1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * WMI string utility functions.
4 *
5 * Copyright (C) 2025 Armin Wolf <W_Armin@gmx.de>
6 */
7
8 #include <linux/build_bug.h>
9 #include <linux/compiler_types.h>
10 #include <linux/err.h>
11 #include <linux/export.h>
12 #include <linux/nls.h>
13 #include <linux/limits.h>
14 #include <linux/types.h>
15 #include <linux/wmi.h>
16
17 #include <asm/byteorder.h>
18
19 static_assert(sizeof(__le16) == sizeof(wchar_t));
20
21 /**
22 * wmi_string_to_utf8s - Convert a WMI string into a UTF8 string.
23 * @str: WMI string representation
24 * @dst: Buffer to fill with UTF8 characters
25 * @length: Length of the destination buffer
26 *
27 * Convert as WMI string into a standard UTF8 string. The conversion will stop
28 * once a NUL character is detected or when the buffer is full. Any invalid UTF16
29 * characters will be ignored. The resulting UTF8 string will always be NUL-terminated
30 * when this function returns successfully.
31 *
32 * Return: Length of the resulting UTF8 string or negative errno code on failure.
33 */
wmi_string_to_utf8s(const struct wmi_string * str,u8 * dst,size_t length)34 ssize_t wmi_string_to_utf8s(const struct wmi_string *str, u8 *dst, size_t length)
35 {
36 /* Contains the maximum number of UTF16 code points to read */
37 int inlen = le16_to_cpu(str->length) / 2;
38 int ret;
39
40 if (length < 1)
41 return -EINVAL;
42
43 /* We must leave room for the NUL character at the end of the destination buffer */
44 ret = utf16s_to_utf8s((__force const wchar_t *)str->chars, inlen, UTF16_LITTLE_ENDIAN, dst,
45 length - 1);
46 if (ret < 0)
47 return ret;
48
49 dst[ret] = '\0';
50
51 return ret;
52 }
53 EXPORT_SYMBOL_GPL(wmi_string_to_utf8s);
54
55 /**
56 * wmi_string_from_utf8s - Convert a UTF8 string into a WMI string.
57 * @str: WMI string representation
58 * @max_chars: Maximum number of UTF16 code points to store inside the WMI string
59 * @src: UTF8 string to convert
60 * @src_length: Length of the source string without any trailing NUL-characters
61 *
62 * Convert a UTF8 string into a WMI string. The conversion will stop when the WMI string is
63 * full. The resulting WMI string will always be NUL-terminated and have its length field set
64 * to and appropriate value when this function returns successfully.
65 *
66 * Return: Number of UTF16 code points inside the WMI string or negative errno code on failure.
67 */
wmi_string_from_utf8s(struct wmi_string * str,size_t max_chars,const u8 * src,size_t src_length)68 ssize_t wmi_string_from_utf8s(struct wmi_string *str, size_t max_chars, const u8 *src,
69 size_t src_length)
70 {
71 size_t str_length;
72 int ret;
73
74 if (max_chars < 1)
75 return -EINVAL;
76
77 /* We must leave room for the NUL character at the end of the WMI string */
78 ret = utf8s_to_utf16s(src, src_length, UTF16_LITTLE_ENDIAN, (__force wchar_t *)str->chars,
79 max_chars - 1);
80 if (ret < 0)
81 return ret;
82
83 str_length = (ret + 1) * sizeof(u16);
84 if (str_length > U16_MAX)
85 return -EOVERFLOW;
86
87 str->length = cpu_to_le16(str_length);
88 str->chars[ret] = '\0';
89
90 return ret;
91 }
92 EXPORT_SYMBOL_GPL(wmi_string_from_utf8s);
93