[LinuxBIOS] Specifications

[Peter Stuge]

On Thu, Jun 14, 2007 at 05:28:26PM -0600, Jordan Crouse wrote:
> We don't configure sound cards, or initialize NICs, or any of those
> things.

Well, we sort-of do.


> The point is, that LinuxBIOS shouldn't really be required to leave
> individual devices in any sort of sane state.

It should leave devices in a "reachable" state. Depending on the bus
they are connected to this may or may not imply some level of sanity.


> > Why would LinuxBIOS not initialize serial console, but a payload
> > would? If LinuxBIOS does not initialize it, it's not there.
> 
> Again, words get in the way.  LinuxBIOS does initalize and
> enumerate it, but I don't really think that the intent is to
> require LinuxBIOS to tromp out and touch the 16550 and set baud
> rates, and other such configuration settings so that the payload
> doesn't have to.  Am I wrong?

I think so, for the specific case of the console serial port (or a
replacement).

The serial port (or replacement) is crucial for developers and
initially it was also crucial for users. Those users are still
around but now we also want to help users that consider other
devices to be crucial.


> I think LinuxBIOS is there to initalize and enumerate the hardware
> at a very low level.  I don't think it is there to be a surrogate
> serial / smbus / IDE / VGA / whatever driver for payloads that
> don't wish to implement those things on their own.

This is a very important point and I agree completely.

LinuxBIOS is not a set of drivers and does not provide services.


> Of course, I say that because I'm pretty much only interested in
> loading payloads that do support those services on their own

Software needs system buses to be in a "working" state where devices
are "reachable" and some of us considers this to imply that devices
are "initialized" and set to some state because they have in fact
been touched while others consider only the bus itself to be
initialized.

Both are completely accurate, they actually mean the same thing.

Devices are never _driven_ by LinuxBIOS after the payload has been
started however, and most devices aren't driven before the payload
starts either.

However - LinuxBIOS will need to "hand over" the system to the
payload and I guess that the formalization of this handover is what
this thread is all about. It should include providing the payload
with information about how the system is set up as of now so that
good payloads can be written which will work on any setup.


//Peter