Messages in this thread | | | Date | Sun, 31 Dec 2006 01:52:10 -0800 (PST) | Subject | Re: [PATCH] Open Firmware device tree virtual filesystem | From | David Miller <> |
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From: Mitch Bradley <wmb@firmworks.com> Date: Sat, 30 Dec 2006 23:36:45 -1000
> The base interface function is callofw(), which is effectively identical > to call_prom_ret() in arch/powerpc/kernel/prom_init.c . So it seems > that PowerPC could use it. I suppose I could change the name of > callofw() to call_prom_ret(), thus making the base interface identical > to PowerPC's. All it does is argument marshalling, translating between > C varargs argument lists and the OFW argarray format.
Please create explicit function calls for each operation, this way the caller is immune to open-firmware implementation details.
> SPARC should be able to use that same base interface function directly. > It is written to the standard OFW client interface.
Sparc 32-bit predates the OFW specification and does things differently.
Please use a functional interface using a C function for each device tree operation, then the implementation behind it doesn't matter.
> It wouldn't work on ancient Sun machines with the sunmon romvec > interface, but Sun stopped making such machines something like 16 years ago.
Yet we still support them in the 32-bit sparc port. And it's so easy to support this properly, please use the clean stuff we've created for this.
> I did consider first creating a memory data structure identical to the > powerpc/sparc one, but that looked like it was going to be essentially > twice as much code for no extra capability. The code to traverse the > device tree and create the memory data structure is roughly the same as > the code to create the filesystem structure. I just didn't see the > value of an intermediate representation for systems that don't otherwise > need it.
Since we put it in memory, we have zero reason to call into the firmware for device tree access and this simplifies things a lot.
But all of that really doesn't matter, if you use a functional C interface for each device tree access operation, it doesn't matter what's behind it right? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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