New sysfs interface for privacy screens

[Mat King]

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?