Re: The Linux Staging tree, what it is and is not.

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> My understanding of an object dictionary is that it is only a structured 
> view to a set of configuration variables, process variables and 
> diagnostic information. It could also be an XML file or a simple C 
> struct. In our implementation the object dictionary is not necessarily 
> the backing store of the data. The process variables for example are 

It's also possible I think to look at the object dictionary as no
different from port numbers. The object identifiers tell you who owns the
data and thus who needs to be told. I admit to being a bit rusty on this.
My last near encounters with fieldbus type systems were some years ago
when I²IT was involved in EMUG and OLCHFA and I managed to keep out of
the blast radius of those ;)

> information of what to copy to where comes from the object dictionary. 
> But it is possible to extract this information from the objdict and pass 
> it via generic structures (e.g. something like IO vectors) to the PDO 
> module in kernel. The information flow of the configuration data is 
> one-way only, from userspace to kernel. This is what I plan to implement 
> in openPOWERLINK, because the copy information can also be passed to a 
> special hardware like a DMA controller.

Ok so your hardware in fact really is oriented around an mmap type
interface ?

Alan