Subject: Re: A TODO list for cardbus/ PCMCIA support.
To: Jonathan Stone <jonathan@DSG.Stanford.EDU>
From: Chris G. Demetriou <>
List: tech-kern
Date: 06/16/1999 19:10:54
Jonathan Stone <jonathan@DSG.Stanford.EDU> writes:
> But I'm not sure we're talking about the same problem. As best I
> understand Hayakawa-san, the problem whichthe current CardBus patches
> address is that bridges only support a subset (window) of the
> parent-bus (e.g., PCI) on their child-bus side (e.g., CardBus); and
> the devices on the child-bus have to be bin-packed into that window.
> Thats different from itrying to pack all the child-devices'
> requirements togehter and then allocating the bridge enough space to
> hold the total requirements -- which is how I read your message.

They're all facets of the same parent.

* what if the CBB doesn't have an address assigned to begin with,
e.g. because the BIOS doesn't understand header-type-2 devices?  (you
need to pack it in its parent.)

* what if a hba's or PPB's subdevices aren't (all) configured?

They're all different facets of the same problem, and should be
addressed with a single mechanism.

> Perhaps best is to figure out what the base is going to be, given info
> on the bridge; pack the children of the far-side of the bridge at
> addresses commensurate with what the bridge can handle (e.g., due to
> the bridge ignoring some address bits), and finally relax the size
> of all the childre to get the final size allocated for the brige.
> (is that comprehensible?)

I understand how it's supposed to be done, so i understand what you're
trying to say.

In fact, i'd venture that for things like card bus bridges instead of
allocating the amount of space used for actual devices behind the
bridge, you want to say "(if not already configured) reserve this much
of these types of spaces for devices behind the bridge."  So, you
still have to pack the children beneath the CBB, and still have to
pack the CBB into its parent, but don't have to worry about using the
result of the former for the latter, as you need to for PPBs.

> OK. Chris, can you get in touch with Hayakawa-san?

Actually, it seems like this is the right place to discuss it.

Time to go back upstairs...  my PCI docs are currently on my coffee
table...  8-)

Chris Demetriou - -
Disclaimer: Not speaking for NetBSD, just expressing my own opinion.