Re: [PATCH] Add MPC5200B base board mvBC-P

["Grant Likely" <grant.likely@secretlab.ca>]

On Mon, Jul 7, 2008 at 1:49 AM, Andre Schwarz
<andre.schwarz@matrix-vision.de> wrote:
> David,
>
> thanks - removed "device_type" from the DMA controller.
>
> Which nodes actually require "device_type" and which don't ?
>
> Is there some general rule ?

Segher, David;

In OF, what is the purpose of device_type?  From what I understand
right now, each value of device_type claims a software interface that
the device supports.  So for example, device_type = "serial" means
that firmware supports using the device as a serial port, correct?
So, similarly, if OF did not have a driver for the device, then the
presence a device_type property would be a bug, right?

Does device_type indicated any other information other than firmware
driver interface?

I had an epiphany about device_type this weekend (and by epiphany, I
mean realizing my own stupidity).  If I'm correct about the above
questions, then that would mean it is *always* a bug to have a
device_type property in .dts file because there is no firmware
interface.  So, it seems to me that we shouldn't just be eliminating
undefined device_type values, but also eliminate the ones that are
defined in OF because .dts users do not support the firmware driver
interface.

Am I correct?

The only situation where I can see it being appropriate to specify
device_type is to work around older bindings that are ambiguous with
their other properties.

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.