linux-kernel - New sysfs interface for privacy screens

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Message-ID: <CAL_quvRknSSVvXN3q_Se0hrziw2oTNS3ENNoeHYhvciCRq9Yww@mail.gmail.com>
Date:   Tue, 1 Oct 2019 10:09:46 -0600
From:   Mat King <mathewk@...gle.com>
To:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Cc:     gregkh@...uxfoundation.org, rafael@...nel.org,
        Ross Zwisler <zwisler@...gle.com>,
        Rajat Jain <rajatja@...gle.com>,
        Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>
Subject: New sysfs interface for privacy screens

Resending in plain text mode

I have been looking into adding Linux support for electronic privacy
screens which is a feature on some new laptops which is built into the
display and allows users to turn it on instead of needing to use a
physical privacy filter. In discussions with my colleagues the idea of
using either /sys/class/backlight or /sys/class/leds but this new
feature does not seem to quite fit into either of those classes.

I am proposing adding a class called "privacy_screen" to interface
with these devices. The initial API would be simple just a single
property called "privacy_state" which when set to 1 would mean that
privacy is enabled and 0 when privacy is disabled.

Current known use cases will use ACPI _DSM in order to interface with
the privacy screens, but this class would allow device driver authors
to use other interfaces as well.

Example:

# get privacy screen state
cat /sys/class/privacy_screen/cros_privacy/privacy_state # 1: privacy
enabled 0: privacy disabled

# set privacy enabled
echo 1 > /sys/class/privacy_screen/cros_privacy/privacy_state

 Does this approach seem to be reasonable?