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wernermisc/libbb/libbbd.c

194 lines
3.5 KiB
C

/*
* libbb/libbbd.c - Bitbang library daemon
*
* Written 2010-2011 by Werner Almesberger
* Copyright 2010-2011 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 <fcntl.h>
#include <dirent.h>
#include <poll.h>
#include <errno.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/socket.h>
#include "libbb.h"
#define FD_DIR "/proc/self/fd"
#define DRIVER_NAME "jz4740-mmc.0"
#define UNBIND_PATH "/sys/bus/platform/drivers/jz4740-mmc/unbind"
#define BIND_PATH "/sys/bus/platform/drivers/jz4740-mmc/bind"
static void closefds(void)
{
DIR *dir;
const struct dirent *de;
int fd;
dir = opendir(FD_DIR);
if (!dir) {
perror(FD_DIR);
exit(1);
}
while ((de = readdir(dir))) {
if (*de->d_name == '.')
continue;
fd = atoi(de->d_name);
if (fd == 1 || fd == 2)
continue;
if (fd == dirfd(dir))
continue;
(void) close(fd);
}
closedir(dir);
}
static int echo(const char *msg, const char *path)
{
int fd;
ssize_t wrote;
int len = strlen(msg);
fd = open(path, O_WRONLY);
if (fd < 0) {
perror(path);
return -errno;
}
wrote = write(fd, msg, len);
if (wrote < 0) {
perror(path);
return -errno;
}
if (wrote != len) {
fprintf(stderr, "short write: %d < %d\n", (int) wrote, len);
return -ENOSPC;
}
if (close(fd) < 0) {
perror(path);
return -errno;
}
return 0;
}
static void lock_area(int fd, off_t from, off_t len)
{
if (lseek(fd, from, SEEK_SET) == (off_t) -1) {
perror("lseek");
exit(1);
}
if (lockf(fd, F_LOCK, len) < 0) {
perror("lockf");
exit(1);
}
}
static int send_fd(int s, int fd)
{
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);
cmsg.hdr.cmsg_level = SOL_SOCKET;
cmsg.hdr.cmsg_type = SCM_RIGHTS;
cmsg.hdr.cmsg_len = sizeof(cmsg);
cmsg.fd = fd;
if (sendmsg(s, &msg, 0) >= 0)
return 0;
perror("sendmsg");
return -1;
}
static int wait_for_close(int s)
{
struct pollfd fds[1];
int res;
fds->fd = s;
fds->events = 0;
fds->revents = POLLHUP;
res = poll(fds, 1, -1);
if (res < 0) {
perror("poll");
return -1;
}
if (!res) {
fprintf(stderr, "poll inexplicably returned 0\n");
return -1;
}
return 0;
}
int main(int argc, char **argv)
{
int fd, res;
int exit_code = 1;
fprintf(stderr, "setsid\n");
if (setsid() == (pid_t) -1) {
perror("setsid");
exit(1);
}
fprintf(stderr, "closefds\n");
closefds();
fprintf(stderr, "open devmem\n");
fd = open("/dev/mem", O_RDWR | O_SYNC);
if (fd < 0) {
perror("/dev/mem");
exit(1);
}
fprintf(stderr, "lock_area\n");
lock_area(fd, LIBBB_GPIO_BASE+LIBBB_PORT_D_OFFSET,
LIBBB_PORT_D_WINDOW);
fprintf(stderr, "echo (unbind)\n");
if (echo(DRIVER_NAME "\n", UNBIND_PATH) < 0)
exit(1);
fprintf(stderr, "send_fd\n");
if (send_fd(1, fd) < 0)
goto cleanup;
fprintf(stderr, "wait_for_close\n");
if (wait_for_close(1) < 0)
goto cleanup;
exit_code = 0;
cleanup:
fprintf(stderr, "echo (bind)n");
res = echo(DRIVER_NAME "\n", BIND_PATH);
if (res < 0) {
/* stderr may no longer exist. report to syslog. */
openlog("libbbd", LOG_CONS, LOG_USER);
syslog(LOG_CRIT, "libbd failed to re-bind driver (%d)", res);
}
fprintf(stderr, "exit\n");
return exit_code;
}