How to design non blocking device drivers?

On Thu, 18 Sep 2008 06:54:59 -0700, ssubbarayan wrote:

> Hi all,
>      I would like to understand how to design drivers in such a way
> that its non blocking?
> 
> To be more specific,If suppose I have an EEPROM device and two tasks are
> trying to write some data to the EEPROM device,generally what happens
> is,we will have a semaphore inside driver so that till one task
> completes using the device,the other task will be pending to complete
> the writing.What would be the way to design the driver in such a way
> that the second task mentioned above does not go into blocking,but still
> completes writing to the EEPROM.
> 
> Sorry if this query looks naive,I am trying to think on alternatives for
> one our product.Application is a thirdparty application which needs this
> requirement.
> 
> Looking farward for your thoughts and advanced thanks for the same,
> 
> Regards,
> s.subbarayan

The EEPROM is, itself, blocking (you can't initiate a write while it's 
writing), so a driver for it is either going to reflect that, or you're 
going to have to mirror the EEPROM and schedule writes.

So your choice is blocking, or a fairly complex shadowing scheme.

-- 
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html