From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <5114E5B2.60507@siemens.com> Date: Fri, 08 Feb 2013 12:46:58 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <5113BFD0.7050501@hilscher.com> <5113D225.8030900@xenomai.org> <5114C05B.7040507@hilscher.com> <5114C302.5020209@xenomai.org> <5114E175.4080908@siemens.com> <5114E30A.2010305@xenomai.org> In-Reply-To: <5114E30A.2010305@xenomai.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Xenomai] Hilscher driver for cifX boards List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: "xenomai@xenomai.org" On 2013-02-08 12:35, Gilles Chanteperdrix wrote: > On 02/08/2013 12:28 PM, Jan Kiszka wrote: >=20 >> On 2013-02-08 10:18, Gilles Chanteperdrix wrote: >>> On 02/08/2013 10:07 AM, St=C3=A9phane LOS wrote: >>> >>>> Le 07/02/2013 17:11, Gilles Chanteperdrix a =C3=A9crit : >>>>> On 02/07/2013 03:53 PM, St=C3=A9phane LOS wrote: >>>>> >>>>>> Hello Sirs, >>>>>> >>>>>> Hilscher is offering a Linux driver based on UIO for cifX boards. >>>>>> >>>>>> In my understanding, down to 1ms cycle time, a PREEMPT RT solution >>>>>> should be enough. >>>>>> >>>>>> The cifX boards can manage with bus cycle times down to 250=C2=B5s= like with >>>>>> EtherCAT or Sercos III firmwares. >>>>>> >>>>>> So it seems in that cases that using Xenomai would be the way to g= o. >>>>>> I suppose that it would be needed to modify or change the existing >>>>>> driver but I can't figure out how things (Xenomai / RTDM / UIO) fi= t >>>>>> together. >>>>>> >>>>>> UIO is the kernel module that allows the mapping of the board memo= ry to >>>>>> user space. >>>>>> >>>>>> The cifX driver uses the libpciaccess to pick up the board and ret= rieve >>>>>> some board information from UIO before the mapping. >>>>>> Then it uses pthread and rt functions when accessing the board. >>>>>> >>>>>> Since UIO and libpciaccess are only used during the initialization= , is >>>>>> it a problem for a Xenomai application ? >>>>>> >>>>>> We have setup a Xenomai system and tried to compile the user land >>>>>> library with Xenomai options and flags and it seems we have been s= uccessful. >>>>>> The driver should be using the POSIX skin of Xenomai if we have be= en lucky. >>>>>> >>>>>> I can't see why we would need RTDM. Any hint please ? >>>>>> >>>>>> I am an absolute beginner in the Xenomai arena, don't throw me to = the >>>>>> lions... >>>>>> >>>>> >>>>> If UIO is used to register an interrupt handler for instance, the >>>>> interrupt handler will not be called in real-time context when used= with >>>>> Xenomai, so, you would have to use the (deprecated) native or posix= skin >>>>> services to register a user-space interrupt handler, or more likely >>>>> write an RTDM driver. On the other hand, if what you need is simply >>>>> accessing the board registers through MMIO, then you do not need RT= DM. >>>>> >>>>> While accessing registers from user-space may be tempting, there is= a >>>>> risk of ending up with an application where the driver code is not >>>>> clearly separated. Writing a driver separated from the application = is >>>>> preferable, as it provides a sane isolation between the two. If you >>>>> change the hardware, you just have to rewrite a driver which follow= s the >>>>> same profile, if you want to write another application using the sa= me >>>>> driver, you can keep the driver. >>>>> >>>> >>>> Thank you for your kind support Gilles. >>>> >>>> The cifX Device Driver is Hilscher's library to deal with cifX board= s=20 >>>> and is available for the major OSes. >>>> Additionally it is available to anybody as source code, the cifX Dri= ver=20 >>>> Toolkit when one has to create a driver for his own OS. >>>> >>>> This driver library accesses the board interface which is a Dual Por= t=20 >>>> Memory. >>>> >>>> So the user application shall use this layer and gets independence f= rom=20 >>>> the target OS. >>>> >>>> I understand that we should create an RTDM driver instead of a UIO=20 >>>> driver and adapt the user library so that it uses the RTDM driver. >>> >>>> >>>> Am I right ? >>> >>> >>> I tried to explain why it may be better to create an RTDM driver, but= in >>> this case this may not be the best option. The answer to your questio= n >>> depends on what you have to do to implement the driver. As I said, if >>> you simply have to access MMIO registers, user-space may be fine, if = you >>> have to handle interrupts kernel-space (so, RTDM) is preferable. >> >> Are we talking about linux/drivers/uio/uio_cif.c here? That one >> obviously has interrupt support. >> >> If your customers may want to use Xenomai 3 with I-pipe instead of >> Preempt-RT underneath (both options will exist), RTDM will still be >> required for interrupt handling. If you like to, you could propose suc= h >> a driver for Xenomai integration. That would ensure it will come with >> future releases. >> >> I also wonder if it didn't make sense for us to provide an UIO-like >> infrastructure for such use cases (single-user device drivers with IRQ >> event channel needs). >=20 >=20 > The native and posix skin provide support for interrupts in user-space.= .. That's deprecated, and UIO is more than this. Jan --=20 Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux