[wdmaudiodev] Re: Atomic IO Operations.
- From: Walter Oney <waltoney@xxxxxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Mon, 27 Jan 2003 16:06:20 -0500
Jay Schwichtenberg wrote:
> I have hardware that in certain cases needs to have IO operations done
> atomicly. Mainly in a DPC and in once case at startup. I'm talking at the HW
> level and not the system level. Basicly these operations can not be
> interrupted by anyone not OS, not timer, not keyboard..... A couple examples
> are: programming FPGAs, in a multiple card system being able to write to
> every cards start register without being interrupted to keep them
> synchronized. Now days you can't just do the old pushfd, cli, .... popfd
> which sucks. (There are some of us out here that can write real drivers and
> not abuse the system.) From what I can tell all the spin lock stuff and
> KeSynchronizeExecution just boost the IRQL to beyond the current cards
> level. Maybe I might be wrong.
If your card uses a hardware interrupt, you would want to use either
KeSynchronizeExecution or IoAcquireInterruptSpinLock to serialize access
to your card amongst your ISR and all other parts of your driver. These
functions do *two* things on a multiprocessor system: they raise the
IRQL and they acquire a spin lock associated with your interrupt. While
one cpu holds the spin lock, no other cpu can claim the same lock.
Hence, no other cpu can access your hardware.
--
Walter Oney, Consulting and Training
Basic and Advanced Driver Programming Seminars
Now teaming with John Hyde for USB Device Engineering Seminars
Check out our schedule at http://www.oneysoft.com
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