usb.c

来自「The source code example of ARM9 developm」· C语言 代码 · 共 87 行

/*
 *	Description: 
 *		example for usb.
 *	
 *		What is shown in this example:
 *		1. How to mount usb device
 *		2. How to write a file to usb device
 *		3. How to umount usb device
 */
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/mount.h>
#include <unistd.h>

const char buf[] = "MATRIX USB Example\n";

int main(void)
{
	int	ret, usb_type, fd;
	char	filename[128], target[128];

	/*mount USB device*/
	ret = mount("/dev/sda", "/mnt/sda", "vfat", MS_SYNCHRONOUS, NULL);
	if (ret == -1) {
		if (errno == EROFS) {
			printf("/dev/sda is write-protected\r\n");
			return;
		}
		/*if /dev/sda not found, try /dev/sda1*/
		ret = mount("/dev/sda1", "/mnt/sda1", "vfat", MS_SYNCHRONOUS, NULL);
		if (ret == -1) {
			if (errno == EROFS) {
				printf("/dev/sda is write-protected\r\n");
			} else {
				printf("no device found\r\n");
			}
			return;
		} else {
			printf("found /dev/sda1\r\n");
			usb_type = 1;
		}
	} else {
		printf("found /dev/sda\r\n");
		usb_type = 0;
	}

	if (usb_type == 0) {
		sprintf(filename, "/mnt/sda/tmpfile");
	} else {
		sprintf(filename, "/mnt/sda1/tmpfile");
	}
	
	/*create file on USB device*/
	fd = open(filename, O_CREAT|O_WRONLY|O_TRUNC);
	if (fd == -1) {
		printf("create file failed. errno: %d\r\n", errno);		
	} else {
		/*write file to USB device*/
		ret = write(fd, buf, sizeof(buf));
		if (ret == -1) {
			printf("write file failed. errno: %d\r\n", errno);
		} else {
			printf("write tmpfile to USB device ok\r\n");
		}
	}
	close(fd);

	if (usb_type == 0) {
		sprintf(target, "/mnt/sda");
	} else {
		sprintf(target, "/mnt/sda1");
	}
	/*umount USB device*/
	while (1) {
		ret = umount(target);
		if (ret != 0) {
			if (errno == EBUSY) { 
				sleep(1);
				continue;
			}	
		}
		printf("umount %s\r\n", target);
		break;
	}
}