From: David Laight <David.Laight@ACULAB.COM>
To: "'Maciej W. Rozycki'" <macro@orcam.me.uk>
Cc: Rich Felker <dalias@libc.org>,
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"David S. Miller" <davem@davemloft.net>
Subject: RE: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary
Date: Fri, 6 May 2022 13:28:42 +0000 [thread overview]
Message-ID: <3669a28a055344a792b51439c953fd30@AcuMS.aculab.com> (raw)
In-Reply-To: <alpine.DEB.2.21.2205061412080.52331@angie.orcam.me.uk>
From: Maciej W. Rozycki
> Sent: 06 May 2022 14:15
> On Fri, 6 May 2022, David Laight wrote:
>
> > > The PCI configuration space was retrofitted into x86 systems (and is
> > > accessed in an awkward manner with them), but with a new design such a
> > > clean approach is most welcome IMHO. Thank you for your explanation.
> >
> > Actually I think x86 was the initial system for PCI.
> > The PCI config space 'mess' is all about trying to make
> > something that wouldn't break existing memory maps.
>
> It was retrofitted in that x86 systems already existed for ~15 years when
> PCI came into picture. Therefore the makers of the CPU ISA couldn't have
> envisaged the need for config access instructions like they did for memory
> and port access.
Rev 2.0 of the PCI spec (1993) defines two mechanisms for config cycles.
#2 is probably the first one and maps all of PCI config space into
4k of IO space (PCI bridges aren't supported).
#1 requires a pair of accesses (and SMP locking).
Neither is really horrid.
For horrid try the ISApnp interface.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
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next prev parent reply other threads:[~2022-05-06 13:29 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220429135108.2781579-1-schnelle@linux.ibm.com>
2022-04-29 13:49 ` [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary Niklas Schnelle
2022-05-01 22:40 ` Maciej W. Rozycki
2022-05-04 21:08 ` Bjorn Helgaas
2022-05-04 21:31 ` Arnd Bergmann
2022-05-05 8:10 ` Niklas Schnelle
2022-05-05 16:10 ` Bjorn Helgaas
2022-05-05 17:39 ` Arnd Bergmann
2022-05-05 19:53 ` Bjorn Helgaas
2022-05-06 9:12 ` Finn Thain
2022-05-06 11:18 ` Niklas Schnelle
2022-05-07 0:01 ` Finn Thain
2022-05-07 13:14 ` Arnd Bergmann
2022-05-07 23:59 ` Finn Thain
2022-05-08 0:15 ` Finn Thain
2022-05-06 9:38 ` Niklas Schnelle
2022-05-06 11:07 ` John Garry
2022-05-06 10:20 ` Maciej W. Rozycki
2022-05-06 11:33 ` Arnd Bergmann
2022-05-06 12:27 ` Maciej W. Rozycki
2022-05-06 12:53 ` David Laight
2022-05-06 13:08 ` Geert Uytterhoeven
2022-05-06 13:40 ` Maciej W. Rozycki
2022-05-06 14:03 ` David Laight
2022-05-06 15:02 ` Geert Uytterhoeven
2022-05-06 13:15 ` Maciej W. Rozycki
2022-05-06 13:28 ` David Laight [this message]
2022-05-06 14:44 ` Maciej W. Rozycki
2022-05-06 14:56 ` Geert Uytterhoeven
2022-05-06 15:03 ` Maciej W. Rozycki
2022-05-06 12:53 ` Arnd Bergmann
2022-05-06 13:15 ` Niklas Schnelle
2022-05-06 13:16 ` Maciej W. Rozycki
2022-05-06 12:55 ` Niklas Schnelle
2022-05-06 12:42 ` Niklas Schnelle
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