Received-SPF: pass (google.com: domain of linux-kernel+bounces-176024-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Precedence: bulk
MIME-Version: 1.0
References: <5787281.DvuYhMxLoT@kreacher> <4926735.31r3eYUQgx@kreacher> <ac04c433-b0ac-4b82-b8eb-98ac16f872d8@gmx.de>
In-Reply-To: <ac04c433-b0ac-4b82-b8eb-98ac16f872d8@gmx.de>
From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Fri, 10 May 2024 18:41:48 +0200
Message-ID: <CAJZ5v0g_NjGHRvhm-N5vQFnOsqnxExSq99v8n_B_6ANoaCga0w@mail.gmail.com>
Subject: Re: [PATCH v1 1/2] ACPI: EC: Install address space handler at the
 namespace root
To: Armin Wolf <W_Armin@gmx.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>, Linux ACPI <linux-acpi@vger.kernel.org>, 
	LKML <linux-kernel@vger.kernel.org>, 
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Hans de Goede <hdegoede@redhat.com>, 
	Mario Limonciello <mario.limonciello@amd.com>, 
	Heikki Krogerus <heikki.krogerus@linux.intel.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Fri, May 10, 2024 at 6:10=E2=80=AFPM Armin Wolf <W_Armin@gmx.de> wrote:
>
> Am 10.05.24 um 16:03 schrieb Rafael J. Wysocki:
>
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.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) [Embedded=
Control] (20230628/evregion-130)
> >
> > This happens because 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.
> >
> > 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.
>
> Hi,
>
> the patch itself looks good to me, but i wonder what happens if multiple
> ACPI EC devices are present. How would we handle such a situation?

I'm wondering if this is a theoretical question or do you have any
existing or planned systems in mind?

ec_read(), ec_write() and ec_transaction() use only the first EC that
has been found anyway.