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Date: Mon, 06 Nov 2000 16:15:36 +0100
From: Martin Dalecki <dalecki@evision-ventures.com>
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To: David Woodhouse <dwmw2@infradead.org>
CC: Jeff Garzik <jgarzik@mandrakesoft.com>, Dan Hollis <goemon@anime.net>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Oliver Xymoron <oxymoron@waste.org>, Keith Owens <kaos@ocs.com.au>,
        linux-kernel@vger.kernel.org
Subject: Re: Persistent module storage [was Linux 2.4 Status / TODO page]
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David Woodhouse wrote:
> 
> jgarzik@mandrakesoft.com said:
> >  * Driver initializes mixer to 100% muted * Userspace app sets desired
> > values to /dev/mixer * Userspace app opens /dev/dsp to play sound
> 
> > I don't see where any sound can "escape" in this scenario, and it
> > doesn't require any module data persistence...
> 
> * User boots kernel
> * User loads mixer app
> * Sound module is autoloaded, defaults to zero levels. This is fine.
> * User sets 'line in' level to appropriate level to listen to radio
> * User closes mixer app
> * Time passes
> * Sound module is unloaded
> * User continues to happily listen to radio through sound card
> * Time passes
> * User is listening intently to something on the radio
> * Something wants to beep through /dev/audio
> * Sound module is autoloaded again, default to zero levels.
>         This time it is _NOT_ fine. User is rightly pissed off :)
> 
> It's fine to default to zero levels the first time the sound module is
> loaded after booting. Not on subsequent reloads though.
> 
> A long time ago, I made the sb16 driver use the persistent storage facility
> of kerneld to store mixer levels. I was happy with this right up until
> kerneld disappeared :)

It was removed for good reasons.

> I then made a version which read the current mixer levels back from the
> hardware on initialisation, and didn't reset them. That didn't work on all
> sb16 hardware, but it worked for me (tm).
> 
> Persistent storage is the best way to do it though. It doesn't have to be
> persistent over reboots, just during the lifetime of the kernel.

No! The best way to do it are just *persistently loaded* modules.
It's THAT simple!
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