Hi Wolfgang, Wolfgang Grandegger wrote: > Hi Matthias, > > Matthias Fuchs wrote: >> Hi Wolfgang, >> >> Wolfgang Grandegger wrote: >>> You have to define the real CAN system clock, which is 16/2 = 8 Mhz for >>> most SJA 1000 hardware even if the oscillator is running at 16 MHz. I >>> will add some reasonable note to rtcan_dev.h >> Is there any special reason for this? Wouldn't it be more meaningful >> to pass the SJA1000 externally applied clock frequency? I can imagine >> that others will also run into this issue as Jan and I did yesterday ;-) > > The frequency is used to calculate reasonable bit-timing parameters, not > only for SJA 1000. It's used in a similar way in the Linux socket CAN > driver. I am not very familiar with the socket CAN driver, but after a quick glance at its svn repository it seems to me that they are also passing the SJA1000 external clock frequency to the module (clk-parameter).
So I think other controller's drivers may use an other meaning of the clk/clock parameter. But for SJA1000 the ext. clock frequency is best. > >>>> Then we will soon have to discuss how to deal with a rtcan_isa >>>> derivative that uses ioremapped memory instead of ports (naming, >>>> separation or integration). >>> We could add a generic device similar to ISA (or extend ISA >>> accordingly). >> The SJA1000 isa driver is very simple - and so is the modified version >> for the memory mapped SJA1000. I think that merging both ways of >> access to the SJA1000 into a single driver will make the code much >> more dirty. I would prefer different source files (= different drivers). > > I agree. > >> It would be a compromise to add support for boards that use some kind >> of indirect addressing to access the SJA1000 (address + data register) >> into the isa and mem versions of the driver. > > Fine if this could be done in a generic way. We also should add a > generic PCI driver sooner than later. > >> One more proposal: I think many (old) ISA drivers name the module >> parameter for the ISA io port "io" instead of "isa". For the memory >> mapped SJA1000 driver, I'd like to call the parameter "mem". > > Well, I cannot remember why I used the name "isa". Common is "io" or > "port" or "ioport", indeed. "io" and "mem" or "ioport" and "iomem" would > be fine for me. I will use mem for the mem'mapped driver. The socket CAN project uses base_addr - they must have an affection to a long parameter name :-) Matthias _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
