[PATCH 0/3] patches to allow DTB to be appended to the ARM zImage
grant.likely at secretlab.ca
Mon Jun 13 19:33:53 EDT 2011
On Mon, Jun 13, 2011 at 4:05 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Mon, Jun 13, 2011 at 08:24:27PM +0000, Dmitry Eremin-Solenikov wrote:
>> Russell King - ARM Linux wrote:
>> > On Sun, Jun 12, 2011 at 05:01:22PM +0200, Arnd Bergmann wrote:
>> >> Of course it should override the device tree, I'm not arguing that.
>> >> All I'm saying is that we don't need to special-case this or support
>> >> both formats once the kernel is there as long as we move the information
>> >> into appropriate DT-representation of the same data.
>> > You're arguing for it to be parsed by whatever fragment of assembly code
>> > we have to place around the zImage to merge it into DT.
>> > And yes, it's going to have to be assembly code because we don't have a
>> > C environment at that point which can run in a relocatable way.
>> Please, again look at the cuboot stuff which is used on powerpc. It uses
>> limited C environment: it's executed before kernel entry, so it can use
>> stack, etc. as setup by the bootloader.
> Boot loaders don't pass a stack to the kernel - what may be in the
> stack pointer may not be valid at the point when the kernel is called -
> it may be that it can only be used while the MMU is on, and at this
> point the MMU will be off. So you can't rely on anything from the
> boot loader which I haven't documented as being part of the ARM kernel
> boot protocol.
> Please understand that we absolutely must get this issue resolved before
> the next merge window, and have a solution ready to be merged at that
> point. As I see it, this is one of the major issues that requires
> addressing. Why?
John Bonesio is working on it this week (starting tomorrow), and will
get an updated patch out ASAP.
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