It depends what you want to achieve. In any aspects, polling is not a
good idea for driver anyway.
You may want to send a message from driver when something in driver
occurs, and setup your application to listen that message. After
user-mode application receive the message, then you can call your
function in the user space and/or use IOCTL for what you really want
to do.
On 4/9/07, AsHwAtH <itsmeash@xxxxxxxxx> wrote:
> Ok, Thank you for the suggestion.
>
> But how are callbacks really implemented then?
> If I keep calling DeviceIOControl from my application(like polling), it
> drains CPU usage.
>
>
>
>
> On 4/9/07, Eugene Muzychenko <emuzychenko@xxxxxxxxx> wrote:
> > Hello AsHwAtH,
> >
> > > From my application I am passing the address of the User defined
> function to
> > > the driver through my own IOCTL call.
> > > I store this address in the driver as a function pointer and call it
> when a
> > > particular condition is met inside the MSVAD.
> >
> > Before trying to develop (and even modify) a kernel-mode driver, you
> > must clearly understand the differences between user and kernel
> > execution modes, address space, thread contexts etc. Your attempt to
> > directly call a user-mode function from the kernel-mode driver means
> > that you have almost no such knowledge. In this situation, your work
> > will be very inefficient, resulting many incorrect solutions.
> >
> > Your driver could inject some code into a requesting
> > process, create an auxiliary thread that will watch for some event
> > signaled by the driver and call a specified function. But it will be
> > very complex for you to implement. So a simplest way is to create a
> > thread from your application and not to pass function address to the
> > driver.
> >
> > Regards,
> > Eugene
> >
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>
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