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// SPDX-License-Identifier: LGPL-2.1+
/*
* Copyright (C) 2003 David Brownell
*/
#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 (const 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)USB_MAX_STRING_LEN, strlen(s->s));
len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
(wchar_t *) &buf[2], USB_MAX_STRING_LEN);
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);
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