Re: [RFC] [PATCH] Device Tree on ARM platform

From: Sergei Shtylyov
Date: Wed May 27 2009 - 15:46:31 EST


Russell King wrote:

smc91x is a prime example of the kind of information drivers need - base
address and irq are very much insufficient to describe how this device is
connected. There's much more information required to specify this device
fully, and throwing it into the driver doesn't work. We've been there
and proven that point.

The device tree is quite capable of expressing information beyond addresses and interrupts.

Bus width? Register offset spacing? SMC LED configuration? Whether
to use the hardware wait signal from the SMC?

Yes, it's perefectly capable of all that. In fact, the first two items have already been defined for MTD and serial devices (though I wasn't happy about how the 2nd item was done IIRC).

If you're going to say yes to all that, I'm going to start asking how
you cope with verifying that the data for ethernet driver A doesn't
get accidentally used for ethernet driver B.

It's incorporated into the device node corresponding to Ethernet device A, which driver B doesn't drive.

I assume you have some kind of compiler, which needs a set of specification
files to tell it what's required for each driver which is OF compatible.

The compiler is called (surprise :-) 'dtc'.

If not, I can see no way for OF trees to ever be safe and correct.

WBR, Sergei
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