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Date:      Wed, 25 Jul 2001 13:18:35 -0700 (PDT)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>
Cc:        freebsd-current@freebsd.org
Subject:   RE: Death sentence to KLD screen savers? Comments?
Message-ID:  <XFMail.010725131835.jhb@FreeBSD.org>
In-Reply-To: <200107241207.VAA14339@zodiac.mech.utsunomiya-u.ac.jp>

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On 24-Jul-01 Kazutaka YOKOTA wrote:
> This is to propose to abolish KLD screen saver modules.
> 
> KLD screen savers have the following problems/deficiencies.
> 
> - It is too easy to abuse the power of being run in the kernel
>   mode. The screen saver is invoked periodically once the console
>   becomes idle. It should not spend long time to draw something
>   to the screen. But, we may be tempted to do a bit more elaborate
>   drawing so that we get "interesting" effects. It's too easy to
>   degrade the system performance by staying in the screen saver 
>   too long.

You can stick the screen saver in a low priority kthread and achieve the same
effect.

> - While it is easy to manipulate the video board in the KLD module
>   (because we can go anywhere and access anything :-), there are
>   limitations. If you want to perform file I/O (to obtain some
>   bitmaps from files), or want to read some sort of configuration
>   file, there is no straight forward way to do so.

You can use kldload or the loader with the -t 'foo' stuff to load configuration
files, etc. that modules can get at.

Just pointing out that userland is not the only way of achieving your goals.

-- 

John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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