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 */ 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 */ 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