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kernel/linux-imx6_3.14.28/drivers/usb/gadget/usbstring.c 2.08 KB
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  /*
   * 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/module.h>
  #include <linux/list.h>
  #include <linux/string.h>
  #include <linux/device.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];
  }
  EXPORT_SYMBOL_GPL(usb_gadget_get_string);