Messages in this thread | | | Subject | Re: Background to the argument about CML2 design philosophy | From | Jes Sorensen <> | Date | 21 May 2001 02:45:03 +0200 |
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>>>>> "Eric" == Eric S Raymond <esr@thyrsus.com> writes:
Eric> The first candidates I found were questions associated with Eric> built-in SCSI and Ethernet on Macintoshes, on the Sun 3 and Eric> Sun3x, and with built-in facilities on the MVME147 single-board Eric> computer. So I wrote derivations that looked like this:
[snip derive rules]
Eric> # These were separate questions in CML1 derive MAC_SCC from MAC Eric> & SERIAL derive MAC_SCSI from MAC & SCSI derive SUN3_SCSI from Eric> (SUN3 | SUN3X) & SCSI
Eric> By doing this I killed two birds with one stone -- got rid of Eric> some holes in Configure.help and (more importantly) moved the Eric> configuration experience away from low-level, hardware-oriented Eric> questions towards where I think it ought to be. That is, you Eric> specify a platform and the services you want and the ruleset Eric> computes the low-level facilities to be linked in.
And you suddenly imposed decisions on people.
Wether or not you are an expert it is reasonable to expect that you want to use modules just as it is just as reasonable to expect that you do not. In some cases you want your Ethernet as a module in some case you want the low level SCSI driver but not the SCSI mid layer.
Eric> After some back-and-forthing about the technical facts, several Eric> things emerged:
Eric> 1. The Mac derivations were half-right. The MAC_SCC one is good Eric> but Macs can have either of two different SCSI controllers. I Eric> fixed that with help from Ray Knight, who maintains the 68K Mac Eric> port.
Eric> 2. Nobody had a problem with the SUN3_SCSI derivation.
Did you ever get an ACK on it or no answer?
Eric> 3. The MVME derivations are correct *if* (and only if) you agree Eric> to ignore the possibility that somebody could want to ignore the Eric> onboard hardware, plug outboard disk or Ethernet cards into the Eric> VME-bus connector, and do something like running SCSI-over-ATAPI Eric> to the outboard device. (I missed these possibilities when I Eric> wrote the derivations.)
Or wants to use modules. And yes Aunt Tillie might want to do so, if the person who sold her her Linux CD provided a bunch of scripts for packing up things in a specific way.
Eric> The MVME situation is an almost perfect test case, because while Eric> breaking the assumption behind that derivation is physically Eric> possible it would be a rather perverse thing to do. The VME147 Eric> is an old design, dating from 1988; it's long since been Eric> superseded by MPCxxx SBCs based on the PowerPC that have a Eric> better processor, lower power consumption, and more on-board Eric> peripheral hardware. IDE/ATAPI didn't exist during most of its Eric> design lifetime, and the only way anyone is ever going to hook Eric> an outboard device to one of these puppies again is if some Eric> hacker pulls a dusty one off a shelf for some garage project.
Bzzzzt wrong. The MVME cards are still heavily used in control systems and similar places. It's the only place where m68k usage is not dying for real.
Eric> So far, I have to say I'm disappointed in the quality of the Eric> debate. Almoist nobody seems to want to think about this Eric> tradeoff globally, as a systems design issue. Instead, I'm Eric> hearing a lot of reflexive chuntering that we have to do things Eric> a certain way because we've always done them a certain way, and Eric> who am I to even dare *think* about raising different Eric> possibilities?
So far the introduction of CML2 has been overly disppointing, from day one it's been 'I have this great idea and since I think it's great, you obviously have to think so as well'.
Now I take it the derived rules are still only enforced under the 'novice' option, though you haven't exactly made that clear in the discussion (nor did you do so when you initially brought it up).
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