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Linux Based IOC Support EPICS Meeting at BESSY

Linux Based IOC Support EPICS Meeting at BESSY. May 2002 Marty Kraimer. VISION. LINUX REPLACES VXWORKS BUT: Linux isn’t a real time operating system Non-preemptive kernel => no context switch while kernel active. Interrupts can be disabled for long periods of time.

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Linux Based IOC Support EPICS Meeting at BESSY

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  1. Linux Based IOC SupportEPICS Meeting at BESSY May 2002 Marty Kraimer

  2. VISION • LINUX REPLACES VXWORKS • BUT: Linux isn’t a real time operating system • Non-preemptive kernel => no context switch while kernel active. • Interrupts can be disabled for long periods of time. • Worst case can be 100s milliseconds. • Future • Development kernel is preemptive. • Work in progress so that interrupts disabled for short times. • Other possibilities • RTLinux • RTAI

  3. Modified Vision • Existing Linux good enough for some Applications. • 2.6 Kernel will be good enough for additional Apps. • Often small part of App has stricter real time. requirements. In this case consider RTLinux/RTAI. • For demanding Apps use RTEMS or stay with vxWorks.

  4. Near Term Goals • Industry Pack Support on Linux IOCs • Work with Tim Mooney’s group • Joe Sullivan working on PCI based motor support. • IP + Motor => usable for some beam line applications. • Expect there will be a lot of interest.

  5. Progress • PCI-40A : SBS Quad IP Carrier for PCI Bus • Linux Kernel support now exists for • Generic IP carrier support (Like ANJs IPAC support) • PCI-40A • IP-488 (Green Springs GPIB IP using the ti9914) • EPICS Gpib driver • Implements Benjamin Franksen’s interface • Talks via file system to IP488 Linux driver • DG535 support works (For awhile before crashing) • Message Passing Facility MPF ported to 3.14 • Lots of cleanup. • Ran several tests successfully

  6. Still to do • IP Serial • IP330 (ADC) • DAC128V (DAC) • ipUnidig (Digital I/O) • BIG ISSUE • Existing support allows MPF support to register with interrupt routine, i.e. user code called directly by interrupt routine. • IP330 allows floating point in interrupt routine. • Initial Strategy • Extract interrupt handlers and use insmod to put them in kernel • Convert floating point to integer.

  7. Additional Tasks • Allow user level to access IP register space. • Have written but not tested. • Is this better than kernel drivers? • What about interrupts? • Work with Tim’s group to support synapps on Linux • APS/ASD can also use Linux IP support. • Many many records for serial I/O. • Quite a few using IP330. • Monitoring Only and not time critical • Future hardware??? PC*MIP, etc, etc.

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