Re: [PATCH] Open Firmware device tree virtual filesystem

From: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx>
Date: Mon, 1 Jan 2007 04:33:13 +0100

All we've done is created a trivial implementation for exporting
the device tree to userland that isn't burdened by the powerpc
and sparc legacy code that's in there now.

So now we'll have _3_ different implementations of exporting
the OFW device tree via procfs. Your's, the proc_devtree
of powerpc, and sparc's /proc/openprom

That doesn't make any sense to me, having 3 ways of doing the same
exact thing and making no attempt to share code at all.

Not the same exact thing -- using a text representation for
the property contents is a very different thing (and completely
braindead).

The filesystem bit is for groveling around and getting information
from the shell prompt, or shell scripts. Text processing.

If you want the binary bits, export it with something like
/dev/openprom. We don't generally export binary representation
files out of /proc or /sys, in fact this rule I believe is layed
our precisely somewhere at least in the sysfs case.

Every architecture that supports the device tree filesystem,
initialises a "struct device_tree_ops" with a bunch of
pointers to functions that allow you to traverse the device
tree and read its properties (and maybe write properties, or
even delete and create new nodes. The devtree filesystem code
simply calls into these functions to do the actual operations
on the device tree (access an in-kernel data structure, call
the OF, or both -- or something entirely different, who knows).

That's the only key point in my opinion, any clean interface that
sits in front of this stuff is fine as long as it encompasses
all of the necessary operations and allows just about any
implementation underneath.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages