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wernermisc/libbb/libbb.c

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/*
* libbb/libbb.c - Bitbang library
*
* Written 2010 by Werner Almesberger
* Copyright 2010 Werner Almesberger
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
//#include <sys/wait.h>
#include <sys/mman.h>
#include "libbb.h"
#define PAGE_SIZE 4096
volatile void *libbb_mem;
static int bbd_fd = -1;
static int recv_fd(int s)
{
struct msghdr msg;
struct cmsg {
struct cmsghdr hdr;
int fd;
} cmsg;
memset(&msg, 0, sizeof(msg));
msg.msg_control = &cmsg;
msg.msg_controllen = sizeof(cmsg);
if (recvmsg(s, &msg, 0) < 0) {
perror("recvmsg");
exit(1);
}
return cmsg.fd;
}
static void child(void)
{
execl(LIBBD_PATH, LIBBD_PATH, NULL);
perror(LIBBD_PATH);
_exit(1);
}
#if 0
static int recv_fd(int s)
{
pid_t res;
res = waitpid(pid, &status, 0);
if (res < 0) {
perror("waitpid");
exit(1);
}
if (res != pid) {
fprintf(stderr, "waitpid returned %d for %d\n",
(int) res, (int) pid);
exit(1);
}
}
#endif
static int bbd(void)
{
int s[2];
pid_t pid;
if (socketpair(PF_LOCAL, SOCK_DGRAM, 0, s) < 0) {
perror("socketpair");
exit(1);
}
if (dup2(s[1], 1) < 0) {
perror("dup2");
exit(1);
}
pid = fork();
if (pid < 0) {
perror("fork");
exit(1);
}
if (pid)
return recv_fd(s[0]);
else
child();
return -1; /* can't happen */
}
void libbb_open(void)
{
bbd_fd = bbd();
libbb_mem = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
bbd_fd, LIBBB_GPIO_BASE);
if (libbb_mem == MAP_FAILED) {
perror("mmap");
exit(1);
}
}
void libbb_close(void)
{
if (close(bbd_fd) < 0) {
perror("close");
exit(1);
}
}