Date: Tue, 24 Aug 2010 10:09:46 -0400 From: John Baldwin <jhb@freebsd.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: yanegomi@gmail.com, freebsd-hackers@freebsd.org Subject: Re: Why doesn't ppc(4) check non-ENXIO failures during probe? Message-ID: <201008241009.46624.jhb@freebsd.org> In-Reply-To: <20100823.220945.232861953240012158.imp@bsdimp.com> References: <201008170907.20593.jhb@freebsd.org> <201008171615.21103.jhb@freebsd.org> <20100823.220945.232861953240012158.imp@bsdimp.com>
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On Tuesday, August 24, 2010 12:09:45 am M. Warner Losh wrote: > In message: <201008171615.21103.jhb@freebsd.org> > John Baldwin <jhb@FreeBSD.org> writes: > : > So more or less it's for BIOSes with ISA that doesn't feature plug > : > and play (286s, 386s, some 486s?)? Just trying to fill in the gap :). > : > : Yes, it may perhaps still be useful for some x86 embedded systems, though > : it is doubtful that those would use a ppc(4) device perhaps. > > Many embedded x86 systems use ppc(4) as a DIO port. ppi attaches to > it and can be used to frob bits. > > These days, of course, almost all boards have ACPI, so that means they > get enumerated that way. Only boards that don't run windows might not > have ACPI, in which case the devices are usually enumerated via > PNPBIOS. But not always, since those boards tend to have the buggiest > BIOSes on the planet in this area. Hints are needed on a few of these > boards since nothing else will work. And they have Atom processors on > them... The specific code I am referring to is the code in ppc_isa_probe() that tries to auto-identify a ppc port by poking at various I/O ports directly. It is not enabled by default. You'd have to have a ppc hint that did not include an I/O port for this code to be triggered I think as it only gets executed if a ppc(4) device does not have an I/O port resource from ACPI/PnPBIOS/hints. I was mostly thinking of this in terms of ISA cards, and I doubt that even modern embedded systems have ISA slots. :) -- John Baldwin
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