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