linux-kernel - Re: [PATCH v2 1/2] platform/x86: wmi: Support reading/writing 16 bit EC values

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Date: Fri, 8 Mar 2024 10:01:05 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Armin Wolf <W_Armin@....de>
cc: Hans de Goede <hdegoede@...hat.com>, 
    "Rafael J. Wysocki" <rafael@...nel.org>, lenb@...nel.org, 
    linux-acpi@...r.kernel.org, platform-driver-x86@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] platform/x86: wmi: Support reading/writing 16
 bit EC values

On Thu, 7 Mar 2024, Armin Wolf wrote:

> The ACPI EC address space handler currently only supports
> reading/writing 8 bit values. Some firmware implementations however
> want to access for example 16 bit values, which is prefectly legal
> according to the ACPI spec.
> 
> Add support for reading/writing such values.
> 
> Tested on a Dell Inspiron 3505 and a Asus Prime B650-Plus.
> 
> Signed-off-by: Armin Wolf <W_Armin@....de>

> @@ -1162,27 +1188,28 @@ acpi_wmi_ec_space_handler(u32 function, acpi_physical_address address,
>  			  u32 bits, u64 *value,
>  			  void *handler_context, void *region_context)
>  {
> -	int result = 0;
> -	u8 temp = 0;
> +	int bytes = bits / BITS_PER_BYTE;
> +	int ret;
> +
> +	if (!value)
> +		return AE_NULL_ENTRY;
> 
> -	if ((address > 0xFF) || !value)
> +	if (bytes > sizeof(*value))
>  		return AE_BAD_PARAMETER;
> 
> -	if (function != ACPI_READ && function != ACPI_WRITE)
> +	if (address > U8_MAX || address + bytes > U8_MAX)

This doesn't look correct. With address = 0xff and bits = 8 this will 
return AE_BAD_PARAMETER, is that intensional?

-- 
 i.