Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
platform/wmi: Add helper functions for WMI string conversions
WMI strings are encoded using UTF16-LE characters, forcing WMI drivers
to manually convert them to/from standard UTF8 strings. Add a two
helper functions for those tasks.
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://patch.msgid.link/20260116204116.4030-4-W_Armin@gmx.de
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
authored by
Armin Wolf
and committed by
Ilpo Järvinen
b990a06f
29dfba69
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-1
+3
Documentation/driver-api/wmi.rst
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Documentation/driver-api/wmi.rst
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drivers/platform/wmi/Kconfig
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drivers/platform/wmi/Kconfig
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-1
drivers/platform/wmi/Makefile
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-1
drivers/platform/wmi/Makefile
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drivers/platform/wmi/string.c
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drivers/platform/wmi/string.c
···
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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* WMI string utility functions.
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*
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* Copyright (C) 2025 Armin Wolf <W_Armin@gmx.de>
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*/
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#include <linux/build_bug.h>
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#include <linux/compiler_types.h>
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#include <linux/err.h>
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#include <linux/export.h>
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#include <linux/nls.h>
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#include <linux/limits.h>
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#include <linux/types.h>
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#include <linux/wmi.h>
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#include <asm/byteorder.h>
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static_assert(sizeof(__le16) == sizeof(wchar_t));
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/**
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* wmi_string_to_utf8s - Convert a WMI string into a UTF8 string.
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* @str: WMI string representation
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* @dst: Buffer to fill with UTF8 characters
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* @length: Length of the destination buffer
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*
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* Convert as WMI string into a standard UTF8 string. The conversion will stop
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* once a NUL character is detected or when the buffer is full. Any invalid UTF16
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* characters will be ignored. The resulting UTF8 string will always be NUL-terminated
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* when this function returns successfully.
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*
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* Return: Length of the resulting UTF8 string or negative errno code on failure.
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*/
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ssize_t wmi_string_to_utf8s(const struct wmi_string *str, u8 *dst, size_t length)
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{
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/* Contains the maximum number of UTF16 code points to read */
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int inlen = le16_to_cpu(str->length) / 2;
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int ret;
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if (length < 1)
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return -EINVAL;
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/* We must leave room for the NUL character at the end of the destination buffer */
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ret = utf16s_to_utf8s((__force const wchar_t *)str->chars, inlen, UTF16_LITTLE_ENDIAN, dst,
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length - 1);
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if (ret < 0)
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return ret;
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dst[ret] = '\0';
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return ret;
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}
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EXPORT_SYMBOL_GPL(wmi_string_to_utf8s);
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/**
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* wmi_string_from_utf8s - Convert a UTF8 string into a WMI string.
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* @str: WMI string representation
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* @max_chars: Maximum number of UTF16 code points to store inside the WMI string
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* @src: UTF8 string to convert
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* @src_length: Length of the source string without any trailing NUL-characters
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*
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* Convert a UTF8 string into a WMI string. The conversion will stop when the WMI string is
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* full. The resulting WMI string will always be NUL-terminated and have its length field set
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* to and appropriate value when this function returns successfully.
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*
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* Return: Number of UTF16 code points inside the WMI string or negative errno code on failure.
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*/
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ssize_t wmi_string_from_utf8s(struct wmi_string *str, size_t max_chars, const u8 *src,
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size_t src_length)
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{
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size_t str_length;
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int ret;
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if (max_chars < 1)
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return -EINVAL;
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/* We must leave room for the NUL character at the end of the WMI string */
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ret = utf8s_to_utf16s(src, src_length, UTF16_LITTLE_ENDIAN, (__force wchar_t *)str->chars,
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max_chars - 1);
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if (ret < 0)
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return ret;
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str_length = (ret + 1) * sizeof(u16);
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if (str_length > U16_MAX)
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return -EOVERFLOW;
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str->length = cpu_to_le16(str_length);
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str->chars[ret] = '\0';
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return ret;
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}
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EXPORT_SYMBOL_GPL(wmi_string_from_utf8s);
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include/linux/wmi.h
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include/linux/wmi.h
···
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__le16 chars[];
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} __packed;
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ssize_t wmi_string_to_utf8s(const struct wmi_string *str, u8 *dst, size_t length);
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ssize_t wmi_string_from_utf8s(struct wmi_string *str, size_t max_chars, const u8 *src,
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size_t src_length);
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int wmidev_invoke_method(struct wmi_device *wdev, u8 instance, u32 method_id,
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const struct wmi_buffer *in, struct wmi_buffer *out);
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