Re: [PATCH v26 24/33] ALSA: usb-audio: Introduce USB SND platform op callbacks

On 8/29/24 21:40, Wesley Cheng 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

sound/usb/card.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++ sound/usb/card.h | 10 +++++++++ 2 files changed, 63 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c index 1f9dfcd8f336..7f120aa006c0 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

Unregister?

• • 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

@@ -946,7 +982,11 @@ 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:

@@ -983,6 +1023,9 @@ 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;

@@ -1130,6 +1173,11 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message) chip->system_suspend = chip->num_suspended_intf; }

• mutex_lock(&register_mutex);
• if (platform_ops && platform_ops->suspend_cb)

• platform_ops->suspend_cb(intf, message);
  

• mutex_unlock(&register_mutex);
• return 0;

}

@@ -1170,6 +1218,11 @@ static int usb_audio_resume(struct usb_interface *intf)

snd_usb_midi_v2_resume_all(chip);

• mutex_lock(&register_mutex);
• if (platform_ops && platform_ops->resume_cb)

• platform_ops->resume_cb(intf);
  

• mutex_unlock(&register_mutex);
• 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 4f4f3f39b7fa..23d9e6fc69e7 100644 --- a/sound/usb/card.h +++ b/sound/usb/card.h @@ -207,7 +207,17 @@ 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);

+};

You're using the same mutex to protect all four callbacks, so how would things work if e.g. you disconnected a device during the resume operation?