First of all, thank you for your quick answer ! >> I am a newbie in RTNET and i have questions. I have to program a >> specific >> MAC protocol for interacting, over an ethernet bus, with hardware >> specific >> distributed units that implement this protocol. Since these units just >> have a MAC and an Application Layers, i have to reproduce this network >> stack on the PC side, that's why i don't want to use any IP layer on top >> of my MAC layer. The MAC Layer will be included in a real-time task >> running in kernel space (mandatory in the control architecture i am >> developing). > > And the application layer? Will it be real-time as well, or standard > Linux?
Yes, the application layer will also be real-time. >> - If no, can i use, by any way, libpcap in hard real-time RTAI tasks in >> combination with RTNET ? If yes, How should i proceed ? >> - If no, does RTnet provide functions like the ones provided by libpcap >> ? >> If yes, where could I find documentation/examples on these functions ? > > RTnet's RTcap layer provides the low-end interface for libpcap to sniff > also on with real-time interfaces. But in this case the capturing > front-end remains non-RT. Would this be OK for you? I am not sure, but i think "no". A module implementing a MAC layer has to be implemented as a "complete" real-time task. Indeed, a MAC module will have the highest priority in my multi-tasks architecture because it needs to preempt all other real-time tasks. So if "the capturing front-end remains non-RT" means that the corredponding MAC module (that calls this front-end) will be executed in user space (and so, if i don't make a mistake, can be preempted by my other real-time tasks), it's not good for me. > I still have problems understanding your scenario, thus I'm careful with > pointing at certain design paths. It basically depends on > > a) the real-time requirements of your components To sum up quickly, my Application and Mac Layers put in place communication with hardware distributed units and standardize access to these heterogeneous units. The main idea is to build a kind of generic middleware that can be "adapted" according to 1) the type of the communication media used (e.g. Ethernet in the frame of our discution), 2) the MAC Layers used to manage communications on these media (one for a given network) and 3) the Application layers used to manage communication with the distributed units (one for each type of units). On top of that middleware, there are several "hardware independant" real-time modules (managing control, and perception activities) that communicate in a transparent way with units. All modules need to be "real-time" because i need to manage precisely task preemption in my control architecture and because the overall dynamics of the system imposes to limit the "cost" of context change (far to high in user mode). > b) the programming model (single application/multiple apps, user/kernel > space) - Multiple applications: i am programming a generic framework that can be specialized for different applications in the same business domain. - Kernel space only: all modules (MAC modules, Application layer module, control modules) have to be implemented with kernel space tasks. So, what i need is the simplest API(s ?) to capture and send Ethernet packets, but also to handle IRQ comming from Ethernet boards, without leaving the kernel space. Does RTCap satisfy all my wishes ? Can I use it directly without using all other (unecessary for me) RTNet functionnalities ? Robin ------------------------------------------------------------------------- SF.Net email is sponsored by: Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ RTnet-users mailing list RTnet-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/rtnet-users
