cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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usbstring.c (2437B)

      1// SPDX-License-Identifier: LGPL-2.1+
      2/*
      3 * Copyright (C) 2003 David Brownell
      4 */
      5
      6#include <linux/errno.h>
      7#include <linux/kernel.h>
      8#include <linux/module.h>
      9#include <linux/list.h>
     10#include <linux/string.h>
     11#include <linux/device.h>
     12#include <linux/nls.h>
     13
     14#include <linux/usb/ch9.h>
     15#include <linux/usb/gadget.h>
     16
     17
     18/**
     19 * usb_gadget_get_string - fill out a string descriptor 
     20 * @table: of c strings encoded using UTF-8
     21 * @id: string id, from low byte of wValue in get string descriptor
     22 * @buf: at least 256 bytes, must be 16-bit aligned
     23 *
     24 * Finds the UTF-8 string matching the ID, and converts it into a
     25 * string descriptor in utf16-le.
     26 * Returns length of descriptor (always even) or negative errno
     27 *
     28 * If your driver needs stings in multiple languages, you'll probably
     29 * "switch (wIndex) { ... }"  in your ep0 string descriptor logic,
     30 * using this routine after choosing which set of UTF-8 strings to use.
     31 * Note that US-ASCII is a strict subset of UTF-8; any string bytes with
     32 * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
     33 * characters (which are also widely used in C strings).
     34 */
     35int
     36usb_gadget_get_string (const struct usb_gadget_strings *table, int id, u8 *buf)
     37{
     38	struct usb_string	*s;
     39	int			len;
     40
     41	/* descriptor 0 has the language id */
     42	if (id == 0) {
     43		buf [0] = 4;
     44		buf [1] = USB_DT_STRING;
     45		buf [2] = (u8) table->language;
     46		buf [3] = (u8) (table->language >> 8);
     47		return 4;
     48	}
     49	for (s = table->strings; s && s->s; s++)
     50		if (s->id == id)
     51			break;
     52
     53	/* unrecognized: stall. */
     54	if (!s || !s->s)
     55		return -EINVAL;
     56
     57	/* string descriptors have length, tag, then UTF16-LE text */
     58	len = min((size_t)USB_MAX_STRING_LEN, strlen(s->s));
     59	len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
     60			(wchar_t *) &buf[2], USB_MAX_STRING_LEN);
     61	if (len < 0)
     62		return -EINVAL;
     63	buf [0] = (len + 1) * 2;
     64	buf [1] = USB_DT_STRING;
     65	return buf [0];
     66}
     67EXPORT_SYMBOL_GPL(usb_gadget_get_string);
     68
     69/**
     70 * usb_validate_langid - validate usb language identifiers
     71 * @langid: usb language identifier
     72 *
     73 * Returns true for valid language identifier, otherwise false.
     74 */
     75bool usb_validate_langid(u16 langid)
     76{
     77	u16 primary_lang = langid & 0x3ff;	/* bit [9:0] */
     78	u16 sub_lang = langid >> 10;		/* bit [15:10] */
     79
     80	switch (primary_lang) {
     81	case 0:
     82	case 0x62 ... 0xfe:
     83	case 0x100 ... 0x3ff:
     84		return false;
     85	}
     86	if (!sub_lang)
     87		return false;
     88
     89	return true;
     90}
     91EXPORT_SYMBOL_GPL(usb_validate_langid);