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Re: [RFC] [IP22] parsing PROM variables at startup

To: Ralf Baechle <>
Subject: Re: [RFC] [IP22] parsing PROM variables at startup
From: Dmitri Vorobiev <>
Date: Tue, 13 Oct 2009 23:30:29 +0300
Cc: Linux-MIPS <>,
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On Tue, Oct 13, 2009 at 10:58 PM, Ralf Baechle <> wrote:
> On Tue, Oct 13, 2009 at 08:55:12PM +0300, Dmitri Vorobiev wrote:
>> I tried booting a few kernels, ranging from 2.2.1 to the current Linus
>> Git, on my IP22s using an ecoff image directly, without the help of
>> arcboot or tip22. It turns out that during many years (at least, since
>> the times of late 2.4 series) the sizes of ecoff images have been so
>> big that ARCS was not capable of reading the kernel images. Therefore,
>> I'd like to claim that it's safe to assume that at least from now on,
>> nobody is ever going to boot ecoffs on IP22 whatsoever, and arcboot
>> and tip22 remain the only way to load Linux on an IP22 machine.
> Only the very oldest IP22 firmware does not support ELF files.  In practice
> those seem to be very rare - I never encountered one - and Linux
> distributions are shipping a 2nd stage bootloader, so there never has
> been much of a need for booting ECOFF, at least not on Indy.

That is, it's safe to assume that it's either a 32-bit ELF or a 2nd
stage bootloader that gets loaded by the firmware.

>> I'm leading to the following thing. Currently we have the
>> arch/mips/fw/arc/cmdline.c, which assumes that the kernel could
>> receive command-line parameters directly from PROM, including such
>> variables as OSLoadPartition, OSLoadFilename, etc. Both arcboot and
>> tip22 handle those parameters by themselves, never exposing them to
>> the kernel. The latter fact is easy to see from the sources of the
>> arcboot and tip22 loaders. That said, I would like to simplify
>> arch/mips/fw/arc/cmdline.c::prom_init_cmdline() so that the PROM
>> variables do not get any special treatment.
> But keep kernels usable without a 2nd stage bootloader.  I for example
> have never ever used one on my SGI hardware.

OK, thanks for the notice. I'll see to it that the kernels are usable
if loaded directly by the firmware.


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