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