Re: [Xenomai-help] Reading Memory Mapped IO

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Doyle, Alan wrote:
 > 
 > Hi,
 > 
 > I have an application where I need to read four contiguous memory mapped
 > data registers in response to an interrupt. As its real time critical I
 > intend to implement the read in Xenomai. Having read and processed the
 > data it later needs to be passed to a Linux domain application, I am
 > hoping to use a Posix message queue for this purpose.
 > 
 > I seem to have two options as to how to implement this, I could register
 > the interrupt in a Xenomai user space thread and mmap the data registers
 > so that on receiving the interrupt the registers could be read.
 > Alternatively I could write a Xenomai RTDM driver to read the registers
 > on interrupt and use the driver read call from the Xenomai user space
 > thread to access register data. In each case the data would then be
 > passed to the Linux domain via a message to a Posix queue - after some
 > further processing that is not real time critical.
 > 
 > Could you enlighten me as to the pros and cons of each approach,

The advantage of the "all in user-space" approach is that you will be
able to get rapidly something that works, because debugging in
user-space is much easier than in kernel-space. On the other
hand, writing a driver using RTDM will result in a clear separation
between application code and driver code that will be easier to maintain
on the long run. Imagine what will happen in the two cases when the
hardware changes.

-- 


					    Gilles Chanteperdrix.