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Date: Fri, 12 Oct 2001 10:44:08 -0700
From: Jun Sun <jsun@mvista.com>
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To: Geert Uytterhoeven <geert@linux-m68k.org>
CC: Ralf Baechle <ralf@oss.sgi.com>,
   Gerald Champagne <gerald.champagne@esstech.com>,
   "linux-mips@oss.sgi.com" <linux-mips@oss.sgi.com>
Subject: Re: Remove ifdefs from setup_arch()
References: <Pine.GSO.4.21.0110121350300.20566-100000@mullein.sonytel.be>
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Geert Uytterhoeven wrote:
> 
> On Wed, 3 Oct 2001, Jun Sun wrote:
> > I talked about machine detection a while back.  My idea is following:
> >
> > 0. all machines that are *configured* into the image will supply <my>_detect()
> > and <my>_setup() functions.
> >
> > 1. at MIPS start up, we loop through all <my>_detect(), which returns three
> > values, a) run-time detection negative, b) run-time detection positive, and c)
> > no run-time detection code, but I return positive because I am configured in.
> >
> > 2. the startup code resolves conflicts (which sometimes may panic); and decide
> > on one machine.
> >
> > 3. then the startup code calls the right <my>_setup() code which will set up
> > the mach_type and other stuff.
> 
> Nice!
> 
> I suppose you want to have struct containing pointers to both the detect() and
> setup() functions, so you know which setup() function you have to call?
> 

The actual mechanism can vary and be flexible, but here is more detail what I
had in mind:

1. <my>_detect is placed in a special ELF section (mips_mach_detect), using
similar mechanism as .initcall.init section and __setup() macro.

2. in addition to the 3 possible return value, <my>_detect also returns a
function pointer to <my>_setup.  Once a final candidate is chosen, the machine
detection code will issue the right <my>_setup call.

There are probably some other related changes which need to be made, (e.g.,
prom_init() may be eliminated, etc).

It seems like I get more and more positive feedbacks on this idea.  We should
try to implement this in 2.5.

Jun