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 12:26:34 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, 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 Thu, May 16, 2024 at 12:22 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> 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.

Well, I prefer to cut a separate cleanup patch to make this more consistent.