68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
// 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) 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);
|