linux-kernel - Re: [PATCH linux-next] tty: Disable default console blanking interval

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Date:   Thu, 23 Mar 2017 03:06:52 +0100
From:   Adam Borowski <kilobyte@...band.pl>
To:     Tim Gardner <tim.gardner@...onical.com>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Scot Doyle <lkml14@...tdoyle.com>
Subject: Re: [PATCH linux-next] tty: Disable default console blanking interval

On Wed, Mar 22, 2017 at 07:50:32AM -0600, Tim Gardner wrote:
> BugLink: http://bugs.launchpad.net/bugs/869017
> 
> I'm not particularly knowledgable about console issues. Is a blaknking interval
> relevant in a post CRT world ? The argument in the bug description seems
> compelling.

I have no direct knowledge about screen burn-in, but a quick search shows
that, while not as prevalent as in the CRT days, it's still an issue:
https://en.wikipedia.org/wiki/Screen_burn-in
https://encrypted.google.com/search?hl=en&q=lcd%20screen%20burn-in

> -static int blankinterval = 10*60;
> +static int blankinterval;

Thus, the current default might be safer: an even all-black image will keep
the display readable as there won't be any localized artefacts.  On the
other hand, the photos I see are nowhere as bad as it was the case on CRTs,
so this reason might be dismissed.

There is another concern, though: light pollution.  A white image makes the
room bright enough to read by.  Don't laugh but 20 years ago in the dorm I
used to print \e[37;47;1m then 2000 'X'es to the screen to do things[1] (the
overhead light would wake up the roommates).  That was a CRT, LCDs are
brighter.  Obviously, lightgrey text on a black background producess less
light than all-white, but a regular monitor probably still gives off a total
amount of light similar to that of an all-white smartphone.

I'm not sure how many non-X screens are placed in rooms where someone tries
to sleep, but it's not something to ignore entirely.

I'm not arguing a hard "no", but you should at least think of the above two
concerns.

[1]. Not reading obviously, I am not _that_ insane. :þ
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