Re: FW: HOT Plug and Expansion ROMs

["Monish Shah" <monish@hpfcmss.fc.hp.com>]

On Apr 4,  3:41pm, Tony Goodfellow wrote:
> Subject: FW: HOT Plug and Expansion ROMs
>
> The "HOT PLUG' proposal excludes the possibility of using Expansion ROMS
> for Adapter initialization.  This seems to be a retrograde step because:
>
> a) There are many cases where generations of an adapter might be register
> compatible to the HOST driver yet require different initialization
> procedures.  (Expansion ROM initialization is specific to the Hardware the
> ROM resides on.)

Counting on the expansion ROM to do your initialization has another
problem.  May be the expansion ROM won't be run at all.  In PC compatible
systems, this can happen if you run out of space for BIOS.  The BIOS code
must be copied to memory below 1M, so there is a limit to how many BIOSes
can be executed.

So, it is best to have your device driver do full initialization both
because of hot plug and because of BIOS space limitations.

I realize that Openboot firmware (which you described as F-code) is a
solution to both problems.  However, I suspect that having drivers do full
initialization is the path of least resistance for PC compatible systems.

> b) It does not seem to be in the spirit of "Hot Plugging" to require that a
> user replaces an "old" generation Adapter with the same "old" generation or
> figure out that some different driver has to be dynamically loaded.

It seems to me that replacing a "slightly" different device is the same as
replacing with a completely different device.  I.e., the old driver has to
be terminated and a new driver has to be started.  So, if the driver does
full initialization, as I suggest, then what you describe above is not a
problem.

Monish Shah
Hewlett Packard
t
c