I don't know of any specific documentation, but it's pretty easy:
Devices, any kind of device, can export a match, based on specific
properties of the subsystem it belongs to. In most cases its the same
propery/id that is used inside the kernel, to find a (already loaded)
driver which will bind this device.
Any unique string, hardware ID's, whatever, are stuffed into a modalias,
prefixed by "<subsystem>:" to be unique.
PCI and USB are pretty obvious, they just stuff all their hardware ID'S
into a string, in a defined order, and let every device export that value
to userspace by MODALIAS environment key and the "modalias" sysfs file.
Other subsystem may have simple strings to match, they define
themselves.
Now, the drivers contain "match id tables" which are used by the core
to bind devices to drivers. These tables area made available to
file2alias.c in the module postprocessing, and will end up in the
module file itself. The string is mangled to contain wildcards, so
they can just be fnmatch()'d against the modalias value, which the
devices export.
The string embedded in the modules are extracted by depmod, and put
into the modules.aliases file in /lib/modules/. Every time modprobe
is called with an alias, it searches through this file and loads all
modules which contained a matching alias string.
Udev does nothing but stupidly running modprobe for every device which
contains MODALIAS in the event environment, and passes $MODALIAS as
an argument to modprobe.
Only if we change the format of the current pnp device aliases
to something like:
pnp*:XYZ2324:*
pnp*:ABC1234:*
and create a "modalias" file at every pnp device, and add MODALIAS to
the uevent. The modalias must contains all ID's which belong to that
device in one single string, separated and terminated by a special
character, something like:
pnp:ABC1234:XYZ2324:RST3445:
That's how acpi should work with this patch now.
Kay
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