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Re: MMIO regions
James Simmons wrote:
>
> Howdy again!!
>
> I noticed something for SMP machines with all the dicussion about
> concurrent access to memory regions. What happens when you have two
> processes that have both mmapped the same MMIO region for some card.
> Doesn't have to be a video card,. On a SMP machine it is possible that
> both processes could access the same region at the same time. This could
> cause the card to go into a indeterminate state. Even lock the machine.
> Does their exist a way to handle this? Also some cards have mulitple MMIO
> regions. What if a process mmaps one MMIO region of this card and another
> process mmaps another MMIO region of this card. Now process one could
> alter the card in such a way it could effect the results that process two
> is expecting. How is this dealt with? Is it dealt with? If not what would
> be a good way to handle this?
AFAIK no drivers except fbcon drivers map any IO-region to userspace.
//Marcus
--
-------------------------------+------------------------------------
Marcus Sundberg | http://www.stacken.kth.se/~mackan/
Royal Institute of Technology | Phone: +46 707 295404
Stockholm, Sweden | E-Mail: mackan@stacken.kth.se
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