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/module.h> 13 #include <linux/list.h> 14 #include <linux/string.h> 15 #include <linux/device.h> 16 #include <linux/init.h> 17 #include <linux/nls.h> 18 19 #include <linux/usb/ch9.h> 20 #include <linux/usb/gadget.h> 21 22 23 /** 24 * usb_gadget_get_string - fill out a string descriptor 25 * @table: of c strings encoded using UTF-8 26 * @id: string id, from low byte of wValue in get string descriptor 27 * @buf: at least 256 bytes, must be 16-bit aligned 28 * 29 * Finds the UTF-8 string matching the ID, and converts it into a 30 * string descriptor in utf16-le. 31 * Returns length of descriptor (always even) or negative errno 32 * 33 * If your driver needs stings in multiple languages, you'll probably 34 * "switch (wIndex) { ... }" in your ep0 string descriptor logic, 35 * using this routine after choosing which set of UTF-8 strings to use. 36 * Note that US-ASCII is a strict subset of UTF-8; any string bytes with 37 * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1 38 * characters (which are also widely used in C strings). 39 */ 40 int 41 usb_gadget_get_string (struct usb_gadget_strings *table, int id, u8 *buf) 42 { 43 struct usb_string *s; 44 int len; 45 46 /* descriptor 0 has the language id */ 47 if (id == 0) { 48 buf [0] = 4; 49 buf [1] = USB_DT_STRING; 50 buf [2] = (u8) table->language; 51 buf [3] = (u8) (table->language >> 8); 52 return 4; 53 } 54 for (s = table->strings; s && s->s; s++) 55 if (s->id == id) 56 break; 57 58 /* unrecognized: stall. */ 59 if (!s || !s->s) 60 return -EINVAL; 61 62 /* string descriptors have length, tag, then UTF16-LE text */ 63 len = min ((size_t) 126, strlen (s->s)); 64 len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN, 65 (wchar_t *) &buf[2], 126); 66 if (len < 0) 67 return -EINVAL; 68 buf [0] = (len + 1) * 2; 69 buf [1] = USB_DT_STRING; 70 return buf [0]; 71 } 72 EXPORT_SYMBOL_GPL(usb_gadget_get_string); 73