Messages in this thread | | | From | Segher Boessenkool <> | Subject | Re: [PATCH] Open Firmware device tree virtual filesystem | Date | Thu, 11 Jan 2007 19:47:10 +0100 |
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>> I'd like to put in my $.02 in favor of having a way to pass the OF >> device tree to the kernel, in much the same way we pass stuff like >> ACPI and PIRQ and MP tables now. > > This works fine for just passing the device tree, but it will fail for > the next step of being able to use the firmware in the OS, and > returning > sanely to the firmware.
Not everyone wants/needs that. Flexibility is key.
>> - any path that uses kexec (since the first kernel probably shut down >> OF) > > No, that path works fine. The first kernel uses OFW, so it wont shut it > down. Only thing is you need to pass the callback to the loaded kernel.
Depends. The kernel _can_ shut down OF; in that case, it becomes responsible for passing the device tree along to the kexec'd kernel.
>> - etherboot > > ok, well.
Heh :-)
>> OFW is open source now. I think it's time to reexamine the basic >> assumptions about the need for a callback, and see if something better >> can't be done. > > I fully agree. And I believe there are very good things that can be > done > with callbacks. The reasons callbacks are evil is that you dont know > what you call into. This is not at all the case here. It's a mere > function call that calls some highly board specific code, not unlike > all > the calls we do in LinuxBIOS already today. Since we're 100% open > source, we don't "cross a border" anymore.
Oh you *do* cross a border, and that is a good thing here; it is a stable API, and that makes a lot of sense here.
> - 16bit legacy callbacks > - (u)efi legacy callbacks > - existing openfirmware support code for non-x86 platforms. > > But: It is a first step that, as a mid-term goal, allows us to unify > OFW > support on all platforms to some extent.
Yes.
>> Mitch, is there some way to get OF device tree to the kernel without >> involving a callback? That would be quite nice. > > That is a nice idea, but unless there is any LinuxBIOS version that > creates such a device tree and exports it as a data structure to the > OS, > why would we want to add such support to the Linux kernel?
The PowerPC arch code already handles this.
Segher
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