> +/**
> + * struct snd_soc_usb_device
> + * @card_idx - sound card index associated with USB device
> + * @pcm_idx - PCM device index associated with USB device
> + * @chip_idx - USB sound chip array index
> + * @num_playback - number of playback streams
> + * @num_capture - number of capture streams
so here we have a clear separation between playback and capture...
> + * @list - list head for SoC USB devices
> + **/
> +struct snd_soc_usb_device {
> + int card_idx;
> + int pcm_idx;
> + int chip_idx;
> + int num_playback;
> + int num_capture;
> + struct list_head list;
> +};
> +
> +/**
> + * struct snd_soc_usb
> + * @list - list head for SND SOC struct list
> + * @component - reference to ASoC component
> + * @num_supported_streams - number of supported concurrent sessions
... but here we don't. And it's not clear what the working 'sessions'
means in the comment.
> + * @connection_status_cb - callback to notify connection events
> + * @priv_data - driver data
> + **/
> +struct snd_soc_usb {
> + struct list_head list;
> + struct snd_soc_component *component;
> + unsigned int num_supported_streams;
> + int (*connection_status_cb)(struct snd_soc_usb *usb,
> + struct snd_soc_usb_device *sdev, bool connected);
> + void *priv_data;
> +};
> +/**
> + * snd_soc_usb_allocate_port() - allocate a SOC USB device
USB port?
> + * @component: USB DPCM backend DAI component
> + * @num_streams: number of offloading sessions supported
same comment, is this direction-specific or not?
> + * @data: private data
> + *
> + * Allocate and initialize a SOC USB device. This will populate parameters that
> + * are used in subsequent sequences.
> + *
> + */
> +struct snd_soc_usb *snd_soc_usb_allocate_port(struct snd_soc_component *component,
> + int num_streams, void *data)
> +{
> + struct snd_soc_usb *usb;
> +
> + usb = kzalloc(sizeof(*usb), GFP_KERNEL);
> + if (!usb)
> + return ERR_PTR(-ENOMEM);
> +
> + usb->component = component;
> + usb->priv_data = data;
> + usb->num_supported_streams = num_streams;
> +
> + return usb;
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_allocate_port);
> +
> +/**
> + * snd_soc_usb_free_port() - free a SOC USB device
> + * @usb: allocated SOC USB device
> +
> + * Free and remove the SOC USB device from the available list of devices.
Now I am lost again on the device:port relationship. I am sure you've
explained this before but I forget things and the code isn't
self-explanatory.
> + *
> + */
> +void snd_soc_usb_free_port(struct snd_soc_usb *usb)
> +{
> + snd_soc_usb_remove_port(usb);
> + kfree(usb);
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_free_port);
> +
> +/**
> + * snd_soc_usb_add_port() - Add a USB backend port
> + * @usb: soc usb device to add
> + *
> + * Register a USB backend device to the SND USB SOC framework. Memory is
> + * allocated as part of the USB backend device.
> + *
> + */
> +void snd_soc_usb_add_port(struct snd_soc_usb *usb)
> +{
> + mutex_lock(&ctx_mutex);
> + list_add_tail(&usb->list, &usb_ctx_list);
> + mutex_unlock(&ctx_mutex);
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);
> +
> +/**
> + * snd_soc_usb_remove_port() - Remove a USB backend port
> + * @usb: soc usb device to remove
> + *
> + * Remove a USB backend device from USB SND SOC. Memory is freed when USB
> + * backend is removed.
> + *
> + */
> +void snd_soc_usb_remove_port(struct snd_soc_usb *usb)
> +{
> + struct snd_soc_usb *ctx, *tmp;
> +
> + mutex_lock(&ctx_mutex);
> + list_for_each_entry_safe(ctx, tmp, &usb_ctx_list, list) {
> + if (ctx == usb) {
> + list_del(&ctx->list);
> + break;
> + }
> + }
> + mutex_unlock(&ctx_mutex);
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);
