[ECOS] Implementing callback from driver to application

[Mike Sweeney]

On 8/5/07, Gary Thomas <gary@mlbassoc.com> wrote:
> Mike Sweeney wrote:
> > I have a custom device driver that needs to invoke a callback function
> > that is registered by the user's application. I have a 3 level
> > interrupt service mechanism within my device driver: an ISR, a DSR,
> > and an interrupt service thread. Basically in my interrupt service
> > thread I invoke the callback function. This is not a great design
> > because I don't want to be blocked in my interrupt service thread for
> > an unknown amount of time. I may have multiple application callbacks
> > to invoke depending on the device status.
> >
> > I'm looking for some input on how best to tackle this within eCos. My
> > design requires the kernel so I can use any sort of kernel services
> > and am not restricting myself to the driver API. Should my driver have
> > another dedicated thread that receives mailbox messages from my
> > interrupt service thread and then calls the callbacks from within its
> > own context? All ideas are appreciated.
>
> Yes, this is the preferred method (threads are quite cheap).
> Your driver thread can then call back into the user code, block,
> etc, without affecting the rest of the system.
>
> Note: a good usage example of this is the input processing
> thread in the FreeBSD networking stack.
>

Thanks Gary. I'll check out the code you mentioned.

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