/* * 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/nls.h> #include <linux/usb/ch9.h> #include <linux/usb/gadget.h> /** * 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, must be 16-bit aligned * * 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)); len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN, (wchar_t *) &buf[2], 126); if (len < 0) return -EINVAL; buf [0] = (len + 1) * 2; buf [1] = USB_DT_STRING; return buf [0]; }