Re: [PATCH v2] usb: gadget: uvc: allow changing interface name via configfs

From: John Keeping
Date: Sat Apr 02 2022 - 07:24:37 EST


On Fri, Apr 01, 2022 at 11:04:45AM -0500, Dan Vacura wrote:
> Add a configfs entry, "function_name", to change the iInterface field
> for VideoControl. This name is used on host devices for user selection,
> useful when multiple cameras are present. The default will remain "UVC
> Camera".

> diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
> index 71bb5e477dba..50e6e7a58b41 100644
> --- a/drivers/usb/gadget/function/f_uvc.c
> +++ b/drivers/usb/gadget/function/f_uvc.c
> @@ -44,7 +44,7 @@ MODULE_PARM_DESC(trace, "Trace level bitmask");
> #define UVC_STRING_STREAMING_IDX 1
>
> static struct usb_string uvc_en_us_strings[] = {
> - [UVC_STRING_CONTROL_IDX].s = "UVC Camera",
> + /* [UVC_STRING_CONTROL_IDX].s = DYNAMIC, */
> [UVC_STRING_STREAMING_IDX].s = "Video Streaming",
> { }
> };
> @@ -676,6 +676,7 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
> uvc_hs_streaming_ep.bEndpointAddress = uvc->video.ep->address;
> uvc_ss_streaming_ep.bEndpointAddress = uvc->video.ep->address;
>
> + uvc_en_us_strings[UVC_STRING_CONTROL_IDX].s = opts->function_name;
> us = usb_gstrings_attach(cdev, uvc_function_strings,
> ARRAY_SIZE(uvc_en_us_strings));
> if (IS_ERR(us)) {
> @@ -866,6 +867,7 @@ static struct usb_function_instance *uvc_alloc_inst(void)
>
> opts->streaming_interval = 1;
> opts->streaming_maxpacket = 1024;
> + snprintf(opts->function_name, sizeof(opts->function_name), "UVC Camera");

This only allows a single language to be specified. I know that's what
the existing string uses, but for other strings which can be set by
userspace multiple languages are supported.

Should we be making USB_CONFIG_STRINGS_LANG more generic so that it can
be used by functions as well as the core configfs code?