Re: [Patch -v4 4/4] Make reboot_cpuid a kernel parameter. other cpus.

[Robin Holt <holt@sgi.com>]

On Tue, Apr 16, 2013 at 07:44:12AM -0500, Robin Holt wrote:
> On Tue, Apr 16, 2013 at 05:05:45AM -0700, H. Peter Anvin wrote:
> > Why not just support the existing syntax everywhere?
> 
> I have not given it much consideration, but IIRC, the other arches that
> were using reboot= were only looking for an 'h' or something like that.
> 
> I will consider making the syntax parse reboot=s#### when I get to
> the office.

Yesterday was rather disruptive and I did not get to this.  I have given
it some thought this morning.

Generally speaking, I don't like the feel of this for two reasons.  First,
having two different places that are parsing reboot=<reboot_mode> and
its related difficulty in documenting it.  Second, we lose the /sys/ file.

Some background.  First, arm.  It already has a reboot=<c>.  That <c>
gets passed to the reboot sub-arch function.  It looks like it is ignored,
but I am very uncertain of that as it is passed into an assembly routine.

Second unicore.  It parses as reboot=<c>.  That <c> gets ignored.

Now the meat of my question.  The Documentation/kernel-parameters.txt
file indicates reboot= is handled by the arch and are of the format
<reboot-mode>[,<reboot-mode>[,...]].

I suppose we could have both an arch and generic kernel handler for
__setup("reboot=",...)  where the generic kernel one just handles the
s###, but that seems really different from how everything else is done.
I could not find one instance where a both an arch and the kernel proper
both parsed the same command-line parameter.

I did not spend the time to see if having two __setup() declarations
would work.

Additionally, the __setup("... mechanism loses the nice feature the
core_param gives us in that there is a /sys/ file now available which
allows us to easily change that setting on the running system.

Are you really sure you want me to do more than I already have.  This
really feels _VERY_ wrong to me.  Maybe I misunderstood your direction.

Thanks,
Robin