[U-Boot] [PATCH 0/2] Add support for the 32 bit boot protocol to the x86 zboot command.

[Gabe Black]

On Tue, Nov 29, 2011 at 7:48 PM, Graeme Russ <graeme.russ at gmail.com> wrote:

> Hi Gabe,
>
> On Wed, Nov 30, 2011 at 2:11 PM, Gabe Black <gabeblack at chromium.org>
> wrote:
> > These two patches add support for the 32 bit Linux boot protocol to the
> > zboot command.
>
> Going by our previous offline correspondence, I assume this approach still
> uses the bzImage's decompression stub?
>
> Also, as I discussion offline previously, I'm going through the boot_params
> with a fine-tooth comb to get a complete picture of what the Linux kernel
> actually requires to be filled out in the boot_params structure - I expect
> this will result in a 'built_boot_params()' function which is called by
> zboot and bootm - possibly with some weak stubs to helper functions
>
> Regards,
>
> Graeme
>

Yes, this supports the 32 bit protocol which includes the decompression
stub. I don't think a build_boot_params function which actually builds the
bootstub would work for a number of reasons. First, that's not how the boot
protocol works. The kernel provides information there that u-boot needs to
read, and u-boot shouldn't just make it up. An example of this is what boot
protocol is expected. Second, you might find all the things a particular
version of the kernel wants right now, but that could easy change at any
time and break booting. Third, the boot_params structure isn't compressed
(because otherwise the bootloader couldn't fill it out) and building our
own wouldn't serve any purpose.

If you mean consolidating the existing boot_params code so that both zboot
and bootm can use it, that seems reasonable. I'd point out, though, that
filling out the table takes a trivial amount of time, so trying to cut
corners and not fill it out completely would not only be dangerous, it
would very likely not be worth the effort.

Gabe