usb: gadget: uvc: Use custom strings if available

If the user has defined a custom string descriptor for the IAD or the
VideoStreaming interfaces then set their index field to point to the
custom descriptor instead of the hardcoded defaults. If no custom
descriptors have been linked to, then use the default ones.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230206161802.892954-12-dan.scally@ideasonboard.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 7588ab2..5e919fb 100644 (file)
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -745,6 +745,10 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
                if (xu->string_descriptor_index)
                        xu->desc.iExtension = cdev->usb_strings[xu->string_descriptor_index].id;
 
+       /*
+        * We attach the hard-coded defaults incase the user does not provide
+        * any more appropriate strings through configfs.
+        */
        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));
@@ -752,11 +756,15 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
                ret = PTR_ERR(us);
                goto error;
        }
-       uvc_iad.iFunction = us[UVC_STRING_CONTROL_IDX].id;
-       uvc_control_intf.iInterface = us[UVC_STRING_CONTROL_IDX].id;
-       ret = us[UVC_STRING_STREAMING_IDX].id;
-       uvc_streaming_intf_alt0.iInterface = ret;
-       uvc_streaming_intf_alt1.iInterface = ret;
+
+       uvc_iad.iFunction = opts->iad_index ? cdev->usb_strings[opts->iad_index].id :
+                           us[UVC_STRING_CONTROL_IDX].id;
+       uvc_streaming_intf_alt0.iInterface = opts->vs0_index ?
+                                            cdev->usb_strings[opts->vs0_index].id :
+                                            us[UVC_STRING_STREAMING_IDX].id;
+       uvc_streaming_intf_alt1.iInterface = opts->vs1_index ?
+                                            cdev->usb_strings[opts->vs1_index].id :
+                                            us[UVC_STRING_STREAMING_IDX].id;
 
        /* Allocate interface IDs. */
        if ((ret = usb_interface_id(c, f)) < 0)