[PATCH v3 11/11] usb: gadget: uvc: Use custom strings if available

[Daniel Scally <dan.scally@ideasonboard.com>]

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>
---
Changes in v3:

	- Dropped the VideoControl description since there's an attribute for
	that now

Changes in v2:

	- New patch

 drivers/usb/gadget/function/f_uvc.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 642ab210abb1..7bce5e5f226a 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -731,6 +731,10 @@ 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));
@@ -738,11 +742,15 @@ 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)
-- 
2.34.1