// SPDX-License-Identifier: LGPL-2.1+/* * Copyright (C) 2003 David Brownell */ #include <linux/errno.h>#include <linux/kernel.h>#include <linux/module.h>#include <linux/list.h>#include <linux/string.h>#include <linux/device.h>#include <linux/nls.h> #include <linux/usb/ch9.h>#include <linux/usb/gadget.h>  /** * usb_gadget_get_string - fill out a string descriptor  * @table: of c strings encoded using UTF-8 * @id: string id, from low byte of wValue in get string descriptor * @buf: at least 256 bytes, must be 16-bit aligned * * Finds the UTF-8 string matching the ID, and converts it into a * string descriptor in utf16-le. * Returns length of descriptor (always even) or negative errno * * If your driver needs stings in multiple languages, you'll probably * "switch (wIndex) { ... }"  in your ep0 string descriptor logic, * using this routine after choosing which set of UTF-8 strings to use. * Note that US-ASCII is a strict subset of UTF-8; any string bytes with * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1 * characters (which are also widely used in C strings). */intusb_gadget_get_string (const struct usb_gadget_strings *table, int id, u8 *buf){	struct usb_string	*s;	int			len; 	/* descriptor 0 has the language id */	if (id == 0) {		buf [0] = 4;		buf [1] = USB_DT_STRING;		buf [2] = (u8) table->language;		buf [3] = (u8) (table->language >> 8);		return 4;	}	for (s = table->strings; s && s->s; s++)		if (s->id == id)			break; 	/* unrecognized: stall. */	if (!s || !s->s)		return -EINVAL; 	/* string descriptors have length, tag, then UTF16-LE text */	len = min ((size_t) 126, strlen (s->s));	len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,			(wchar_t *) &buf[2], 126);	if (len < 0)		return -EINVAL;	buf [0] = (len + 1) * 2;	buf [1] = USB_DT_STRING;	return buf [0];}EXPORT_SYMBOL_GPL(usb_gadget_get_string);