gpioirq(4) - NetBSD Manual Pages

GPIOIRQ(4)              NetBSD Kernel Interfaces Manual             GPIOIRQ(4)


NAME

     gpioirq -- Install an interrupt handler on GPIO pins


SYNOPSIS

     gpioirq* at gpio? offset 0 mask 0x1 flag 0x00


DESCRIPTION

     The gpioirq driver attaches an interrupt handler to a one or more GPIO
     pins.

     The base pin number is specified in the kernel configuration file with
     the offset locator.  The mask locator can be 0x01 or greater to indicate
     that more pins should have an interrupt handler attached to them.

     The flag locator specifies the interrupt mode to use:

     0x01      Interrupt on the positive (rising) edge of the pin.

     0x02      Interrupt on the negative (falling) edge of the pin.

     0x04      Interrupt on both edges of the pin.

     0x08      Assert the intrerrupt as long as the pin is high.

     0x10      Assert the interrupt as long as the pin is low.

     Note that the interrupts modes are mutually-exclusive, and exactly one
     interrupt mode must be specified.  These flags correspond to the
     GPIO_INTR mode bits defined in sys/gpio.h.  In addition to the interrupt
     mode, setting 0x1000 in flags will enable the printing of a message to
     the console whenever the interrupt handler is called.

     The offset, mask, and flag locators can also be specified when gpioirq is
     attached at runtime using the GPIOATTACH ioctl(2) on the gpio(4) device.


FILES

     /dev/gpioirqu  GPIOIRQ device unit u file.  The output from this device
                    are three uint8_t bytes every time an interrupt fires.
                    The bytes contain the device unit, pin number and the cur-
                    rent state of the pin.


EXAMPLES

     The following example will output the device unit, pin and the pins cur-
     rent state for pins 4, 5, 6, 7, 8, 9, 10, 11, 12 on gpio0:

           /etc/gpio.conf contains:
           gpio0 attach gpioirq 4 0x1ff 0x04

           or a kernel was compiled to have the same parameters.

           #!/usr/pkg/bin/perl

           $dev = "/dev/gpioirq0";

           sysopen(DEV,$dev,O_RDONLY) || die "sysopen: $!";

           while (sysread(DEV,$b,3)) {
               @v = unpack("CCC",$b);

               print join(',',@v);
               print "\n";
           }



SEE ALSO

     gpio(4), drvctl(8), gpioctl(8)


HISTORY

     The gpioirq driver first appeared in NetBSD 9.0.


AUTHORS

     The gpioirq driver was written by Brad Spencer <brad@anduin.eldar.org>.


BUGS

     When an interrupt fires in most devices there is not any information car-
     ried along in the interrupt as to whether or not the pin is high or low.
     Hence the driver reads the current state of the pin after the interrupt
     has fired and it is possible that the state of the pin could have changed
     between the time the interrupt fired and the reading of the state.  As a
     practical matter the only time the pin state will be reported wrong is if
     there is a very large number of interrupts happening.  The driver could
     have made some assumptions if the interrupt was only for a rising edge or
     falling edge as in those cases it would be possible to know what the pin
     state would have been, but in the case of the double edge, there really
     will not be any way to be sure with most hardware and, in any case, the
     gpio(4) infrastructure does not support getting at that information even
     if it did exist.

     It is important that if the gpioirq(4) device is opened that it be read,
     as it may be possible to run the kernel out of memory if the device is
     opened but not read and interrupts occur on a pin tied to the driver.

NetBSD 10.99                   November 5, 2023                   NetBSD 10.99