[PATCH v24 20/34] ALSA: usb-audio: Introduce USB SND platform op callbacks

Wesley Cheng
2024-08-01T01:18:45Z

Allow for different platforms to be notified on USB SND connect/disconnect
seqeunces. 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 | 9 ++++++++
2 files changed, 62 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index bdb04fa37a71..bb98ea45d1d7 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);

/*
* disconnect streams
@@ -914,7 +950,11 @@ 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:
@@ -951,6 +991,9 @@ 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;
@@ -1094,6 +1137,11 @@ 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;
}

@@ -1134,6 +1182,11 @@ 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 6ec95b2edf86..2884912adc96 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -207,4 +207,13 @@ 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);
+};
+
+int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);
+int snd_usb_unregister_platform_ops(void);
#endif /* __USBAUDIO_CARD_H */