[Open-graphics] VGA BIOS

[Timothy Normand Miller]

On 9/8/07, Paul Brook <paul at codesourcery.com> wrote:
>
> PIO regs are nice for debugging and poking at the card state from within a
> running machine. However I'm not so sure about actually using them in anything
> approaching a real driver. I guess with appropriate abstraction the driver
> may be able to use either.

I meant only a prototype driver.  Also, the framebuffer driver for the
linux kernel might use PIO.

> In practice it may be easier to do everything with a fire and forget DMA

What do you mean "a fire"?

> command queue. Any time you use PIO you're probably going to have to make
> sure the DMA command queue is flushed and the card quiescent before you start
> poking at state.

Sure, and usually, the kernel would arbitrate that.

>
> For linux at least you've already got the DRM/DRI/Mesa kernel/userspace split,
> so I wouldn't expect PIO to gain you anything by way of simplicitly. If you
> want to do anything interesting you're already going to have the DMA queues
> configured.

True.  I'll let the Linux experts deal with that.  My job is to give
them options.

-- 
Timothy Normand Miller
http://www.cse.ohio-state.edu/~millerti
Open Graphics Project