tech-net archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: no ndis* at cardbus?

On Jul 3,  4:09pm, Matthias Drochner wrote:
} said:
} > > For a minimal gain, it would make even more a mess of the
} > > PCI framework, and it would be in the way of proper
} > > PCIexpress/Expresscard support.
} > I think that you may have made some assumptions that you are not
} > telling us about. 
} It doesn't need assumptions, just facts.
} There are significant differences: autoconfiguration (no device
} addressing), interrupts and power management. The latter two
} are actually areas which are somehow delicate.
} Merging this into the PCI framework would require conditionals
} and hooks which noone would understand anymore after a while.
} (OK, that's an assumption, but a well based one.)
} In any case it is the opposite of modularity.
} Also, pci and cardbus are controlled by different standards
} bodies (PCISIG vs PICMG). This means that while it is already

     Um CardBus PC Card (the correct name for a "cardbus card") is
defined by PCMCIA.  PCMCIA also defines ExpressCard.

} The vendor/device IDs are kept coherent, but a chip designed
} for PCI will not work on cardbus unless specifically designed
} for this. So the cardbus namespace is much much smaller, and
} it will stay that way.
} A cardbus does only show up behind a "cbb", and we need a specific
} driver for cbbs anyway for power handling etc. This is quite
} different from the situation in PCI where we can handle unknown
} bridges because they are standardized.
} >From my perspective, deleting a zillion redundant device attachments
} There are nineteen atm, and while we might still grow some hardware
} support it will be a handful more if at all.
} Cardbus is dead, most new laptops don't have it.
} It's also not so rendundant because it contains the cardbus
} specific power handling. (I agree that some more code could
} be shared but I suspect that spec availability is a bit
} in the way here.)

     CardBus (note that the "B" is supposed to be capitalised) is
essentially hotswap PCI, so merging them would probably be a good
idea.  However, given the relatively small number of devices it may not
be worth it.  I don't know enough about PCIe / ExpressCard at this
point to form an opinion.

} And the cardbus code uses "rbus" which is somewhat fragile. Without
} a good reason I'd prefer to keep it away from the PCI code.

     It's on my project list to do something about this.  Right now,
16-bit PC Card (commonly known as "PCMCIA") is broken.  And, as you
note, CardBus is fragile.

}-- End of excerpt from Matthias Drochner

Home | Main Index | Thread Index | Old Index