Re: DeviceID in a multi-function device.

[Udi Finkelstein <udif@bigfoot.com>]

On Mon, 27 Nov 2000 12:06:03 -0800, Richard Walter <rwalter@Brocade.COM>
wrote:

>Folks,
>

>However, from the logical standpoint of functionality, the fact that two functions are sharing the same silicon doesn't mean that they are related at all.  Therefore,  the answer could be "no", that the DeviceID doesn't need to be the same for all functions in a multi-function device.

PCI multi-function devices are a way to combine multiple, totally distinct PCI
devices on the same silicon/board.

Think about PCI adapter #1, which is a SCSI controller with VID/DID pair #1.
Think about PCI adapter #2, which is a Network controller with VID/DID pair
#2.

Both cards have widespread, multiple O/S device driver support.

Now think 1-2 years down the road. The manufacturer wants to combine both
cards into a new "combo" card containing both SCSI and Network functions (or
maybe a multi-channel SCSI device), yet keeping the same device drivers:

Think about PCI adapter #3, with function #0 which is a SCSI controller with
VID/DID pair #1, and function 1 which is a Network controller with VID/DID
pair #2.

Now, PCI adapter #3 should work using the old device drivers, if these drivers
were written correctly to scan all the PCI slots and all the PCI functions in
search of the correct VID/DID.

This was always what I thought was the main reason for multi-function devices
(supporting legacy device drivers in the field).
You could also use multi-function devices to gain more BARs.

>-Richard Walter
>Hardware Engineer
>Brocade Communications Systems
>rwalter@brocade.com
>Note: I speak for myself, not for Brocade.

Udi