linux-kernel - Re: New sysfs interface for privacy screens

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Date:   Tue, 1 Oct 2019 18:27:10 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mat King <mathewk@...gle.com>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.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: Re: New sysfs interface for privacy screens

On Tue, Oct 01, 2019 at 10:09:46AM -0600, Mat King wrote:
> 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

What is "cros_privacy" here?

>  Does this approach seem to be reasonable?

Seems sane to me, do you have any code that implements this so we can
see it?

thanks,

greg k-h