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From:   Nick Crews <ncrews@chromium.org>
Date:   Tue, 9 Apr 2019 14:46:55 -0600
Message-ID: <CAHX4x87OcNofMLQTWJJR1NgaDQ=xT3MQpTv6pzkViyTbZwwKgw@mail.gmail.com>
Subject: Re: [PATCH v3] platform/chrome: Add Wilco EC Event Handling
To:     Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Benson Leung <bleung@chromium.org>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Duncan Laurie <dlaurie@chromium.org>,
        Oleh Lamzin <lamzin@google.com>,
        Bartosz Fabianowski <bartfab@google.com>,
        Guenter Roeck <groeck@google.com>,
        Dmitry Torokhov <dtor@google.com>
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Hi!

I know people had questions with the structure/uses of the events in the
previous versions of this patch. Does this clear things up?

Thanks, Nick

On Wed, Apr 3, 2019 at 6:31 PM Nick Crews <ncrews@chromium.org> wrote:
>
> The Wilco Embedded Controller can create custom events that
> are not handled as standard ACPI objects. These events can
> contain information about changes in EC controlled features,
> such as errors and events in the dock or display. For example,
> an event is triggered if the dock is plugged into a display
> incorrectly. These events are needed for telemetry and
> diagnostics reasons, and for possibly alerting the user.
>
> These events are triggered by the EC with an ACPI Notify(0x90),
> and then the BIOS reads the event buffer from EC RAM via an
> ACPI method. When the OS receives these events via ACPI,
> it passes them along to this driver. The events are put into
> a queue which can be read by a userspace daemon via a char device
> that implements read() and poll(). The char device will appear at
> /dev/wilco_event{n}, where n is some small non-negative integer,
> starting from 0. Standard ACPI events such as the battery getting
> plugged/unplugged can also come through this path, but they are
> dealt with via other paths, and are ignored here.
>
> To test, you can tail the binary data with
> $ cat /dev/wilco_event0 | hexdump -ve '1/1 "%x\n"'
> and then create an event by pressing fn+Esc.
>
> v3 changes:
> - Made commit description more accurate and useful.
> - Added an exclusive lock for opening the char device,
>   so only one userspace process can read events at a time.
>
> Signed-off-by: Nick Crews <ncrews@chromium.org>