usbstring.c revision d80c304bcacaf340efa29364ed0107f5c30378c8 
1/*
2 * Copyright (C) 2003 David Brownell
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU Lesser General Public License as published
6 * by the Free Software Foundation; either version 2.1 of the License, or
7 * (at your option) any later version.
8 */
9
10#include <linux/errno.h>
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/list.h>
14#include <linux/string.h>
15#include <linux/device.h>
16#include <linux/init.h>
17#include <linux/nls.h>
18
19#include <linux/usb/ch9.h>
20#include <linux/usb/gadget.h>
21
22
23/**
24 * usb_gadget_get_string - fill out a string descriptor
25 * @table: of c strings encoded using UTF-8
26 * @id: string id, from low byte of wValue in get string descriptor
27 * @buf: at least 256 bytes, must be 16-bit aligned
28 *
29 * Finds the UTF-8 string matching the ID, and converts it into a
30 * string descriptor in utf16-le.
31 * Returns length of descriptor (always even) or negative errno
32 *
33 * If your driver needs stings in multiple languages, you'll probably
34 * "switch (wIndex) { ... }"  in your ep0 string descriptor logic,
35 * using this routine after choosing which set of UTF-8 strings to use.
36 * Note that US-ASCII is a strict subset of UTF-8; any string bytes with
37 * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
38 * characters (which are also widely used in C strings).
39 */
40int
41usb_gadget_get_string (struct usb_gadget_strings *table, int id, u8 *buf)
42{
43	struct usb_string	*s;
44	int			len;
45
46	/* descriptor 0 has the language id */
47	if (id == 0) {
48		buf [0] = 4;
49		buf [1] = USB_DT_STRING;
50		buf [2] = (u8) table->language;
51		buf [3] = (u8) (table->language >> 8);
52		return 4;
53	}
54	for (s = table->strings; s && s->s; s++)
55		if (s->id == id)
56			break;
57
58	/* unrecognized: stall. */
59	if (!s || !s->s)
60		return -EINVAL;
61
62	/* string descriptors have length, tag, then UTF16-LE text */
63	len = min ((size_t) 126, strlen (s->s));
64	len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
65			(wchar_t *) &buf[2], 126);
66	if (len < 0)
67		return -EINVAL;
68	buf [0] = (len + 1) * 2;
69	buf [1] = USB_DT_STRING;
70	return buf [0];
71}
72EXPORT_SYMBOL_GPL(usb_gadget_get_string);
73