On Thu, Mar 10, 2011 at 03:29:25PM +0100, Arnd Bergmann wrote:

On Thursday 10 March 2011, Mark Brown wrote:

quoted

Lots of stuff (like the MFD children of I2C devices) gets shoved on the
platform bus on Linux - every time someone considers creating a new bus
type for trivial devices the discussion ends up saying that the code
will end up being pretty much identical to the platform bus as it's so
straightforward so there's no point in cut'n'pasting the code.

Note that there is a difference between using top-level platform
devices (the ones that show up in /sys/devices/platform/) and platform
devices that are children of others (all the others that are in
/sys/bus/platform).

Sure.

What some broken drivers do is to create platform devices ad hoc
and just put them into /sys/platform/ directly although the
devices clearly have a parent somewhere. These are bugs that should
be fixed.

Most of the devices doing that on ARMs tend to be devices where there's
no bus that it's meaningful to expose to software - they'll typically be
hanging off an AHB or APB bus which has either no real software control
or control which is very heavily tied into the overall system control
and so is better treated over the whole SoC rather than the bus.