在Android的Vold里面可以了解到，其检测USB的插拔是通过Netlink机制来实现的，那我们也来尝试下如何在Linux下写个程序检测USB设备的插拔，下面我们将使用Netlink的NETLINK_KOBJECT_UEVENT类型套接字与Kernel进行通信，然后使用setsocketopt()来利用该套接字，再使用select()并发检测相应的套接写是否可操作，具体的代码实现 如下：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#define UEVENT_BUFFER_SIZE 2048
int main(void)
{
struct sockaddr_nl client;
struct timeval tv;
int fd, rcvlen, ret;
fd_set fds;
int buffersize = 1024;
fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_KOBJECT_UEVENT);
memset(&client, 0, sizeof(client));
client.nl_family = AF_NETLINK;
client.nl_pid = getpid();
client.nl_groups = 1; /* receive broadcast message*/
setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &buffersize, sizeof(buffersize));
bind(fd, (struct sockaddr*)&client, sizeof(client));
while (1) {
char buf[UEVENT_BUFFER_SIZE] = { 0 };
FD_ZERO(&fds);
FD_SET(fd, &fds);
tv.tv_sec = 0;
tv.tv_usec = 100 * 1000;
ret = select(fd + 1, &fds, NULL, NULL, &tv);
if(ret < 0)
continue;
if(!(ret > 0 && FD_ISSET(fd, &fds)))
continue;
/* receive data */
rcvlen = recv(fd, &buf, sizeof(buf), 0);
if (rcvlen > 0) {
printf("%s\n", buf);
/*You can do something here to make the program more perfect!!!*/
}
}
close(fd);
return 0;
}
然后将其交叉编译下并放到我们的Mstar板卡上，插拔U盘和USB鼠标时有如下提示：
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2
add@/devices/platform/Mstar[ 120.529879] scsi0 : usb-storage 4-1.2:1.0-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0
add@/devices[ 120.537275] isa bounce pool size: 16 pages/platform/Mstar-[ 120.543612] scsi 0:0:0:0: Direct-Access SanDisk Cruzer Blade 2.01 PQ: 0 ANSI: 5
ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0
add@/de[ 120.556037] sd 0:0:0:0: [sda] 7821312 512-byte logical blocks: (4.00 GB/3.72 GiB)
vices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1[ 120.567115] sd 0:0:0:0: [sda] Write Protect is off
.2:1.0/host0/scs[ 120.573404] sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
i_host/host0
add@/devices/platform/Mstar-ehci-2[ 120.587278] emmc_partition()
.1/usb4/4-1/4-1.2/usb_device/usbdev4.4
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.[ 120.598422] 0x0
2:1.0/host0/targ[ 120.600753] sda: sda1
et0:0:0
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0/scsi_disk/0:0:0:0
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0/scsi_device[ 120.629463] sd 0:0:0:0: [sda]
Attached SCSI removable disk
/0:0:0:0
add@/devices/virtual/bdi/8:0
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0/block/sda
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0/block/sda/sda1
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-[ 163.282004] input: PIXART USB OPTICAL MOUSE as /devices/platform/Mstar-ehci
2.1/usb4/4-1/4-1.4/4-1.4:1.0/input/input10
1.4/4-1.4:1.0
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1[ 163.297335] generic-usb 0003:093A:2510.0003: input,hidraw1: USB HID v1.11 Mouse
[PIXART USB OPTICAL MOUSE] on usb-mstar-1.4/input0
.4/4-1.4:1.0/0003:093A:2510.0003
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/input/input10
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/input/input10/mouse2
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/input/input10/event4
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/0003:093A:2510.0003/hidraw/hidraw1
add@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/usb_device/usbdev4.5
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0/block/sda/sda1
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0/scsi_disk/0:0:0:0
remove@/devices/virtual/bdi/8:0
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0/block/sda
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0/0:0:0:0
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/target0:0:0
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0/scsi_host/host0
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0/host0
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/4-1.2:1.0
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2/usb_device/usbdev4.4
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.2
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/input/input4/mouse2
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/input/input4/event4
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/input/input4
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/0003:093A:2510.0002/hidraw/hidraw1
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0/0003:093A:2510.0002
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/4-1.4:1.0
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4/usb_device/usbdev4.3
remove@/devices/platform/Mstar-ehci-2.1/usb4/4-1/4-1.4
从上面的打印信息，我们看到插入时会以add@开头，而拔掉时会以remove@开头，通过判断这样的头部信息可以判断是不是有设备进行插拔，进而再处理后面的内容来判断具体是哪个设备。
参考网址：
http://www.cpplive.com/html/1355.html
http://www.linuxidc.com/Linux/2012-02/53354.htm
http://www.linuxidc.com/Linux/2011-12/49112.htm
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