Re: [Xenomai-help] Deprecated kernel system calls in xenomai-head and new application development paradigm

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

Rus V. Brushkoff wrote:
> On Wed, 2 Sep 2009, Philippe Gerum wrote:
> 
> :>  Next - I do not 
> :> understand why the previous model lets the _developer_ itself decide 
> :> which of the application tasks will be running in kernel and which will 
> :> be running in user space. The current model left the people without any 
> :> choice. So the current model itself decided instead of developer what is 
> :> better - I think this is wrong.
> :
> :With that kind of reasoning, you would keep on coding your RT
> :application fully in kernel space, but we made some progress since 1997,
> :fortunately.
> 
>  Sorry, but device drivers for hardware that need RT processing can't be 
> written in user space. Dealing with interrupts, PCI, DMA, I/O ports can 
> be done only in kernel space. So it is not possible to decide at the 
> Xenomai architect level wich driver task are optimal to run in which mode 
> - it will depends from the particular development problem area.
>  So I think that forcing people to write the RT tasks only in user space 
> will make unneded latencies, which will be inserted by data passing 
> between user and kernel domains.
>  Next: the traditional and clean Unix programming concept suppose that 
> user space applications are simple and operate on the files/pipes that 
> are attached to kernel drivers. It will be better to leave this concept 
> live as it proved its architect efficiency.

You misunderstand us. We tell you that you should develop drivers in
kernel-space, using the RTDM skin. The RTDM skin is made to resemble the
Linux driver model, so that it will make your drivers easily portable to
vanilla linux.


-- 
                                          Gilles