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    SubjectRe: [PATCH v9 07/34] ASoC: Add SOC USB APIs for adding an USB backend


    On 10/17/23 15:00, Wesley Cheng wrote:
    > Some platforms may have support for offloading USB audio devices to a
    > dedicated audio DSP. Introduce a set of APIs that allow for management of
    > USB sound card and PCM devices enumerated by the USB SND class driver.
    > This allows for the ASoC components to be aware of what USB devices are

    USB devices or USB endpoints? or both?

    > available for offloading.

    > +/**
    > + * struct snd_soc_usb_device
    > + * @card_idx - sound card index associated with USB device
    > + * @chip_idx - USB sound chip array index
    > + * @num_playback - number of playback streams
    > + * @num_capture - number of capture streams

    presumably excluding explicit feedback streams?

    > + **/
    > +struct snd_soc_usb_device {
    > + int card_idx;
    > + int chip_idx;
    > + int num_playback;
    > + int num_capture;
    > +};
    > +
    > +/**
    > + * struct snd_soc_usb
    > + * @list - list head for SND SOC struct list
    > + * @dev - USB backend device reference
    > + * @component - reference to ASoC component
    > + * @connection_status_cb - callback to notify connection events
    > + * @priv_data - driver data
    > + **/
    > +struct snd_soc_usb {
    > + struct list_head list;
    > + struct device *dev;

    usbdev for consistency with the API below?

    > + struct snd_soc_component *component;

    could you use component only and infer the device from component->dev?

    > + int (*connection_status_cb)(struct snd_soc_usb *usb,
    > + struct snd_soc_usb_device *sdev, bool connected);
    > + void *priv_data;
    > +};
    > +
    > +int snd_soc_usb_connect(struct device *usbdev, struct snd_soc_usb_device *sdev);
    > +int snd_soc_usb_disconnect(struct device *usbdev, struct snd_soc_usb_device *sdev);
    > +void *snd_soc_usb_get_priv_data(struct device *usbdev);
    > +
    > +struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev, void *priv,

    struct device *usbdev for consistency ?

    > + int (*connection_cb)(struct snd_soc_usb *usb,
    > + struct snd_soc_usb_device *sdev, bool connected));
    > +int snd_soc_usb_remove_port(struct device *dev);

    struct device *usbdev for consistency ?


    > +struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev, void *priv,
    > + int (*connection_cb)(struct snd_soc_usb *usb,
    > + struct snd_soc_usb_device *sdev, bool 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;
    > + usb->priv_data = priv;
    > +
    > + 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);
    > +
    > +/**
    > + * 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.

    when the USB backend driver is unbound?

    > + *
    > + */
    > +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;

    can this return void to align with the current trend?

    > +}
    > +EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);
    > +
    > +/**
    > + * 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 DPCM backend selects, which device to enable USB offloading
    > + * on.

    card_idx is not used below, and I don't see how this relates to a
    notification?

    > + *
    > + */
    > +int snd_soc_usb_connect(struct device *usbdev, struct snd_soc_usb_device *sdev)
    > +{
    > + struct snd_soc_usb *ctx;
    > + struct device_node *node;
    > +
    > + if (!usbdev)
    > + return -ENODEV;
    > +
    > + node = snd_soc_find_phandle(usbdev);
    > + if (IS_ERR(node))
    > + return -ENODEV;
    > +
    > + ctx = snd_soc_find_usb_ctx(node);
    > + of_node_put(node);
    > + if (!ctx)
    > + return -ENODEV;
    > +
    > + if (ctx->connection_status_cb)
    > + ctx->connection_status_cb(ctx, sdev, true);
    > +
    > + return 0;
    > +}

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