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Re: Raspberry Pi: gpiomem device support

On 4/3/24 18:36, Hank Barta wrote:
I'm not sure if this will help. I explored GPIO on Debian a bit and posted my code at https://github.com/HankB/GPIOD_Debian_Raspberry_Pi <https://github.com/HankB/GPIOD_Debian_Raspberry_Pi>
I have NDI if its usable for you, but linuxcnc for the pi's has a driver module intended for the mesa 7i90HD & similar interface boards, which can be configured for high speed spi interfacing that talks spi over 3 gpio pins, talking to the 7i90HD in 32 bit packets at 42+ megabaud, and gets 32 bit status packets back from the 7i90HD card at 25 megabaud. Been rock solid thru rpi3b/rpi4b's to run by late WW-II vintage 11x54 I converted to lcnc nearly a decade back just to see if I could do it, teaching my old lathe all the new dances that come with linuxcnc. The limits of what it can do today is limited only by your imagination. 
best,
On Wed, Apr 3, 2024 at 12:42 AM Thomas Lehmann <lehmann-56d5e+565@posteo.de <mailto:lehmann-56d5e%2B565@posteo.de>> wrote: 

    Good Day!

    I've tried to get GPIO access working on 1B (Raspberry Pi B+) images
    from [1], however, the "/dev/gpiomem" device is missing and access to
    "/dev/mem" (some libaries fall back to that device) is denied (even as
    root, and I don't even want to use "/dev/mem").

    Searching the internet brough up some udev rules. So I tried thse
    without success:

    SUBSYSTEM=="gpio", GROUP="gpio", MODE="0660"
    KERNEL=="gpiomem", GROUP="gpio", MODE="0660"
    SUBSYSTEM=="bcm2835-gpiomem", GROUP="gpio", MODE="0660"
    SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio",
    MODE="0660"

    I later found /lib/udev/rules.d/60-rpi.gpio-common.rules and added
    these
    rules. Also no success.

    I can't find "gpiomem" in the kernel config.

    In the official Raspberry Pi repository there once was a request [2] to
    enable a kernel config "CONFIG_BCM2835_DEVGPIOMEM". This module was
    apparently replaced by something called "raspberrypi-gpiomem" in commit
    27543eeff4553f5caf7c6d8763c566042b047af0. Interestingly I can't find
    that phrase in any other commit in their repo.

    (Note: I'm aware that Debian does not refer to the Raspberry Pi [2]
    repo, this just came up in my research.)

    To me there seems to be kernel support missing or a config is not set.

    Can someone please clarify on this?


    Thank you.

    Best regards,
    Thomas.



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