linux-kernel - Re: [PATCH] ACPI: EC: Relax sanity check of the ECDT ID string

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Message-ID: <e911ca96-fe8f-4cc5-bf68-f20ec7da46be@0upti.me>
Date: Tue, 29 Jul 2025 10:00:50 +0300
From: Ilya K <me@...ti.me>
To: Armin Wolf <W_Armin@....de>, rafael@...nel.org, lenb@...nel.org
Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: EC: Relax sanity check of the ECDT ID string

On 2025-07-29 09:20, Armin Wolf wrote:
> It turns out that the ECDT table inside the ThinkBook 14 G7 IML
> contains a valid EC description but an invalid ID string
> ("_SB.PC00.LPCB.EC0"). Ignoring this ECDT based on the invalid
> ID string prevents the kernel from detecting the built-in touchpad,
> so relax the sanity check of the ID string and only reject ECDTs
> with empty ID strings.
> 
> Compile-tested only.
> 
> Reported-by: Ilya K <me@...ti.me>
> Fixes: 7a0d59f6a913 ("ACPI: EC: Ignore ECDT tables with an invalid ID string")
> Signed-off-by: Armin Wolf <W_Armin@....de>
> ---
>  drivers/acpi/ec.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 

Thanks, this works!

Tested-by: Ilya K <me@...ti.me>

> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
> index 75c7db8b156a..7855bbf752b1 100644
> --- a/drivers/acpi/ec.c
> +++ b/drivers/acpi/ec.c
> @@ -2033,7 +2033,7 @@ void __init acpi_ec_ecdt_probe(void)
>  		goto out;
>  	}
>  
> -	if (!strstarts(ecdt_ptr->id, "\\")) {
> +	if (!strlen(ecdt_ptr->id)) {
>  		/*
>  		 * The ECDT table on some MSI notebooks contains invalid data, together
>  		 * with an empty ID string ("").
> @@ -2042,9 +2042,13 @@ void __init acpi_ec_ecdt_probe(void)
>  		 * a "fully qualified reference to the (...) embedded controller device",
>  		 * so this string always has to start with a backslash.
>  		 *
> -		 * By verifying this we can avoid such faulty ECDT tables in a safe way.
> +		 * However some ThinkBook machines have a ECDT table with a valid EC
> +		 * description but an invalid ID string ("_SB.PC00.LPCB.EC0").
> +		 *
> +		 * Because of this we only check if the ID string is empty in order to
> +		 * avoid the obvious cases.
>  		 */
> -		pr_err(FW_BUG "Ignoring ECDT due to invalid ID string \"%s\"\n", ecdt_ptr->id);
> +		pr_err(FW_BUG "Ignoring ECDT due to empty ID string\n");
>  		goto out;
>  	}
>  

Would it maybe make sense to also log a warning for the old case? Maybe a vendor will notice it and fix the firmware...
(yeah yeah fat chance)