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 | */ |
35 | int |
36 | usb_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->s, len, endian: UTF16_LITTLE_ENDIAN, |
60 | pwcs: (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 | } |
67 | EXPORT_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 | */ |
75 | bool 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 | } |
91 | EXPORT_SYMBOL_GPL(usb_validate_langid); |
92 | |