IBM OCP GPIO driver for linux 2.6

[Dale Farnsworth]

In article <1154603751.17247.10.camel at jb-portable> you write:
> I'm porting a custom PPC 405GP card based on a Walnut from Montavista
> Linux 3.0 (kernel 2.4.18) to linux 2.6, and I was wondering if there is
> a port of the IBM OCP GPIO driver (a char driver providing
> device /dev/gpio, major 10 minor 185). The driver was written by Armin
> Kuster, and it doesn't exist in the stock kernel 2.6.17.7.
> 
> Let me known if a port exists, or if there is a new way of accessing the
> PPC 405GP GPIO under linux 2.6.

The recommended way of accessing GPIO registers is to mmap them
and manipulate them directly in user space.

Below, I've included a quick hack that blinks a LED on a Walnut-like
board.

-Dale

#include <stdint.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

#define GPIO_PAGE_ADDR  0xef600000

#define OUTPUT_REG      0x0700
#define TRISTATE_REG    0x0704
#define OPENDRAIN_REG   0x0718
#define INPUT_REG       0x071c

#define MEDIA_LED_BIT   0x20000000

#define reg_addr(p, o)  ((uint32_t *)((void *)p + o))

int main(int argc, char *argv[])
{
        int i;
        uint32_t *p;
        char *filename = "/dev/mem";
        void *addr      = 0;
        size_t length   = 4096;
        int prot        = PROT_READ | PROT_WRITE;
        int flags       = MAP_SHARED;
        int fd          = open(filename, O_RDWR);
        off_t offset    = (off_t)GPIO_PAGE_ADDR;

        if (fd < 0) {
                perror("open");
                return 1;
        }

        p = mmap(addr, length, prot, flags, fd, offset);
        if (p == MAP_FAILED) {
                perror("mmap");
                return 4;
        }

        /* drive led output */
        *reg_addr(p, TRISTATE_REG) |= MEDIA_LED_BIT;

        /* blink media led 10 times */
        for (i = 0; i < 10; i++) {
                /* turn media led on */
                *reg_addr(p, OUTPUT_REG) &= ~MEDIA_LED_BIT;
                sleep(1);
                /* turn media led off */
                *reg_addr(p, OUTPUT_REG) |= MEDIA_LED_BIT;
                sleep(1);
        }

        return 0;
}