Date: Mon, 23 Dec 2002 13:17:36 -0800 From: Marcel Moolenaar <marcel@xcllnt.net> To: "M. Warner Losh" <imp@bsdimp.com> Cc: perforce@freebsd.org Subject: Re: PERFORCE change 22623 for review Message-ID: <20021223211736.GB660@dhcp01.pn.xcllnt.net> In-Reply-To: <20021222.233348.122304694.imp@bsdimp.com> References: <20021222231958.GA1414@athlon.pn.xcllnt.net> <20021222.200921.66023382.imp@bsdimp.com> <20021223033542.GA2039@athlon.pn.xcllnt.net> <20021222.233348.122304694.imp@bsdimp.com>
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On Sun, Dec 22, 2002 at 11:33:48PM -0700, M. Warner Losh wrote:
> In message: <20021223033542.GA2039@athlon.pn.xcllnt.net>
> Marcel Moolenaar <marcel@xcllnt.net> writes:
> : > I just remeber when I did it that it was a big deal to me and to the
> : > folks that hired me to create a pci driver for the controller based
> : > modems. Maybe things have changed, and if so I'm cool with things
> : > going away. But if they haven't changed, this needs to stay around
> : > until the underlying problems are fixed.
> :
> : The console problem has gone now that we only care about the tag
> : and handle. The disconnect can still be confusing to people, but
> : as I said above, this applies to any device that uses/needs hints.
>
> OK. As long as the console problem is gone, I'm happy. The hint/unit
> disconnect is something that needs to be addressed, but that's a much
> uglier issue.
This is what I figure: We need to change the semantics of the hints
if we want to have consistency. Hints can be given gratuitously now,
which decreases their value to the point that they are referenced
as a last resort. This includes the PnP case where there are multiple
possible settings and as long as there's no conflict either of those
settings is equally valid. Hints will help us decide only. Thus, hints
are lacking the "authority" to force or dictate behaviour.
If we remove the need for hints in cases it isn't required and we
stop the gratuity of them being given, we can turn them into
reservations. Let's explain with an example:
In a machine M are two identical ethernet interfaces, one at address
A0 and one at address A1. Bus enumeration has caused the assignment:
foo0: <ACME ether products> at address A1, and
foo1: <ACME ether products> at address A0
Also present in machine M are two serial interfaces of which one is
auto-detected (PnP) and placed at address A2. The placement is from
the set S={A2,A3,A4} of possible settings. The assignment yields:
ser0: <ACME serial products> at address A2
The second serial interface cannot be found by bus-enumeration and
also happens to be hardwired (jumpered) at address A2. The user likes
to use that one as the console and wants it given unit 1.
Picky as the user is, he also likes foo0 at address A0 and foo1 at
address A1.
If hints are reservations, the following may possibly achieve what
the user wants:
foo.0.address=A0
ser.1.address=A2
serial_console=A2
The logic (in chronological order) would be something like:
/* {t1,t2}: Make reservations */
t1 Reserve unit 0 of devclass foo for address A0
t2 Reserve unit 1 of devclass ser for address A2
/* {t3}: Console probing */
t3 Probe serial console at address A2; unit unknown
/* {t4,t6}: Bus enumeration */
t4 found unreserved foo at address A1; first free unit 1
t5 found reserved foo at address A0; unit 0
t6 found unreserved ser at {A2,A3,A4}; first free unit 0;
first free resource A3
/* {t7}: Probe reserved undetected devices */
t7 Undetected reserved ser at address A2; unit 1, console
Note that if hints are reservations, the use of unit numbers for
console devices is possible, provided a reservation exists that
ties it to an address. Thus:
serial_console=unit:1
ser.1.address=mem:0x1234
If there's no reservation, serial consoles have to be defined in
terms of addresses:
serial_console=port:0x3f8
(the prefix "unit", "mem" or "port" is for illustrative purposes)
Anyway: just some thoughts...
--
Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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