linux-kernel - Re: [PATCH v2 1/2] ACPI: EC: Install address space handler at the namespace root

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Date: Thu, 16 May 2024 13:22:35 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Linux ACPI <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Mario Limonciello <mario.limonciello@....com>,
	Armin Wolf <w_armin@....de>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH v2 1/2] ACPI: EC: Install address space handler at the
 namespace root

On Wed, May 15, 2024 at 09:40:54PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> It is reported that _DSM evaluation fails in ucsi_acpi_dsm() on Lenovo
> IdeaPad Pro 5 due to a missing address space handler for the EC address
> space:
> 
>  ACPI Error: No handler for Region [ECSI] (000000007b8176ee) [EmbeddedControl] (20230628/evregion-130)
> 
> This happens because if there is no ECDT, the EC driver only registers
> the EC address space handler for operation regions defined in the EC
> device scope of the ACPI namespace while the operation region being
> accessed by the _DSM in question is located beyond that scope.
> 
> To address this, modify the ACPI EC driver to install the EC address
> space handler at the root of the ACPI namespace for the first EC that
> can be found regardless of whether or not an ECDT is present.
> 
> Note that this change is consistent with some examples in the ACPI
> specification in which EC operation regions located outside the EC
> device scope are used (for example, see Section 9.17.15 in ACPI 6.5),
> so the current behavior of the EC driver is arguably questionable.

..

> -		status = acpi_install_address_space_handler_no_reg(ec->handle,
> +		status = acpi_install_address_space_handler_no_reg(scope_handle,
>  								   ACPI_ADR_SPACE_EC,
>  								   &acpi_ec_space_handler,
>  								   NULL, ec);

Looking at this...

>  		if (ACPI_FAILURE(acpi_remove_address_space_handler(
> +						scope_handle,
> +						ACPI_ADR_SPACE_EC,
> +						&acpi_ec_space_handler)))

..and this, I believe you can move scope_handle to the previous line and align
the rest for the sake of consistency and slightly better readability.

-- 
With Best Regards,
Andy Shevchenko