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[OMAP35x] How to add a GPIO Sysfs Interface for Userspace

GrantHatamosa
Expert 1930 points


Hi,

We are using AM35x-OMAP35x-PSP 03.00.01.06 and I'd like to create a userspace interface to three GPIOs.

Can someone please point me to the Linux source code where I can indicate which GPIO to create a userpsace interface?

I see that gpio.c in plat-omap initializes most GPIOs but I can't figure out which part/structure to modify.

 

  • 0
    Guru 26430 points

    In theory, your Linux kernel already supports a userspace interface to any GPIO. Search for "/sys/class/gpio" in this forum or on the internet. The GPIO capabilities of your specific kernel is in the kernel source at "Documentation/gpio.txt". The latest kernels also have edge detection. Check that the GPIO file system is enabled in the kernel configuration. It will be CONFIG_GPIO_SYSFS in your config file. Under menu config it will be called "/sys/class/gpio/... (sysfs interface)". Example commands for configuring, toggling GPIO 11.

    cd /sys/class/gpio/
    echo 11 > export
    cd gpio11
    echo out > direction
    echo 0 > value
    echo 1 > value
    echo 0 > value

    You might have configure the MUX to make a particular pin into a GPIO. That might be done is u-boot or might be done in linux. Depends on your situation.

  • 0 in reply to Norman Wong
    Expert 1930 points

    thank you for that. that's exactly what i need.