Re: [Linux-fbdev-devel] Re: Who is stomping PCI config space?

Benjamin Herrenschmidt writes:
 > > 
 > > If we leave the whole card turned off I can't access the interrupt
 > > status registers to acknowledge the interrupt and shut it off.
 > 
 > Also, some cards won't let you switch VGA access decoding off.

This is what I suspect. I had some success with the generic VGA disable
code but our mileage may vary.

 > 
 > > Does this approach work for X? Where is the code that does this at VT
 > > switch time?
 > > 
 > > On VT enter X would need to:
 > > 1) shut off interrupts
 > 
 > Not possible (system interrupts). Unless it does it on the card itself,
 > which is a per-driver thing.

How do we deal with interrupts from VGA cards that we don't have a 
driver for? We don't service interrupts in this case either.
Can't we unregister the interrupt handler until everything
is set up right? Maybe a dump idea...
Also there is a generic VGA register to control interrupts.


Egbert.

How do we deal with interrupts from VGA cards that we don't have a 
driver for? 

We don't get any, do we ? If we get an interrupt we don't have a driver
for, the system dies usually ;) Well, unless it's an edge interrupt, in
which case we can just drop it on the floor, but PCI interrupts are
level.

We don't service interrupts in this case either.
Can't we unregister the interrupt handler until everything
is set up right? Maybe a dump idea...
Also there is a generic VGA register to control interrupts.

We have reached the end of my VGA knowledge, but I seriously doubt a VGA
card will issue interrupts if not previously programmed to do so... So
we probably don't have to bother. We only care about interrupts that we
have a use for, that is interrupts triggered by cards upon request of
their driver, for things like DMA/AGP command buffer operations, vblank,
monitor detection, ...

Ben.