Re: [Xenomai-help] How to avoid a tight real time loop

[Daniele Nicolodi <daniele@domain.hid>]

On 16/06/10 00:11, Alexis Berlemont wrote:
>> There is not an analogy API that can be used to require a certain amount
>> of data to the ADC driver. How can I code this loop to let other
>> processes to run?
> 
> As a matter of fact, there is something in the API which could have
> helped you in an unmapped configuration. If you set the flag
> A4L_CMD_BULK in the field "flags" of the command structure, a call to
> a4l_async_read() only returns when the data size specified as argument
> is available.

Unfortunately copying memory data around would decrease too much the
performance of my data acquisition code. By the way, I think that using
the O_NONBLOCK fcntl flag on the device descriptor file descriptor would
be the best way to activate this feature.

> Unfortunately, I have not done the same thing with a4l_poll, I might
> have added the requested size as an additional argument to a4l_poll. 
> 
> Any idea on how to extend the API without breaking it ?

I do not see any way rather than augmenting the function signature with
an additional parameter. If you want to maintain API compatibility the
only thing to do is to add a different function.

Cheers,
-- 
Daniele