RFC: Rev 0.5 Booting the Linux/ppc kernel without Open Firmware

[Kumar Gala]

On Tue, 20 Dec 2005, Arnd Bergmann wrote:

> On Maandag 19 Dezember 2005 21:49, Kumar Gala wrote:
> > I'm still in favor of just leaving these devices as straight platform 
> > devices.  Unless there is something that is bus specific that each device 
> > on the bus conforms to I dont see any reason to create a new bus type.
> 
> How do platform devices work with module autoloading? What I'm interested
> in is to have stuff like the Fedora installer or kernels with modular
> drivers 'just work' because they can use the same way to load their
> modules that is already used for PCI devices.
> 
> AFAICS, that requires at least two things:
> - The device needs to be created when the bus is probed, i.e.
>   of_device_register can not be called from inside the driver
>   module_init() function.
> 

This is already handled by the platform device in the kernel.

> - The bus type needs to create a modalias file so user space can
>   do the matching with the of device table in the modules.

Seems like a simple thing to add to platform device.
 
> Both of these should be a lot easier to implement with a special
> bus type that creates entries in sysfs for a subset of the OF
> device tree.

I still dont see what a new bus type get us.  I'm going to have to have 
specific code to parse and build and register my devices.  If that could 
ends up registering a platform device or a newflatOF device I dont see any 
real difference.

> The alternative would be to represent all of the device tree
> in /sys/devices, but IMHO that should better be part of
> /sys/firmware with symlinks to the linux internal device tree
> representation.

Today I have:
  /sys/devices/platform/
			fsl-gianfar.1
			fsl-i2c.1
			fsl-i2c.2
			fsl-sec2.1
			fsl-usb2-dr.1
			fsl-usb2-mph.1
			serial8250
			serial8250.0

- kumar