$MODALIAS and platform_bus ...

[David Brownell <david-b@pacbell.net>]

Has anyone done anything to make sure platform_bus devices can
use this new $MODALIAS infrastructure?  I was looking at the
implications for "coldplug" processing, and there's a hole
where platform device support would go.

As a reminder, those devices don't do driver binding quite the
normal way.  They more or less use the rule that the driver
name and device name must match (modulo optional numeric suffix
on the device).  System-on-Chip processors use platform_bus for
most of the on-chip peripherals ... potentially dozens of them,
but any given board probably won't wire them all up.

So given a /sys/devices/platform/$NAME/. there are a few things
standing in the way of automatically initializing those devices:

 - No /sys/devices/platform/$NAME/modalias
 - No MODULE_ALIAS(...) in the driver module

Now the former would seem easy to provide, or even eliminate
the requirement for it ... the "modalias" will either be $NAME
or $NAME less a prefix such as ".1" or ".2".  Or, it should be
trivial to have linux/drivers/bus/platform.c create it.

The latter would seem just a bit trickier, since it couldn't
be driven using linux/scripts/mod/file2alias.c because that
relies on a non-existent module device table.  Drivers could
explicitly write MODULE_ALIAS if their module name didn't
already match that convention, but that could be quite a lot
of drivers to change.

Comments? 

- Dave


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