On 1/25/23 21:14, Wesley Cheng wrote:
> Some platforms may want to register its USB port to be handled by the ASoC
> framework. Audio playback/capture support is also handled entirely by the
> vendor ASoC drivers.
Can you clarify what you mean by 'port'?
> +/**
> + * snd_soc_usb_add_port() - Add a USB backend port
> + * @dev: USB backend device
> + * @connection_cb: connection status callback
> + *
> + * Register a USB backend device to the SND USB SOC framework. Memory is
> + * allocated as part of the USB backend device.
> + *
> + */
> +struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev,
> + int (*connection_cb)(struct snd_soc_usb *usb, int card_idx,
> + int connected))
> +{
> + struct snd_soc_usb *usb;
> +
> + usb = devm_kzalloc(dev, sizeof(*usb), GFP_KERNEL);
> + if (!usb)
> + return ERR_PTR(-ENOMEM);
> +
> + usb->connection_status_cb = connection_cb;
> + usb->dev = dev;
> +
> + mutex_lock(&ctx_mutex);
> + list_add_tail(&usb->list, &usb_ctx_list);
> + mutex_unlock(&ctx_mutex);
> +
> + return usb;
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);
Can a backend have more than one ports?
Is there any relationship between port and USB endpoint, and if yes
where is this determined?
> +
> +/**
> + * snd_soc_usb_remove_port() - Remove a USB backend port
> + * @dev: USB backend device
> + *
> + * Remove a USB backend device from USB SND SOC. Memory is freed when USB
> + * backend is removed.
> + *
> + */
> +int snd_soc_usb_remove_port(struct device *dev)
> +{
> + struct snd_soc_usb *ctx, *tmp;
> +
> + mutex_lock(&ctx_mutex);
> + list_for_each_entry_safe(ctx, tmp, &usb_ctx_list, list) {
> + if (ctx->dev == dev) {
> + list_del(&ctx->list);
> + break;
> + }
> + }
> + mutex_unlock(&ctx_mutex);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);
What happens if the ASoC driver probes/initialize AFTER the USB device
is plugged?
Likewise, can the ASoC driver be removed 'safely' with a fallback to
normal non-offloaded operation happening on remove?
> +
> +/**
> + * snd_soc_usb_connect() - Notification of USB device connection
> + * @usbdev: USB bus device
> + * @card_idx: USB SND card instance
> + *
> + * Notify of a new USB SND device connection. The card_idx can be used to
> + * handle how the USB backend selects, which device to enable offloading on.
> + *
> + */
> +int snd_soc_usb_connect(struct device *usbdev, int card_idx)
> +{
> + struct snd_soc_usb *ctx;
> +
> + if (!usbdev)
> + return -ENODEV;
> +
> + ctx = snd_soc_find_usb_ctx(usbdev);
> + if (!ctx)
> + return -ENODEV;
> +
> + if (ctx->connection_status_cb)
> + ctx->connection_status_cb(ctx, card_idx, 1);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_connect);
> +
> +/**
> + * snd_soc_usb_connect() - Notification of USB device connection
> + * @usbdev: USB bus device
> + *
> + * Notify of a new USB SND device disconnection to the USB backend.
> + *
> + */
> +int snd_soc_usb_disconnect(struct device *usbdev)
> +{
> + struct snd_soc_usb *ctx;
> +
> + if (!usbdev)
> + return -ENODEV;
> +
> + ctx = snd_soc_find_usb_ctx(usbdev);
> + if (!ctx)
> + return -ENODEV;
> +
> + if (ctx->connection_status_cb)
> + ctx->connection_status_cb(ctx, -1, 0);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_disconnect);
Similar concern on connect/disconnect, does this assume any specific
order for the driver probe?
