On Mon, Nov 19, 2012 at 03:49:25PM -0700, Bjorn Helgaas wrote:

I think the benefit here is that you can merely point
.acpi_match_table at an acpi_device_id[] table, then use
platform_get_resource() as a generic way to get resources, whether the
platform device came from OF, ACPI, etc.  The alternative would be to
add, e.g., a PNP driver with a .probe() method that uses
pnp_get_resource().  That's not very much code, but it is more, even
if the .probe() method just calls a device registration function
that's shared across bus types.

That benefit seems like a great thing, and my question then is why
wouldn't we just do it across the board and make platform devices for
*all* ACPI devices without having the I2C and SPI special cases?

That wouldn't be any better than having a PNP or ACPI device. We must still
create the corresponding I2C or SPI device in order to have a driver that
can plug into I2C or SPI core.