[RFC] consolidated libdt proposal

Haren Myneni haren at us.ibm.com
Tue Aug 8 15:37:19 EST 2006

Hollis Blanchard wrote:

>On Sun, 2006-08-06 at 19:38 -0500, Hollis Blanchard wrote:
>>Hmm, so we'll have at least three copies of this code: uboot, kernel,
>>and Xen. Would it make sense to put this stuff into a libdt.a?
>>Technically, dtc has a "libdt" already, but it's absurdly incomplete
>>(I don't even know why it's there), so we could just replace it. 
>Mark, I had a look at the code Pantelis wrote for u-boot, and it was
>pretty easy to adapt to meet Xen's (userspace-based) needs. I've
>attached my version below (and see ft_setup() at the bottom of the
>file). Does it meet your requirements for the kernel bootwrapper?
>One limitation of the attached code is that it doesn't support changing
>the *size* of properties, though I don't think that would be too
>difficult to add if needed.
>Haren, what about using this in kexec-tools?

    Good idea to have this lib. Based on brief look, some of these funcs 
are also useful for kexec-tools. Yes, as you mentioned, changing the 
size of properties is important for kexec/kdump.

Present flattened device-tree process in kexec-tools:

- Kexec-tool reads the /proc/device-tree and sort these entries since we 
get the different order than the first kernel uses.
- creates linux,usable-memory property under /proc/device-tree/memory@* 
as appropriate.  (for kdump)
- Modify the reserve map for RTAS, initrd, TCE and (0- crashkernel-start)
- Create initrd properties if not exist in the first kernel as needed
- Modify bootargs property


>If everybody can use this (I expect small modifications would be
>needed), I think we should turn it into a library in the dtc source
>tree. The various projects using it could then include snapshots (to
>avoid dependencies). In general I'd like to avoid everybody writing and
>maintaining their own version of this stuff (myself included).

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