platform_ops->disconnect_cb(chip);
> > +
> >         if (atomic_inc_return(&chip->shutdown) == 1) {
> >                 struct snd_usb_stream *as;
> >                 struct snd_usb_endpoint *ep;
> > @@ -1138,6 +1181,9 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
> >                 chip->system_suspend = chip->num_suspended_intf;
> >         }
> >
> > +       if (platform_ops && platform_ops->suspend_cb)
> > +               platform_ops->suspend_cb(intf, message);
> > +
> >         return 0;
> >  }
> >
> > @@ -1178,6 +1224,9 @@ static int usb_audio_resume(struct usb_interface *intf)
> >
> >         snd_usb_midi_v2_resume_all(chip);
> >
> > +       if (platform_ops && platform_ops->resume_cb)
> > +               platform_ops->resume_cb(intf);
> > +
> >   out:
> >         if (chip->num_suspended_intf == chip->system_suspend) {
> >                 snd_power_change_state(chip->card, SNDRV_CTL_POWER_D0);
> > diff --git a/sound/usb/card.h b/sound/usb/card.h
> > index cdafc9e9cecd..d8b8522e1613 100644
> > --- a/sound/usb/card.h
> > +++ b/sound/usb/card.h
> > @@ -209,7 +209,17 @@ struct snd_usb_stream {
> >         struct list_head list;
> >  };
> >
> > +struct snd_usb_platform_ops {
> > +       void (*connect_cb)(struct snd_usb_audio *chip);
> > +       void (*disconnect_cb)(struct snd_usb_audio *chip);
> > +       void (*suspend_cb)(struct usb_interface *intf, pm_message_t message);
> > +       void (*resume_cb)(struct usb_interface *intf);
> > +};
> > +
> >  struct snd_usb_stream *
> >  snd_usb_find_suppported_substream(int card_idx, struct snd_pcm_hw_params *params,
> >                                   int direction);
> > +
> > +int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);
> > +int snd_usb_unregister_platform_ops(void);
> >  #endif /* __USBAUDIO_CARD_H */
> >
> 
> 

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