cvs commit: src/sys/dev/pci pci.c

[Gavin Atkinson]

On Mon, 2004-05-24 at 04:57, M. Warner Losh wrote:
> In message: <20040523204728.U66525 at root.org>
>             Nate Lawson <nate at root.org> writes:
> : On Sat, 22 May 2004, M. Warner Losh wrote:
> : > Well, we're talking exclusively about the vendor, device, subvendor,
> : > subdevice, class, subclass and progif fields, which are obstensively
> : > read-only.  However, the pci standards are self-contradictory.  The
> : > main 2.2 one says they are read-only (without defining what that means
> : > that I could find), yet the pciide spec says that progif had writable
> : > bits...
> : 
> : I think the progif is the only one of that list that you need to restore,
> : as per your reading of the specs.  Since the others are identifiers, they
> : probably don't need to be restored.
> 
> Things are vague enough in the spec that this is totally
> unsatisfying.  We're just guessing based on hunches, which I really
> don't like, which is why I saved/restored everything.

Could we perhaps read them on restore and only write to them if
necessary? That way we reduce the possibility of tickling bugs in the
silicon by writing to read-only registers for chips that don't actually
need it?

Gavin