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SubjectRe: USB device allocation
[Johannes Erdfelt <jerdfelt@sventech.com>]
> On Tue, Oct 05, 1999, Brian Swetland <swetland@be.com> wrote:
> >
> > Wait! Why couldn't all devices just show up dynamically? You'd only
> > see the devices that were actually on the system (at that moment). Wait,
> > somebody already made this work! Ye gods, the anarchy.
> >
> > Why should a usb zip drive, parallel zip drive, or scsi zip drive be
> > different to access? They all speak the same protocol. You don't have
> > a different driver for a scsi disk on a buslogic controller and a scsi
> > disk on an adaptec controller, do you?
>
> Neither do you with USB. It uses the same SCSI disk driver. Perhaps I'm
> missing your reference?
>
> For all of the "standard devices" (this is vaguley defined) it uses one
> of the standard device nodes. In the case of USB zip drives, etc it
> shows up as the next sd* device.

Ah, you're totally right. The casual dismissal of devfs (something I
really think is a great idea especially after seeing how nicely it works
in BeOS) got my ranting more than thinking. My bad.

To use the BeOS model for such things (I know what the names are like
better there):

scsi_disk -> scsi_bus_manager -> usb_sim -> usb_bus_manager -> uhci_hcd

Where scsi_disk is a device driver and everything below is a module.

I'll still maintain that dynamic publishing of devices is a huge win,
though in this case it's not (directly) applicable.

Brian

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