Re: [PATCH] Open Firmware device tree virtual filesystem

From: David Miller
Date: Sun Dec 31 2006 - 00:20:01 EST

From: Mitch Bradley <wmb@xxxxxxxxxxxxx>
Date: Sat, 30 Dec 2006 15:38:46 -1000

> Request for comments.
> This patch creates a virtual filesystem that represents an Open Firmware
> device tree. It has been tested on an OLPC x86 system, but the code is
> not processor-specific (apart from its current location under arch/i386).
> It requires an Open Firmware implementation that can stay resident during
> Linux startup.
> It is similar in some respect to fs/proc/proc_devtree.c , but does not
> use procfs, nor does it require an intermediate layer of code to
> create a flattened representation of the device tree.
> The patch applies cleanly against the current version of
> git:// . (commit 5b9429be6056864b938ff6f39e5df3cecbbfcf4b).
> Please cc me (Mitch Bradley <wmb@xxxxxxxxxxxxx>) on comments.

Can we please not have N different interfaces to the open-firmware
calls so that perhaps powerpc and Sparc have a chance of using this
code too?

On sparc and powerpc, we even build an in-kernel data structure of the
entire open-firmware device tree that code like your's could use if
you make a simple setup layer for i386 as well. We have interfaces for
modifying property values at run time too.

I would strongly suggest looking at things like
arch/{sparc,sparc64,powerpc}/kernel/prom.c and
include/asm-{sparc,sparc64,powerpc}/prom.h and
arch/{sparc,sparc64,powerpc}/kernel/of_device.c and
since we've already invested a lot of thought and
infrastructure into providing interfaces to this information
on powerpc and the two sparc platforms.

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