Li Yi (Adam) wrote: > Hi Jan, > > Quick questions: ...long answer. ;)
> 1. What is the problem with "xntimer_init()"? The timerbench.c use it to > create timers? You are going to write a RTDM implementation? Not an implementation but rather a thin wrapper. The aim of RTDM is to remain independent of the actual RT-Linux implementation. We already have RTDM support in recent RTAI, the future may bring ports to RTLinux/GPL (as long as this project keeps alive) and preempt-rt. Sebastian's SJA1000 CAN driver is e.g. RTDM-based and can be recompiled for RTAI without using tons of #ifdefs. RTnet does this even longer. So, by using Xenomai nucleus services directly you make your driver harder to port. The timerbench-way is only an intermediate solution until we have a real abstraction (see also comments in the code). > 2. What is general program model for Xenomai application like data > acquisition? What I am thinking is to start the RT task in user space (via > POSIX skin), and implement the read funtion in kernel space using RTDM. Unless you have specific requirements, putting the (common) hardware interface into an RTDM driver and leaving the rest to the application is the preferred way (it's nothing Xenomai-specific, is it?). If a RTDM driver always has to be in kernel space is a different question. I have some weird ideas about (widely) seamless user space migration (and vice versa), either into the process context of an exclusive device user (kind of library) or even shared between multiple processes (device servers, microkernel-like, probably at similar costs). Anyway, the goal is to keep the RTDM interfaces for both domains widely identical, and this will require some more work (and thus time, which I'm always lacking). Userspace drivers are not the ultimate answer to all questions (that's 42 anyway), but they can open certain new possibilities, both technically and legally. Jan
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