1// SPDX-License-Identifier: LGPL-2.1+
2/*
3 * Copyright (C) 2003 David Brownell
4 *
5 * Ported to U-Boot by: Thomas Smits <ts.smits@gmail.com> and
6 *                      Remy Bohmer <linux@bohmer.net>
7 */
8
9#include <common.h>
10#include <linux/errno.h>
11#include <linux/usb/ch9.h>
12#include <linux/usb/gadget.h>
13#include <linux/utf.h>
14
15/**
16 * usb_gadget_get_string - fill out a string descriptor
17 * @table: of c strings encoded using UTF-8
18 * @id: string id, from low byte of wValue in get string descriptor
19 * @buf: at least 256 bytes
20 *
21 * Finds the UTF-8 string matching the ID, and converts it into a
22 * string descriptor in utf16-le.
23 * Returns length of descriptor (always even) or negative errno
24 *
25 * If your driver needs stings in multiple languages, you'll probably
26 * "switch (wIndex) { ... }"  in your ep0 string descriptor logic,
27 * using this routine after choosing which set of UTF-8 strings to use.
28 * Note that US-ASCII is a strict subset of UTF-8; any string bytes with
29 * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
30 * characters (which are also widely used in C strings).
31 */
32int
33usb_gadget_get_string(struct usb_gadget_strings *table, int id, u8 *buf)
34{
35	struct usb_string	*s;
36	int			len;
37
38	if (!table)
39		return -EINVAL;
40
41	/* descriptor 0 has the language id */
42	if (id == 0) {
43		buf[0] = 4;
44		buf[1] = USB_DT_STRING;
45		buf[2] = (u8) table->language;
46		buf[3] = (u8) (table->language >> 8);
47		return 4;
48	}
49	for (s = table->strings; s && s->s; s++)
50		if (s->id == id)
51			break;
52
53	/* unrecognized: stall. */
54	if (!s || !s->s)
55		return -EINVAL;
56
57	/* string descriptors have length, tag, then UTF16-LE text */
58	len = min((size_t) 126, strlen(s->s));
59	memset(buf + 2, 0, 2 * len);	/* zero all the bytes */
60	len = utf8_to_utf16le(s->s, (__le16 *)&buf[2], len);
61	if (len < 0)
62		return -EINVAL;
63	buf[0] = (len + 1) * 2;
64	buf[1] = USB_DT_STRING;
65	return buf[0];
66}
67