Re: [PATCH] platform/x86: huawei-wmi: add ACPI fallback for Fn-lock on newer models

[Ilpo Järvinen]

On Sun, 24 May 2026, Shaposhnikov Daniil wrote:

> Newer Huawei laptops (e.g. FLMH-XX / MateBook 14 2024) no longer support
> the legacy WMI interface for Fn-lock control. Instead, they expose direct
> ACPI methods \GFRS and \SFRS (Get/Set Fn key Reversal Status) which
> communicate with the EC via registers 0x6B (read) and 0x6C (write).
> 
> Add huawei_acpi_fn_lock_get() and huawei_acpi_fn_lock_set() helpers that
> use acpi_evaluate_object() to call these methods. Both
> huawei_wmi_fn_lock_get() and huawei_wmi_fn_lock_set() now probe for
> \GFRS/\SFRS via acpi_has_method() first and fall back to the legacy WMI
> path if not present.
> 
> Tested on: HUAWEI FLMH-XX (MateBook 14 2024),
> CachyOS (kernel 7.0.9-1-cachyos).
> 
> Signed-off-by: Shaposhnikov Daniil <2minesweeper2@xxxxxxxxx>
> ---
>  drivers/platform/x86/huawei-wmi.c | 95 +++++++++++++++++++++++++++++++
>  1 file changed, 95 insertions(+)
> 
> diff --git a/drivers/platform/x86/huawei-wmi.c b/drivers/platform/x86/huawei-wmi.c
> index 93cca17fdf58..19cd8f1a8e33 100644
> --- a/drivers/platform/x86/huawei-wmi.c
> +++ b/drivers/platform/x86/huawei-wmi.c
> @@ -527,11 +527,101 @@ static void huawei_wmi_battery_exit(struct device *dev)
>  
>  /* Fn lock */
>  
> +/*
> + * Newer Huawei models (e.g. HUAWEI FLMH-XX / MateBook 14 2024) use direct
> + * ACPI methods \GFRS / \SFRS (Get/Set Fn key Reversal Status) to control
> + * Fn-lock via EC registers 0x6B (read) and 0x6C (write).
> + *
> + * GFRS response buffer layout:
> + *   byte[0] = STAT (0 = success)
> + *   byte[1] = 0x01 (fn-lock off) or 0x02 (fn-lock on)
> + *
> + * SFRS argument layout (CreateByteField(Arg0, 0x02, FRSR)):
> + *   Value is read from byte[2] of the integer argument, so it must be
> + *   passed as (value << 16):
> + *   (1 << 16) = fn-lock off (writes 0x55 to EC 0x6C)
> + *   (2 << 16) = fn-lock on  (writes 0x5A to EC 0x6C)
> + */
> +
> +static int huawei_acpi_fn_lock_get(int *on)
> +{
> +	union acpi_object acpi_arg, *obj;
> +	struct acpi_object_list arg_list = { .count = 1, .pointer = &acpi_arg };
> +	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
> +	acpi_status status;
> +	u8 val;
> +
> +	acpi_arg.type = ACPI_TYPE_INTEGER;
> +	acpi_arg.integer.value = 0;
> +
> +	status = acpi_evaluate_object(NULL, "\\GFRS", &arg_list, &output);
> +	if (ACPI_FAILURE(status))
> +		return -EIO;
> +
> +	obj = output.pointer;

You must use __free() here to avoid duplicating kfree() (move the 
variable declaration mid-function).

> +	if (!obj || obj->type != ACPI_TYPE_BUFFER || obj->buffer.length < 2) {
> +		kfree(obj);
> +		return -ENODATA;
> +	}
> +
> +	/* byte[0] = STAT (0 = success), byte[1] = 1 (off) or 2 (on) */
> +	if (obj->buffer.pointer[0] != 0) {
> +		kfree(obj);
> +		return -EIO;
> +	}
> +
> +	val = obj->buffer.pointer[1];
> +	if (val != 1 && val != 2) {

These magic literals should be replaced with using named defines.

> +		kfree(obj);
> +		return -ENODATA;
> +	}
> +
> +	if (on)
> +		*on = val - 1; /* 1→0 (off), 2→1 (on) */

This too is unnecessarily cryptic (on a non-performance critical path).

One option would be to convert these two if blocks into a single 
switch/case. You need to duplicate the if (on) to both case blocks but 
that doesn't look too bad.

> +
> +	kfree(obj);
> +	return 0;
> +}
> +
> +static int huawei_acpi_fn_lock_set(int on)
> +{
> +	union acpi_object acpi_arg, *obj;
> +	struct acpi_object_list arg_list = { .count = 1, .pointer = &acpi_arg };
> +	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
> +	acpi_status status;
> +	int ret = 0;
> +
> +	/*
> +	 * SFRS reads byte[2] of its argument via CreateByteField(Arg0, 0x02).
> +	 * on=0 → FRSR=1 → EC gets 0x55 (fn-lock off)
> +	 * on=1 → FRSR=2 → EC gets 0x5A (fn-lock on)
> +	 */
> +	acpi_arg.type = ACPI_TYPE_INTEGER;
> +	acpi_arg.integer.value = (u64)(on + 1) << 16;

Please make a named define instead.

The cast looks unnecessary.

> +
> +	status = acpi_evaluate_object(NULL, "\\SFRS", &arg_list, &output);
> +	if (ACPI_FAILURE(status))
> +		return -EIO;
> +
> +	obj = output.pointer;

As with above, please use __free()...

> +	if (obj && obj->type == ACPI_TYPE_BUFFER &&
> +	    obj->buffer.length >= 1 && obj->buffer.pointer[0] != 0)
> +		ret = -EIO;

...This can then return immediately.

> +
> +	kfree(obj);
> +	return ret;
> +}
> +
>  static int huawei_wmi_fn_lock_get(int *on)
>  {
>  	u8 ret[0x100] = { 0 };
>  	int err, i;
>  
> +	/* Newer models: use direct ACPI \GFRS method */
> +	if (acpi_has_method(NULL, "\\GFRS"))
> +		return huawei_acpi_fn_lock_get(on);
> +
> +	/* Legacy WMI fallback */
>  	err = huawei_wmi_cmd(FN_LOCK_GET, ret, 0x100);
>  	if (err)
>  		return err;
> @@ -550,6 +640,11 @@ static int huawei_wmi_fn_lock_set(int on)
>  {
>  	union hwmi_arg arg;
>  
> +	/* Newer models: use direct ACPI \SFRS method */
> +	if (acpi_has_method(NULL, "\\SFRS"))
> +		return huawei_acpi_fn_lock_set(on);
> +
> +	/* Legacy WMI fallback */
>  	arg.cmd = FN_LOCK_SET;
>  	arg.args[2] = on + 1; // 0 undefined, 1 off, 2 on.
>  
> 

-- 
 i.