Subject: Re: ISA direct config of ACPI devices
To: Jared D. McNeill <>
From: Matthias Drochner <>
List: tech-kern
Date: 11/22/2007 17:53:53 said:
> Any suggestions? "dev/isa/acpidevs" seemed a bit out of place... 

Well, "acpi-isadevs" perhaps...

After sleeping over this, I'd say it would be better to do it
differently. While attaching acpi devices at isa solves the
immediate problem with reserved unit numbers, it is a step
into the wrong direction. In the long term, we should be able
to run a system without an ISA bus configured at all. That's
why I'd say we should keep these devices attaching at acpi,
but somehow work around the reserved unit numbers.

The problem is of course how to do this without making a mess
of the autoconf system.

I can imagine 3 approaches:
a) "steal" the unit numbers from isa: If an acpi node is found,
   and NISA>0, call a special function within the isa code which
   tells if an FSTATE_NOTFOUND entry exists, makes it FOUND and
   returns the unit number for use by the acpi attachment.
b) Defer potential isa devices:
   If an acpi node is found, use some heuristic (address range
   based, or a table of pnp IDs) which tells whether it could be
   an ISA device. In that case, put it onto a waiting list.
   After ISA configuration, come back to that list and attach
   the devices which were not handled by isa.
c) Use some pseudo-bus (an interface attribute in terms of the
   autoconf system) which abstracts from the ISA semantics.
   (There is some "isabus" attribute already which could do it
   perhaps, but it would have to be checked.)
   Both the "isa" bus and "acpi" would carry that attribute,
   and the com etc devices would have that attribute as parent
   in the kernel config file.
   If an acpi node is found, first a config_found() with the
   isa-like attribute is tried, and if this doesn't attach
   anything the standard acpi call is done.

I like (c) most because it looks least hackish. Details
need to be checked.

best regards

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