Re: [patch] linux 2.4.5: Export mips_machtype

On Thu, 23 Aug 2001, Gleb O. Raiko wrote:

In order to read a PCI ID, you need to know how to do it. In pc world,
you may rely on configuation access types, at least, ports are known. On
other arches, you need to know where such "ports" are. Even if hardware
supports, say, configuration type 1 accesses, developers are free to put
port addresses anywhere.

 Yep, I see.  MIPS is quite special here, because, unlike for Alphas,
PowerPCs, SPARCs, etc. there is a couple of independend vendors making
systems, so there is no single way of obtaining a system ID.  So you need
to know how to access chipset from elsewhere.

quoted

 How do you set up mips_machtype on your system in the first place?  At
kernel_entry the code does not know what machine it's running on anyway,
so it has to set mips_machtype based on a detection algorithm.

First, mips_machtype is accessed far later than kernel_entry is

 That's quite obvious -- nothing can be done in Linux earlier. ;-)  But
you need to initialize mips_machtype somehow.

executed. Personally, I am lucky :-), I may read firmware environment
variables.

 Well, other system might as well (e.g. DECstations can), but that doesn't
solve the problem -- to access firmware variables you need to know which
kind of firmware you are on. 

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +