137 lines
3.4 KiB
C
137 lines
3.4 KiB
C
/*
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* Copyright (C) 2003 David Brownell
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published
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* by the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*/
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/string.h>
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#include <linux/device.h>
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#include <linux/init.h>
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#include <linux/usb_ch9.h>
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#include <linux/usb_gadget.h>
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#include <asm/unaligned.h>
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static int utf8_to_utf16le(const char *s, __le16 *cp, unsigned len)
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{
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int count = 0;
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u8 c;
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u16 uchar;
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/* this insists on correct encodings, though not minimal ones.
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* BUT it currently rejects legit 4-byte UTF-8 code points,
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* which need surrogate pairs. (Unicode 3.1 can use them.)
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*/
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while (len != 0 && (c = (u8) *s++) != 0) {
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if (unlikely(c & 0x80)) {
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// 2-byte sequence:
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// 00000yyyyyxxxxxx = 110yyyyy 10xxxxxx
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if ((c & 0xe0) == 0xc0) {
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uchar = (c & 0x1f) << 6;
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c = (u8) *s++;
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if ((c & 0xc0) != 0xc0)
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goto fail;
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c &= 0x3f;
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uchar |= c;
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// 3-byte sequence (most CJKV characters):
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// zzzzyyyyyyxxxxxx = 1110zzzz 10yyyyyy 10xxxxxx
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} else if ((c & 0xf0) == 0xe0) {
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uchar = (c & 0x0f) << 12;
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c = (u8) *s++;
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if ((c & 0xc0) != 0xc0)
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goto fail;
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c &= 0x3f;
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uchar |= c << 6;
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c = (u8) *s++;
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if ((c & 0xc0) != 0xc0)
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goto fail;
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c &= 0x3f;
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uchar |= c;
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/* no bogus surrogates */
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if (0xd800 <= uchar && uchar <= 0xdfff)
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goto fail;
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// 4-byte sequence (surrogate pairs, currently rare):
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// 11101110wwwwzzzzyy + 110111yyyyxxxxxx
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// = 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
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// (uuuuu = wwww + 1)
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// FIXME accept the surrogate code points (only)
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} else
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goto fail;
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} else
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uchar = c;
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put_unaligned (cpu_to_le16 (uchar), cp++);
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count++;
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len--;
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}
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return count;
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fail:
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return -1;
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}
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/**
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* usb_gadget_get_string - fill out a string descriptor
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* @table: of c strings encoded using UTF-8
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* @id: string id, from low byte of wValue in get string descriptor
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* @buf: at least 256 bytes
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*
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* Finds the UTF-8 string matching the ID, and converts it into a
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* string descriptor in utf16-le.
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* Returns length of descriptor (always even) or negative errno
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*
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* If your driver needs stings in multiple languages, you'll probably
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* "switch (wIndex) { ... }" in your ep0 string descriptor logic,
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* using this routine after choosing which set of UTF-8 strings to use.
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* Note that US-ASCII is a strict subset of UTF-8; any string bytes with
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* the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
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* characters (which are also widely used in C strings).
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*/
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int
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usb_gadget_get_string (struct usb_gadget_strings *table, int id, u8 *buf)
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{
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struct usb_string *s;
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int len;
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/* descriptor 0 has the language id */
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if (id == 0) {
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buf [0] = 4;
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buf [1] = USB_DT_STRING;
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buf [2] = (u8) table->language;
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buf [3] = (u8) (table->language >> 8);
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return 4;
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}
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for (s = table->strings; s && s->s; s++)
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if (s->id == id)
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break;
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/* unrecognized: stall. */
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if (!s || !s->s)
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return -EINVAL;
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/* string descriptors have length, tag, then UTF16-LE text */
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len = min ((size_t) 126, strlen (s->s));
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memset (buf + 2, 0, 2 * len); /* zero all the bytes */
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len = utf8_to_utf16le(s->s, (__le16 *)&buf[2], len);
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if (len < 0)
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return -EINVAL;
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buf [0] = (len + 1) * 2;
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buf [1] = USB_DT_STRING;
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return buf [0];
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}
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