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Date:      Mon, 14 Dec 1998 23:49:37 -0700
From:      Warner Losh <imp@village.org>
To:        Mike Smith <mike@smith.net.au>
Cc:        current@FreeBSD.ORG
Subject:   Re: PAO Integration? 
Message-ID:  <199812150649.XAA02978@harmony.village.org>
In-Reply-To: Your message of "Sun, 13 Dec 1998 15:21:25 PST." <199812132321.PAA00350@dingo.cdrom.com> 
References:  <199812132321.PAA00350@dingo.cdrom.com>  

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In message <199812132321.PAA00350@dingo.cdrom.com> Mike Smith writes:
: Drivers should export a set of options that are a union of the set of 
: options the driver supports plus a subset of the options for a device 
: provided by the bus.  This can be determined by examining the driver 
: and bus data at probe/attach time; something that's easy with KLD/
: newbus/loader, but would require a bolt-on for newconfig.

A sysctl-like mechanism would likely be a good idea.  Let me explain
what I have in mind.

First, let us say that there are configuration files.  Let us say
these files use the sysctl syntax.  Let us further suppose that we
extend the sysctl notation to include wild cards.  We'd have something
similar to the xdefaults (xrdb actually) syntax.  This sparse database
would be kept around.

When modules are initialized (either as being part of the base system,
statically linked in, or when dynamically loaded by some means), the
sysctl's variables are set (if they match this sparse database).

Now, this would allow drivers and other modules to be dynamically
configured in a user friendly manner.  The "sparse database" would
allow for the user to specify things (eg the band for a radio modem,
the video signalling to use (ntsc vs pal), etc).

Some examples:

driver.aha*tune_bus: 1
driver.bt848*video_format: ntsc

When the aha driver starts, it registers the sysctl variable

driver.aha.unit0.tune_bus

and then finds its value.  Since it matchces the above sepecification,
it will have a value of 1 when the driver checks its value.

This would allow a very easy way to configure and customize the
modules that are loaded and unloaded.

Comments?

Warner

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