sbc: isa plug-n-play

Torfinn Ingolfsen torfinn.ingolfsen at
Fri Feb 22 17:00:45 UTC 2008

On Fri, 22 Feb 2008 18:17:27 +0200
Andriy Gapon <avg at> wrote:

> Everything works great. But recently I had an itch to go trough BIOS
> settings. I spotted one named "Plug-n-Play OS" and it was set to

The BIOS setting "Plug and Play OS" usually means that the OS will do
its own little dance to set up any devices, so the bios just leaves
them alone.

> After that no joy, the soundcard stopped to work. It was detected as
> before, there is no difference in dmesg whatsoever, but it did not

Are you sure that it was detected _exactly_ as before? With the same
irq(s), dma channels and so on?

> So I disabled the option again and everything is fine.
> Practical conclusion: don't do it.
> Question of curiosity: what is it that BIOS can do with this card that
> our driver can not ?

Well, the bios (and acpi on systems that have it) set up devices by
assigning them irqs, io, memory and whatnot, if I undertstand this

My understanding is that FreeBSD uses this information to attach drivers
to the devices. If the devices are not set up correctly, FreeBSD either
might not find them or it can't use them correctly.
Torfinn Ingolfsen

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