On Sun, Jun 13, 2010 at 11:02:15PM -0600, Grant Likely wrote:
[sni]

quoted

That's sort of a self-fulfilling prophecy.  If the OS doesn't trust the
firmware, there is no pressure for the firmware to "get it right".

Firmware will not get it right.  Period.  There will always be
something wrong.  It is never right on PCs.  It will never be right on
the other architectures.

Yes, yes, yes.  And there is a great deal of empirical evidence to
back that assertion.

 That goes for OSes too, but upgrading an OS
isn't as risky as upgrading firmware.  That isn't to say that it can't
be close, but every firmware feature that the OS depends on is a
feature that could force a risky firmware upgrade when the bug in it
is discovered.

Indeed.  In fact, the general rule of thumb is really "put as much as
possible into the most easily replaced layer of the stack".  This is,
incidentally, why I've always been dubious about simple firmwares
supplying a flattened device tree rather than including the device
tree template in the kernel, cuboot style.

I'm also convinced that the economics are all wrong for "getting it
right" when talking about firmware.  Manufactures don't care about
firmware; they care about selling boxes.  Customers don't care about
firmware, they care about the operating system (well, that's not true
either, they care about applications).  For manufactures, once it can
boot the real operating system, there is little to no incentive to
spend any more money on firmware when the money can be better spent on
either the next product or the adding features to the operating system
of the existing product.  In fact, spending money on firmware is
actually *more risky* one a product ships, because if a firmware
upgrade goes bad, then that means product returned for repair at the
factory.

A good analysis.  The other side of this, is that for an OS, if you
rely on the firmware to do X, it will work when the firmware gets it
right.  If you do X yourself, it will work whether or not the firmware
gets it right.  This means that if there's even one firmware you have
to deal with out there that gets X wrong, you have to do it yourself
and then there is little to no incentive to rely on firmware even in
the cases where it does get it right.  In fact there's a disincentive,
because then you have two different code paths to test and maintain.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson