drivers/usb/gadget/usbstring.c

   1 /*
   2  * Copyright (C) 2003 David Brownell
   3  *
   4  * SPDX-License-Identifier:     LGPL-2.1+
   5  *
   6  * Ported to U-boot by: Thomas Smits <ts.smits@gmail.com> and
   7  *                      Remy Bohmer <linux@bohmer.net>
   8  */
   9
  10 #include <common.h>
  11 #include <asm/errno.h>
  12 #include <linux/usb/ch9.h>
  13 #include <linux/usb/gadget.h>
  14
  15 #include <asm/unaligned.h>
  16
  17
  18 static int utf8_to_utf16le(const char *s, __le16 *cp, unsigned len)
  19 {
  20         int     count = 0;
  21         u8      c;
  22         u16     uchar;
  23
  24         /*
  25          * this insists on correct encodings, though not minimal ones.
  26          * BUT it currently rejects legit 4-byte UTF-8 code points,
  27          * which need surrogate pairs.  (Unicode 3.1 can use them.)
  28          */
  29         while (len != 0 && (c = (u8) *s++) != 0) {
  30                 if ((c & 0x80)) {
  31                         /*
  32                          * 2-byte sequence:
  33                          * 00000yyyyyxxxxxx = 110yyyyy 10xxxxxx
  34                          */
  35                         if ((c & 0xe0) == 0xc0) {
  36                                 uchar = (c & 0x1f) << 6;
  37
  38                                 c = (u8) *s++;
  39                                 if ((c & 0xc0) != 0x80)
  40                                         goto fail;
  41                                 c &= 0x3f;
  42                                 uchar |= c;
  43
  44                         /*
  45                          * 3-byte sequence (most CJKV characters):
  46                          * zzzzyyyyyyxxxxxx = 1110zzzz 10yyyyyy 10xxxxxx
  47                          */
  48                         } else if ((c & 0xf0) == 0xe0) {
  49                                 uchar = (c & 0x0f) << 12;
  50
  51                                 c = (u8) *s++;
  52                                 if ((c & 0xc0) != 0x80)
  53                                         goto fail;
  54                                 c &= 0x3f;
  55                                 uchar |= c << 6;
  56
  57                                 c = (u8) *s++;
  58                                 if ((c & 0xc0) != 0x80)
  59                                         goto fail;
  60                                 c &= 0x3f;
  61                                 uchar |= c;
  62
  63                                 /* no bogus surrogates */
  64                                 if (0xd800 <= uchar && uchar <= 0xdfff)
  65                                         goto fail;
  66
  67                         /*
  68                          * 4-byte sequence (surrogate pairs, currently rare):
  69                          * 11101110wwwwzzzzyy + 110111yyyyxxxxxx
  70                          *     = 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
  71                          * (uuuuu = wwww + 1)
  72                          * FIXME accept the surrogate code points (only)
  73                          */
  74                         } else
  75                                 goto fail;
  76                 } else
  77                         uchar = c;
  78                 put_unaligned_le16(uchar, cp++);
  79                 count++;
  80                 len--;
  81         }
  82         return count;
  83 fail:
  84         return -1;
  85 }
  86
  87
  88 /**
  89  * usb_gadget_get_string - fill out a string descriptor
  90  * @table: of c strings encoded using UTF-8
  91  * @id: string id, from low byte of wValue in get string descriptor
  92  * @buf: at least 256 bytes
  93  *
  94  * Finds the UTF-8 string matching the ID, and converts it into a
  95  * string descriptor in utf16-le.
  96  * Returns length of descriptor (always even) or negative errno
  97  *
  98  * If your driver needs stings in multiple languages, you'll probably
  99  * "switch (wIndex) { ... }"  in your ep0 string descriptor logic,
 100  * using this routine after choosing which set of UTF-8 strings to use.
 101  * Note that US-ASCII is a strict subset of UTF-8; any string bytes with
 102  * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
 103  * characters (which are also widely used in C strings).
 104  */
 105 int
 106 usb_gadget_get_string(struct usb_gadget_strings *table, int id, u8 *buf)
 107 {
 108         struct usb_string       *s;
 109         int                     len;
 110
 111         /* descriptor 0 has the language id */
 112         if (id == 0) {
 113                 buf[0] = 4;
 114                 buf[1] = USB_DT_STRING;
 115                 buf[2] = (u8) table->language;
 116                 buf[3] = (u8) (table->language >> 8);
 117                 return 4;
 118         }
 119         for (s = table->strings; s && s->s; s++)
 120                 if (s->id == id)
 121                         break;
 122
 123         /* unrecognized: stall. */
 124         if (!s || !s->s)
 125                 return -EINVAL;
 126
 127         /* string descriptors have length, tag, then UTF16-LE text */
 128         len = min((size_t) 126, strlen(s->s));
 129         memset(buf + 2, 0, 2 * len);    /* zero all the bytes */
 130         len = utf8_to_utf16le(s->s, (__le16 *)&buf[2], len);
 131         if (len < 0)
 132                 return -EINVAL;
 133         buf[0] = (len + 1) * 2;
 134         buf[1] = USB_DT_STRING;
 135         return buf[0];
 136 }