Re: [Xenomai-help] migration scenario to xenomai

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

Guenter Ebermann wrote:
> Hi Gilles,
> 
> Am 07.08.2010 um 09:46 schrieb Gilles Chanteperdrix:
>> You can access hardware registers in user-space by mmaping the memory
>> mapped ones with /dev/mem, or using iopl/ioperm and in[lwb]/out[lwb] for
>> the old x86 I/O registers.
> 
> Ok, thank you very much. I will look into using /dev/mem (we dont need x86 I/O
> - we use powerpc arch).
> 
>> However, if this can help for a first order port to Xenomai,
>> implementing an RTDM driver later is better on the long run. By limiting
>> the interface between the application and low-level code to a well
>> defined interface, it will make it possible to use different
>> applications with the same drivers, or use different hardware with the
>> same application at will, things that are often hard when the low-level
>> code is mixed with the application code.
> 
> The xenomai RTDM API is made solely for kernel space, if i understood the docs
> correctly?
> 
> Yeah, I understand your point with generic interface and device driver
> separation. And I really like the way this happens under linux/xenomai. I am
> also willing to write new drivers which are usable by a broader public using
> these design principles. But the communication stack I am gona use (AUTOSAR
> FlexRay stack) does not follow them. AUTOSAR (www.autosar.org) specs defines
> the Interfaces and layers of the whole communcation system for cars. It does
> not involve kernel/userspace separation, but it also does not mix the low-level
> code with application code. Low level code is only implemented in the device
> drivers (CAN, LIN, FlexRay), but the interface to the upper level stack is not
> generic (as in linux with device drivers) - it is different for each kind of
> lower layer device (CAN, LIN, FlexRay) to gain the best performance from each
> of them.

Well, it looks to me like you can implement the interface between driver
and user-space with standard posix interface (especially ioctl), and
then implement the AUTOSAR interfaces as a user-space library relying on
this posix interface.

-- 
					    Gilles.