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SubjectRe: POSTing of video cards (WAS: Solo Xgl..)


On Mon, 21 Feb 2005, Jon Smirl wrote:
>
> I was working on the assumption that all PCI based, VGA class hardware
> that is not the boot device needs to be posted.

I don't think that's true. We certainly don't _want_ it to be true in the
long run - and even now there are cards that we can initialize fully
without using the BIOS at all.

> And that the posting should occur before the drivers are
> loaded.

Personally, I'd much rather let the driver be involved in the decision.

That may mean that the probe routine knows how to initialize the card, but
it may mean that it does an "exec_usermodehelper()" kind of thing.
Actually, I'd prefer it if this was largely up to "udev": if the driver
notices that it can't initialize the card, why not just enumerate it
enough that "udev" knows about it (that's pretty much automatic), and let
the driver just ignore the card until some (possibly much later) date when
the user level scripts have found it and initialized it.

That would imply that the driver have some "re-attach" entrypoint (which
migth be a ioctl, but might also be just a /sysfs file access), which is
the user-lands way of saying "try again - I've now initialized the
hardware".

The advantage of that kind of "disconnected" initialization is that you
don't _need_ to have the card initialization in initramfs or other "very
early boot" sequence. It gets _detected_ early on, but you can then delay
initializing it arbitrarily long, and it obviously won't be usable until
that point (but who cares? The ones that do care can put the things in
their initramfs, others may decide to do it only once the system is
up-and-running and /usr has been NFS-mounted).

Linus
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