Re: [Xenomai-core] Future of Xenomai's RTDM driver repository
Philippe Gerum wrote: Hi Wolfgang, First of all, thx for the CAN stack. Great job. On Thu, 2006-08-03 at 09:58 +0200, Wolfgang Grandegger wrote: Jan Kiszka wrote: snip Now I would suggest to look at RTCAN (or what it will be called in the end) and to discuss on this first concrete example how we can proceed towards the sketched goal. Looking forward to your feedback! As you have said, maintaining a RTDM driver within the Xenomai repository clearly has some advantages but it also puts more burden onto the Xenomai maintainers and some developers might even prefer to keep thing separated. Therefore I suggest a simple RTDM add-on framework to support external RTDM drivers as well. They could be announced and listed on the Xenomai home page and then it would alsl be visible that there is a FireWire stack for Xenomai. What I had first was a add-rtdm-driver.sh, a modified version of Philippe's prepare-kernel.sh script, to add the RTDM driver to the kernel tree. Similarly, as script could be used to add loosely the driver to Xenomai. What do you think? I can't speak for Jan wrt providing a RTDM add-on framework, but since Xenomai is currently the reference platform for RTDM (at least, the real-time infrastructure over which most of this work is experimented, debugged and stabilized), I would rather seek integration of RTDM-based drivers into the Xenomai tree, instead of a complete separation. I understood that Jan also prefers driver integration into Xenomai. Just for some big external package like RTnet, an add-on would be nice to benefit from the Xenomai infrastructure (static linking, etc.). The reason being that it makes sense (to a Xenomai maintainer, that is) to reduce the odds of discrepancies between the core real-time framework, the driver infrastructure and the client drivers, at least while the first two are undergoing a rapid evolution. The same in-tree vs out-of-tree drivers maintenance dilema which is known from the kernel folks will also apply to us, if RTDM, and/or RTDM over Xenomai are as successful as we wish, i.e. creating opportunities to provide lots of RT drivers sharing a common infrastructure. Said differently, the day a significant number of people will start relying on a rich collection of RTDM-based drivers over Xenomai, we _will_ have maintenance issues to deal with, anyway, starting with answering a lot of questions on xenomai-whatever*. In such a case, I'd rather reduce the odds of integration issues between Xenomai-RTDM and/or RTDM/drivers. This said, I'm not saying that Xenomai should be the only RTDM-based driver repository in the long run; but I'm arguing that Xenomai could be used as a centripetal force to help developing and stabilizing the RT driver ecosystem around RTDM. OK, I can follow your arguments. It's fine for me. Thanks. Wolfgang. ___ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
Re: [Xenomai-core] Future of Xenomai's RTDM driver repository
Jan Kiszka wrote: Hi, instead of replying directly to Wolfgang's announcement of their great CAN stack I take the chance to start a generic thread on the future of RTDM drivers *within* Xenomai. If you look at the real-time Linux scene now and in the past, you may find it fairly scattered. Specifically precious Open Source drivers are hard to find, not always up-to-date, or not ported to your favourite kernel/RT-patch. Just check how many CAN driver projects for how many RT APIs are out there. There are even a few hardware vendors providing driver packages for real-time Linux, others offer at least some kind of reference code, but many nothing at all. Sad but true for _many_ years. RTDM came into play to provide a common ground for real-time driver development under Linux. It is already utilised by quite a few stand-alone driver projects and even vendor drivers. But as resources are limited, maintenance is tricky, and testers are rare, we should consider concentrating driver development efforts more intensively. I'm convinced such concentration should primarily happen within the Xenomai driver repository. Xenomai has the unique potential to provide a real-time framework for both the co-scheduling approach and for the native RT-Linux environment that Preempt-RT will probably push into mainline one day. And Xenomai is also a sound foundation for the tricky 2.4/2.6 support scenario. Here are the concrete advantages I see in maintaining drivers *inside* Xenomai: o Better visibility (did you know that there is a working FireWire stack for Xenomai?) o Better testing, also across architectures, due to more users (this applies to the drivers, but also to RTDM and Xenomai in all) o Closer to the latest RTDM development o Wrapping environments for changing kernel interfaces (2.4/2.6 etc.) o In-kernel build o Simpler build system (look at RTnet...) o Single, integrated package, thus less breakages due to version mismatches Of course, there are also certain critical topics that need to be resolved first: o Clear acceptance rules - Maintenance commitment: dump-and-run will not scale. Unless there is already a community behind it, complex drivers need people to look after them. Dead/unused drivers should get moved in some corner after a while. - Coding style: Should simply be kernel style (though I personally hate tabs). - Documentation: New RTDM profiles as well as the drivers themselves must contain some words (surely a more softish requirement). - Test cases, test conformance: Drivers should provide some simple tests or, if once available, conform to existing tests for their RTDM profiles. o Repository organisation - Where to keep utilities (Wolfgang raised this as well)? Should a rtcanconfig come with Xenomai, as a separate package of rt-utils, or as package of its own? - Where to put test cases? Distribute them separately? - Where to collect usage examples? This is actually a generic question, also for the skins (I think the current situation is a bit unsatisfactory). o Support organisation Simple drivers can certainly be managed via xenomai-help, existing communities will continue to use their own forums, but what about new subsystems? I could imagine introducing some [EMAIL PROTECTED] lists for them, Philippe suggested simply xenomai-drivers which is likely already sufficient. Now I would suggest to look at RTCAN (or what it will be called in the end) and to discuss on this first concrete example how we can proceed towards the sketched goal. Looking forward to your feedback! As you have said, maintaining a RTDM driver within the Xenomai repository clearly has some advantages but it also puts more burden onto the Xenomai maintainers and some developers might even prefer to keep thing separated. Therefore I suggest a simple RTDM add-on framework to support external RTDM drivers as well. They could be announced and listed on the Xenomai home page and then it would alsl be visible that there is a FireWire stack for Xenomai. What I had first was a add-rtdm-driver.sh, a modified version of Philippe's prepare-kernel.sh script, to add the RTDM driver to the kernel tree. Similarly, as script could be used to add loosely the driver to Xenomai. What do you think? Wolfgang. ___ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
Re: [Xenomai-core] Future of Xenomai's RTDM driver repository
Wolfgang Grandegger wrote: Jan Kiszka wrote: Hi, instead of replying directly to Wolfgang's announcement of their great CAN stack I take the chance to start a generic thread on the future of RTDM drivers *within* Xenomai. If you look at the real-time Linux scene now and in the past, you may find it fairly scattered. Specifically precious Open Source drivers are hard to find, not always up-to-date, or not ported to your favourite kernel/RT-patch. Just check how many CAN driver projects for how many RT APIs are out there. There are even a few hardware vendors providing driver packages for real-time Linux, others offer at least some kind of reference code, but many nothing at all. Sad but true for _many_ years. RTDM came into play to provide a common ground for real-time driver development under Linux. It is already utilised by quite a few stand-alone driver projects and even vendor drivers. But as resources are limited, maintenance is tricky, and testers are rare, we should consider concentrating driver development efforts more intensively. I'm convinced such concentration should primarily happen within the Xenomai driver repository. Xenomai has the unique potential to provide a real-time framework for both the co-scheduling approach and for the native RT-Linux environment that Preempt-RT will probably push into mainline one day. And Xenomai is also a sound foundation for the tricky 2.4/2.6 support scenario. Here are the concrete advantages I see in maintaining drivers *inside* Xenomai: o Better visibility (did you know that there is a working FireWire stack for Xenomai?) o Better testing, also across architectures, due to more users (this applies to the drivers, but also to RTDM and Xenomai in all) o Closer to the latest RTDM development o Wrapping environments for changing kernel interfaces (2.4/2.6 etc.) o In-kernel build o Simpler build system (look at RTnet...) o Single, integrated package, thus less breakages due to version mismatches Of course, there are also certain critical topics that need to be resolved first: o Clear acceptance rules - Maintenance commitment: dump-and-run will not scale. Unless there is already a community behind it, complex drivers need people to look after them. Dead/unused drivers should get moved in some corner after a while. - Coding style: Should simply be kernel style (though I personally hate tabs). - Documentation: New RTDM profiles as well as the drivers themselves must contain some words (surely a more softish requirement). - Test cases, test conformance: Drivers should provide some simple tests or, if once available, conform to existing tests for their RTDM profiles. o Repository organisation - Where to keep utilities (Wolfgang raised this as well)? Should a rtcanconfig come with Xenomai, as a separate package of rt-utils, or as package of its own? - Where to put test cases? Distribute them separately? - Where to collect usage examples? This is actually a generic question, also for the skins (I think the current situation is a bit unsatisfactory). o Support organisation Simple drivers can certainly be managed via xenomai-help, existing communities will continue to use their own forums, but what about new subsystems? I could imagine introducing some [EMAIL PROTECTED] lists for them, Philippe suggested simply xenomai-drivers which is likely already sufficient. Now I would suggest to look at RTCAN (or what it will be called in the end) and to discuss on this first concrete example how we can proceed towards the sketched goal. Looking forward to your feedback! As you have said, maintaining a RTDM driver within the Xenomai repository clearly has some advantages but it also puts more burden onto the Xenomai maintainers and some developers might even prefer to keep thing separated. Therefore I suggest a simple RTDM add-on framework to support external RTDM drivers as well. They could be announced and listed on the Xenomai home page and then it would alsl be visible that there is a FireWire stack for Xenomai. Yes, this way still remains open. RTnet, e.g., would be a candidate to remain separate for a while or even longer. OTOH, if you look at the relation between RT-Firewire and RTnet (RTnet requires RT-Firewire to build its rt_eth1394 driver), you can see that this can quickly become complicated, specifically from the build system POV. Or think about some comedi driver for an USB DAQ that may want to work over USB4RT in the future... What I had first was a add-rtdm-driver.sh, a modified version of Philippe's prepare-kernel.sh script, to add the RTDM driver to the kernel tree. Similarly, as script could be used to add loosely the driver to Xenomai. This is something we could consider, but it is feasible only for the plain drivers (no utils
Re: [Xenomai-core] Future of Xenomai's RTDM driver repository
On Wed, 2006-08-02 at 12:19 +0200, Jan Kiszka wrote: Hi, instead of replying directly to Wolfgang's announcement of their great CAN stack I take the chance to start a generic thread on the future of RTDM drivers *within* Xenomai. If you look at the real-time Linux scene now and in the past, you may find it fairly scattered. Specifically precious Open Source drivers are hard to find, not always up-to-date, or not ported to your favourite kernel/RT-patch. Just check how many CAN driver projects for how many RT APIs are out there. There are even a few hardware vendors providing driver packages for real-time Linux, others offer at least some kind of reference code, but many nothing at all. Sad but true for _many_ years. RTDM came into play to provide a common ground for real-time driver development under Linux. It is already utilised by quite a few stand-alone driver projects and even vendor drivers. But as resources are limited, maintenance is tricky, and testers are rare, we should consider concentrating driver development efforts more intensively. I'm convinced such concentration should primarily happen within the Xenomai driver repository. Xenomai has the unique potential to provide a real-time framework for both the co-scheduling approach and for the native RT-Linux environment that Preempt-RT will probably push into mainline one day. And Xenomai is also a sound foundation for the tricky 2.4/2.6 support scenario. Here are the concrete advantages I see in maintaining drivers *inside* Xenomai: o Better visibility (did you know that there is a working FireWire stack for Xenomai?) o Better testing, also across architectures, due to more users (this applies to the drivers, but also to RTDM and Xenomai in all) o Closer to the latest RTDM development o Wrapping environments for changing kernel interfaces (2.4/2.6 etc.) o In-kernel build o Simpler build system (look at RTnet...) o Single, integrated package, thus less breakages due to version mismatches And above all, integration is the key issue, which includes device drivers. This has a maintenance cost, but much lower than breakages due to endemic discrepancies between the out-of-tree modules (whatever modules means here) and the core framework. Of course, there are also certain critical topics that need to be resolved first: o Clear acceptance rules - Maintenance commitment: dump-and-run will not scale. Unless there is already a community behind it, complex drivers need people to look after them. Dead/unused drivers should get moved in some corner after a while. It's the common Xenomai policy since day #1 (i.e. no dead/unmaintained code), so there should be no problem keeping it this way, provided this policy is explicitely stated. However, finding committed contributors will always be the main issue. - Coding style: Should simply be kernel style (though I personally hate tabs). So do I, but fact is that implementing anything else than the strict kernel coding guidelines for kernel-based code raises the barrier on reviewing and even acceptance from the kernel people, so there is no need to fight for such details, imho. This is kernel code, let's use kernel coding conventions. - Documentation: New RTDM profiles as well as the drivers themselves must contain some words (surely a more softish requirement). - Test cases, test conformance: Drivers should provide some simple tests or, if once available, conform to existing tests for their RTDM profiles. o Repository organisation - Where to keep utilities (Wolfgang raised this as well)? Should a rtcanconfig come with Xenomai, as a separate package of rt-utils, or as package of its own? I tend to think that self-contained packages are always simpler to deal with from the user standpoint, therefore CAN utilities should be part of the CAN driver package. Regarding any rtdriverconfig script, maybe we could extend xeno-config in the future to accept external configuration frags, so that we keep a single front-end which would accept additional options dynamically, but this should not be a requirement ATM. - Where to put test cases? Distribute them separately? - Where to collect usage examples? This is actually a generic question, also for the skins (I think the current situation is a bit unsatisfactory). Test cases and usage examples do not usually belong to any particular Xenomai/driver version, so they should be gathered in a separate package. This would also allow to enrich them with end-user contributions with lower constraints on coding style etc. o Support organisation Simple drivers can certainly be managed via xenomai-help, existing communities will continue to use their own forums, but what about new subsystems? I could imagine introducing some [EMAIL PROTECTED] lists for them, Philippe
Re: [Xenomai-core] Future of Xenomai's RTDM driver repository
Hi Wolfgang, First of all, thx for the CAN stack. Great job. On Thu, 2006-08-03 at 09:58 +0200, Wolfgang Grandegger wrote: Jan Kiszka wrote: snip Now I would suggest to look at RTCAN (or what it will be called in the end) and to discuss on this first concrete example how we can proceed towards the sketched goal. Looking forward to your feedback! As you have said, maintaining a RTDM driver within the Xenomai repository clearly has some advantages but it also puts more burden onto the Xenomai maintainers and some developers might even prefer to keep thing separated. Therefore I suggest a simple RTDM add-on framework to support external RTDM drivers as well. They could be announced and listed on the Xenomai home page and then it would alsl be visible that there is a FireWire stack for Xenomai. What I had first was a add-rtdm-driver.sh, a modified version of Philippe's prepare-kernel.sh script, to add the RTDM driver to the kernel tree. Similarly, as script could be used to add loosely the driver to Xenomai. What do you think? I can't speak for Jan wrt providing a RTDM add-on framework, but since Xenomai is currently the reference platform for RTDM (at least, the real-time infrastructure over which most of this work is experimented, debugged and stabilized), I would rather seek integration of RTDM-based drivers into the Xenomai tree, instead of a complete separation. The reason being that it makes sense (to a Xenomai maintainer, that is) to reduce the odds of discrepancies between the core real-time framework, the driver infrastructure and the client drivers, at least while the first two are undergoing a rapid evolution. The same in-tree vs out-of-tree drivers maintenance dilema which is known from the kernel folks will also apply to us, if RTDM, and/or RTDM over Xenomai are as successful as we wish, i.e. creating opportunities to provide lots of RT drivers sharing a common infrastructure. Said differently, the day a significant number of people will start relying on a rich collection of RTDM-based drivers over Xenomai, we _will_ have maintenance issues to deal with, anyway, starting with answering a lot of questions on xenomai-whatever*. In such a case, I'd rather reduce the odds of integration issues between Xenomai-RTDM and/or RTDM/drivers. This said, I'm not saying that Xenomai should be the only RTDM-based driver repository in the long run; but I'm arguing that Xenomai could be used as a centripetal force to help developing and stabilizing the RT driver ecosystem around RTDM. -- Philippe. ___ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
