Re: [PATCH V2] usb: gadget: f_uac1: add adaptive sync support for capture

[Greg KH]

On Wed, Oct 18, 2023 at 03:47:39PM +0800, Charles Yi wrote:
> UAC1 has it's own freerunning clock and can update Host about
> real clock frequency through feedback endpoint so Host can align
> number of samples sent to the UAC1 to prevent overruns/underruns.
> 
> Change UAC1 driver to make it configurable through additional
> 'c_sync' configfs file.
> 
> Default remains 'asynchronous' with possibility to switch it
> to 'adaptive'.
> 
> Changes in V2:
> - Updated the indentation of commit message.
> 
> Signed-off-by: Charles Yi <be286@xxxxxxx>
> ---
>  drivers/usb/gadget/function/f_uac1.c | 30 ++++++++++++++++++++++++++++
>  drivers/usb/gadget/function/u_uac1.h |  2 ++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/usb/gadget/function/f_uac1.c b/drivers/usb/gadget/function/f_uac1.c
> index 6f0e1d803dc2..7a6fcb40bb46 100644
> --- a/drivers/usb/gadget/function/f_uac1.c
> +++ b/drivers/usb/gadget/function/f_uac1.c
> @@ -33,6 +33,8 @@
>  #define FUOUT_EN(_opts) ((_opts)->c_mute_present \
>  			|| (_opts)->c_volume_present)
>  
> +#define EPOUT_FBACK_IN_EN(_opts) ((_opts)->c_sync == USB_ENDPOINT_SYNC_ASYNC)
> +
>  struct f_uac1 {
>  	struct g_audio g_audio;
>  	u8 ac_intf, as_in_intf, as_out_intf;
> @@ -227,6 +229,16 @@ static struct uac_iso_endpoint_descriptor as_iso_out_desc = {
>  	.wLockDelay =		cpu_to_le16(1),
>  };
>  
> +static struct usb_endpoint_descriptor as_fback_ep_desc = {
> +	.bLength = USB_DT_ENDPOINT_SIZE,
> +	.bDescriptorType = USB_DT_ENDPOINT,
> +
> +	.bEndpointAddress = USB_DIR_IN,
> +	.bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_USAGE_FEEDBACK,
> +	.wMaxPacketSize = cpu_to_le16(3),
> +	.bInterval = 1,
> +};
> +
>  static struct uac_format_type_i_discrete_descriptor as_in_type_i_desc = {
>  	.bLength =		0, /* filled on rate setup */
>  	.bDescriptorType =	USB_DT_CS_INTERFACE,
> @@ -280,6 +292,7 @@ static struct usb_descriptor_header *f_audio_desc[] = {
>  
>  	(struct usb_descriptor_header *)&as_out_ep_desc,
>  	(struct usb_descriptor_header *)&as_iso_out_desc,
> +	(struct usb_descriptor_header *)&as_fback_ep_desc,
>  
>  	(struct usb_descriptor_header *)&as_in_interface_alt_0_desc,
>  	(struct usb_descriptor_header *)&as_in_interface_alt_1_desc,
> @@ -1107,6 +1120,9 @@ static void setup_descriptor(struct f_uac1_opts *opts)
>  		f_audio_desc[i++] = USBDHDR(&as_out_type_i_desc);
>  		f_audio_desc[i++] = USBDHDR(&as_out_ep_desc);
>  		f_audio_desc[i++] = USBDHDR(&as_iso_out_desc);
> +		if (EPOUT_FBACK_IN_EN(opts)) {
> +			f_audio_desc[i++] = USBDHDR(&as_fback_ep_desc);
> +		}
>  	}
>  	if (EPIN_EN(opts)) {
>  		f_audio_desc[i++] = USBDHDR(&as_in_interface_alt_0_desc);
> @@ -1317,6 +1333,12 @@ static int f_audio_bind(struct usb_configuration *c, struct usb_function *f)
>  		ac_header_desc->baInterfaceNr[ba_iface_id++] = status;
>  		uac1->as_out_intf = status;
>  		uac1->as_out_alt = 0;
> +
> +		if (EPOUT_FBACK_IN_EN(audio_opts)) {
> +			as_out_ep_desc.bmAttributes =
> +			USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC;
> +			as_out_interface_alt_1_desc.bNumEndpoints++;
> +		}
>  	}
>  
>  	if (EPIN_EN(audio_opts)) {
> @@ -1354,6 +1376,12 @@ static int f_audio_bind(struct usb_configuration *c, struct usb_function *f)
>  			goto err_free_fu;
>  		audio->out_ep = ep;
>  		audio->out_ep->desc = &as_out_ep_desc;
> +		if (EPOUT_FBACK_IN_EN(audio_opts)) {
> +			audio->in_ep_fback = usb_ep_autoconfig(gadget, &as_fback_ep_desc);
> +			if (!audio->in_ep_fback) {
> +				goto err_free_fu;
> +			}
> +		}
>  	}
>  
>  	if (EPIN_EN(audio_opts)) {
> @@ -1685,6 +1713,8 @@ static struct usb_function_instance *f_audio_alloc_inst(void)
>  
>  	opts->req_number = UAC1_DEF_REQ_NUM;
>  
> +	opts->c_sync = UAC1_DEF_CSYNC;
> +
>  	snprintf(opts->function_name, sizeof(opts->function_name), "AC Interface");
>  
>  	return &opts->func_inst;
> diff --git a/drivers/usb/gadget/function/u_uac1.h b/drivers/usb/gadget/function/u_uac1.h
> index f7a616760e31..c6e2271e8cdd 100644
> --- a/drivers/usb/gadget/function/u_uac1.h
> +++ b/drivers/usb/gadget/function/u_uac1.h
> @@ -27,6 +27,7 @@
>  #define UAC1_DEF_MAX_DB		0		/* 0 dB */
>  #define UAC1_DEF_RES_DB		(1*256)	/* 1 dB */
>  
> +#define UAC1_DEF_CSYNC		USB_ENDPOINT_SYNC_ASYNC
>  
>  struct f_uac1_opts {
>  	struct usb_function_instance	func_inst;
> @@ -56,6 +57,7 @@ struct f_uac1_opts {
>  
>  	struct mutex			lock;
>  	int				refcnt;
> +	int				c_sync;
>  };
>  
>  #endif /* __U_UAC1_H */
> -- 
> 2.34.1
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
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created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
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