Re: [parisc-linux] Untested port of parisc_device to generic device interface

From: Greg KH (
Date: Sat Nov 09 2002 - 01:03:42 EST

On Sat, Nov 09, 2002 at 05:21:50AM +0000, Matthew Wilcox wrote:
> Everyone's saying "ra! ra! generic device model!" without asking
> what the cost is. Don't you think it's reasonable that _as the most
> common device type_, struct device should be able to support PCI in a
> clean manner?

No I do not.

> Don't you think that the fact that it fails to do so is a problem?

Yes I do.

> Don't you look at the locks sprinkled all over the struct device
> system and wonder what they're all _for_?

Nope :)
(yes, I do wonder, and yes, they will be cleaned up...)

> Don't get me wrong. I want a generic device model. But I think it's
> clear the current one has failed to show anything more than eye candy.
> Perhaps it's time to start over, with something small and sane -- maybe
> kobject (it's not quite what we need, but it's close). Put one of those
> in struct pci_dev. Remove duplicate fields. Now maybe grow kobject a
> little, or perhaps start a new struct with a kobject as its first member.

No, lets start pulling stuff out of pci_dev and relying on struct
device. The reason this hasn't happened yet is no one has been willing
to break all of the PCI drivers, yet.

I know Pat is going to be doing this soon, and if he doesn't get to it,
I will. But as Adam said, don't throw away the idea because it looks
crufty now. This has been a _constantly_ evolving model as we work to
get it right. It will take time, and we are still getting there.

> And, for gods sake, don't fuck it up by integrating it with USB too early
> in the game.

In my defense, USB was the _only_ bus willing to step up and try to do
the integration to work the initial kinks out. The SCSI people are
being drug kicking and screaming into it, _finally_ now (hell, SCSI is
still not using the updated PCI interface, those people _never_ update
their drivers if they can avoid it.)

> Let's get it right for PCI, maybe some other internal busses
> (i'm gagging to write an EISA subsystem ;-). SCSI is more interesting
> than USB. Above all, don't fall into the trap of "It's a bus and it
> has devices on it, therefore it must be a part of devicefs".

Sure SCSI's more interesting, to you :)

By having USB be one of the first adopters (after PCI), we have found a
_lot_ of issues and bugs that happened due to devices showing up and
disappearing at odd times. Which was _much_ easier to debug than PCI
would have been. SCSI can't even do hotplug devices _yet_. How would
we have debugged this stuff then?

And yes, USB belongs in the model, if for no other reason, that "it's a
bus and it has devices on it" :)

> *sigh*. halloween was a week ago.

Patches for this stuff are going to be happening for quite some time
now, don't despair.

And they are greatly appreciated, and welcomed from everyone :)


greg k-h
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