/* * 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_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]; }