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/*
* Copyright (C) 2003 David Brownell
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*/
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/string.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>
#include <asm/unaligned.h>
static int utf8_to_utf16le(const char *s, __le16 *cp, unsigned len)
{
int count = 0;
u8 c;
u16 uchar;
/* this insists on correct encodings, though not minimal ones.
* BUT it currently rejects legit 4-byte UTF-8 code points,
* which need surrogate pairs. (Unicode 3.1 can use them.)
*/
while (len != 0 && (c = (u8) *s++) != 0) {
if (unlikely(c & 0x80)) {
// 2-byte sequence:
// 00000yyyyyxxxxxx = 110yyyyy 10xxxxxx
if ((c & 0xe0) == 0xc0) {
uchar = (c & 0x1f) << 6;
c = (u8) *s++;
if ((c & 0xc0) != 0xc0)
goto fail;
c &= 0x3f;
uchar |= c;
// 3-byte sequence (most CJKV characters):
// zzzzyyyyyyxxxxxx = 1110zzzz 10yyyyyy 10xxxxxx
} else if ((c & 0xf0) == 0xe0) {
uchar = (c & 0x0f) << 12;
c = (u8) *s++;
if ((c & 0xc0) != 0xc0)
goto fail;
c &= 0x3f;
uchar |= c << 6;
c = (u8) *s++;
if ((c & 0xc0) != 0xc0)
goto fail;
c &= 0x3f;
uchar |= c;
/* no bogus surrogates */
if (0xd800 <= uchar && uchar <= 0xdfff)
goto fail;
// 4-byte sequence (surrogate pairs, currently rare):
// 11101110wwwwzzzzyy + 110111yyyyxxxxxx
// = 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
// (uuuuu = wwww + 1)
// FIXME accept the surrogate code points (only)
} else
goto fail;
} else
uchar = c;
put_unaligned (cpu_to_le16 (uchar), cp++);
count++;
len--;
}
return count;
fail:
return -1;
}
/**
* 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
*
* 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).
*/
int
usb_gadget_get_string (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));
memset (buf + 2, 0, 2 * len); /* zero all the bytes */
len = utf8_to_utf16le(s->s, (__le16 *)&buf[2], len);
if (len < 0)
return -EINVAL;
buf [0] = (len + 1) * 2;
buf [1] = USB_DT_STRING;
return buf [0];
}
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