ALSA: usb-audio: Introduce USB SND platform op callbacks

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.

Tested-by: Puma Hsu <pumahsu@google.com>
Tested-by: Daehwan Jung <dh10.jung@samsung.com>
Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250409194804.3773260-13-quic_wcheng@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 6c5b0e02e57b0263ab0873f10321e762d001c38b..4ac7f2b8309a3255769d577ba3f53faa3afc8f72 100644 (file)
--- 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 cdafc9e9cecdd2be8fe3db591f8fb249b2c89415..d8b8522e1613f696fbca72239a0fe0b1f6d3f931 100644 (file)
--- 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 */