libbb: library for bit-banging the Ben's uSD port (in progress)

This doesn't work with old kernels, but 2.6.36 should be better. Haven't
tried it yet, though.

libbb/Makefile

@@ -0,0 +1,35 @@
+CC = mipsel-openwrt-linux-uclibc-gcc
+
+PREFIX = /usr/local
+
+LIBBD_PATH = $(PREFIX)/lib/libbbd
+
+CFLAGS = -Wall -DLIBBD_PATH='"$(LIBBD_PATH)"'
+
+MAIN = libbb.a libbbd
+
+.PHONY:		all install uninstall clean spotless upload
+
+all:		$(MAIN)
+
+libbb.a:	libbb.o
+		$(AR) cr $@ $^
+
+libbb.o libbd:	libbb.h
+
+install:	$(MAIN)
+		install -D libbb.a $(PREFIX)/lib/
+		install -D libbbd $(LIBBD_PATH)
+
+uninstall:
+		rm -f $(PREFIX)/lib/libbb.a
+		rm -f $(LIBBD_PATH)
+
+clean:
+		rm -f libbb.o
+
+spotless:	clean
+		rm -f $(MAIN)
+
+upload:		libbbd
+		scp libbbd ben:/usr/local/lib/

libbb/libbb.c

@@ -0,0 +1,126 @@
+/*
+ * 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);
+	}
+}

libbb/libbbd.c

@@ -0,0 +1,193 @@
+/*
+ * libbb/libbbd.c - Bitbang library daemon
+ *
+ * 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 <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);
+	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;
+}