我正在为我们正在努力测试libudev的新平台创建测试应用程序，并确保在特定C时能够正确通知我们的usb应用程序插入或移除设备。
在我们的系统上，每次移除此设备并将其添加到其他位置（例如/dev/hidraw0或/dev/hidraw1等）时，我的测试应用程序会使用libudev来它们监视事件并通过hidraw设备进行枚举，以便它可以找到已安装的位置。每次设备状态更改，插入或删除时，代码都会找到它的安装位置并重新启动libudev事件监控。
我的问题：
1-我看到＆＃34;添加＆＃34;事件。但为什么我从未看到删除事件？
2-我是否正确关闭并重新启动libudev监控，以便资源不被泄露？
示例输出：
找到了UGA。 SYSPATH = [/ SYS /类/ hidraw / hidraw2] DevPath = [/ dev / hidraw2]
启动监视器返回2
UGA补充....发现UGA。 SYSPATH = [/ SYS /类/ hidraw / hidraw2] DevPath = [/ dev / hidraw2]
启动监视器返回2
UGA补充....发现UGA。 SysPath = [/ sys / class / hidraw / hidraw1] Dev Path = [/ dev / hidraw1]
启动监视器返回2
修改：
我所看到的是，这个测试应用程序在我们使用2.6内核的旧版x86平台上运行时接收remove事件，而在我们新的ARM平台上使用3.10.66内核运行的相同代码不会＃39;收到remove事件。
这可能是udev / libudev系统配置还是内核问题？
同样在ARM板上运行udevadm monitor时，正在发送所需的remove事件，如下所示。那么为什么没有libudev不将它们转发给我的应用程序呢？
box:/home/eng$ udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent
KERNEL[80296.266707] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001D (hid)
KERNEL[80296.266864] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
UDEV [80296.267553] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001D (hid)
KERNEL[80296.267695] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
UDEV [80296.268031] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
UDEV [80296.268890] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
KERNEL[80304.423516] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
KERNEL[80304.424514] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
KERNEL[80304.427211] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E (hid)
KERNEL[80304.458031] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E/hidraw/hidraw1 (hidraw)
UDEV [80304.460096] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
UDEV [80304.467105] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
UDEV [80304.472885] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E (hid)
UDEV [80304.474903] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E/hidraw/hidraw1 (hidraw)
测试代码：
/* Linux */
#include <linux/input.h>
#include <linux/hidraw.h>
#include <linux/fd.h>
/* Unix */
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <libudev.h>
#include <pthread.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
/* C */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <locale.h>
#include <stdbool.h>
#include <stdint.h>
#ifndef FALSE
#define FALSE 0
#define TRUE 1
#endif
struct udev *udev;
struct udev_monitor *udevMonitor;
int mon_fd = -1;
int fd = -1;
char sysPath[50];
char devPath[50];
enum { DEVICE_NO_CHANGE = 0, DEVICE_ADD, DEVICE_REMOVE, DEVICE_MOVED };
enum { OFFLINE = 0, ONLINE };
enum { ENABLED = 1, DISABLED };
enum { FAILED = 0, PENDING , ACTIVE };
void msSleep(int milliseconds);
void GetUGAMountPoints(void);
int StartUDEVMonitor(void);
int usb_check_device_status(void);
void GetUGAMountPoints(void)
{
struct udev_device *dev;
struct udev_enumerate *enumerate;
struct udev_list_entry *devices, *dev_list_entry;
strcpy( devPath, "/dev/hidraw" );
/* Create a list of the devices in the 'hidraw' subsystem. */
enumerate = udev_enumerate_new(udev);
udev_enumerate_add_match_subsystem(enumerate, "hidraw");
udev_enumerate_scan_devices(enumerate);
devices = udev_enumerate_get_list_entry(enumerate);
udev_list_entry_foreach(dev_list_entry, devices)
{
const char *path;
path = udev_list_entry_get_name(dev_list_entry);
dev = udev_device_new_from_syspath(udev, path);
dev = udev_device_get_parent_with_subsystem_devtype( dev, "usb", "usb_device");
if (!dev)
{
printf("Unable to find parent usb device.\n");
}
else
{
if( !strcmp(udev_device_get_sysattr_value(dev, "idVendor"), "0a70") &&
!strcmp(udev_device_get_sysattr_value(dev, "idProduct"), "0441") )
{
char num = path[ strlen(path) - 1 ];
devPath[ strlen(devPath) ] = num;
/* Yes I know this sprintf() is insecure and lazy
This code is just for testing and not going into
production in this form
*/
sprintf(sysPath, "/sys/class/hidraw/hidraw%c", num);
printf("Found UGA. SysPath=[%s] Dev Path=[%s]\n", sysPath, devPath);
udev_device_unref(dev);
break;
}
else
{
udev_device_unref(dev);
}
}
}
udev_enumerate_unref(enumerate);
return;
}
int StartUDEVMonitor(void)
{
int retCode = ACTIVE;
/* Create the udev object */
udev = udev_new();
if (!udev)
{
retCode = FAILED;
}
else
{
GetUGAMountPoints();
/* Set up a monitor to monitor hidraw devices */
udevMonitor = udev_monitor_new_from_netlink(udev, "kernel");
udev_monitor_filter_add_match_subsystem_devtype(udevMonitor, "hidraw", NULL);
udev_monitor_enable_receiving(udevMonitor);
mon_fd = udev_monitor_get_fd(udevMonitor);
fd = open(devPath, O_RDWR | O_NONBLOCK);
if (fd < 0)
{
retCode = PENDING;
}
}
return( retCode );
}
int usb_check_device_status(void)
{
struct udev_device *dev;
char action[25];
int retCode = DEVICE_NO_CHANGE;
fd_set fds;
struct timeval tv;
int ret;
FD_ZERO(&fds);
FD_SET(mon_fd, &fds);
tv.tv_sec = 0;
tv.tv_usec = 75000;
do
{
ret = select(mon_fd+1, &fds, NULL, NULL, &tv);
/* Check if our file descriptor has received data. */
if (ret > 0 && FD_ISSET(mon_fd, &fds))
{
FD_CLR(mon_fd, &fds);
/* Make the call to receive the device.
select() ensured that this will not block. */
dev = udev_monitor_receive_device(udevMonitor);
if (dev)
{
strcpy( action, udev_device_get_action(dev));
printf("usb_check_device_status()::[%s]\n", action);
if( !strcmp("remove",action))
{
printf("UGA removed....\n");
retCode = DEVICE_REMOVE;
}
else if( !strcmp("add",action))
{
printf("UGA added....\n");
retCode = DEVICE_ADD;
}
else if( !strcmp("move",action))
{
printf("UGA moved....\n");
retCode = DEVICE_MOVED;
}
udev_device_unref(dev);
}
}
}while( ret != 0 );
return( retCode );
}
void msSleep(int milliseconds)
{
usleep(milliseconds * 1000);
}
int main( int argc, char *argv[] )
{
int status = StartUDEVMonitor();
printf("Starting monitor returned %d\n",status);
if(status == ACTIVE )
{
while(1)
{
if( usb_check_device_status() != DEVICE_NO_CHANGE )
{
close(fd);
close(mon_fd);
udev_monitor_unref(udevMonitor);
udev_unref(udev);
StartUDEVMonitor();
printf("Starting monitor returned %d\n\n",status);
}
msSleep(75);
}
}
return( 1 );
}
答案 0 :(得分：1)
因此，通过查看udevadm monitor的输出，我能够看到在ARM板上的较新内核上，remove事件与hidraw不是tagged，因为它们与add事件如下所示：
box:/home/eng$ udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent
KERNEL[80296.266707] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001D (hid)
KERNEL[80296.266864] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
UDEV [80296.267553] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001D (hid)
KERNEL[80296.267695] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
UDEV [80296.268031] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
UDEV [80296.268890] remove /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
KERNEL[80304.423516] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
KERNEL[80304.424514] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
KERNEL[80304.427211] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E (hid)
KERNEL[80304.458031] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E/hidraw/hidraw1 (hidraw)
UDEV [80304.460096] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1 (usb)
UDEV [80304.467105] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0 (usb)
UDEV [80304.472885] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E (hid)
UDEV [80304.474903] add /devices/soc0/soc.1/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.0/0003:0A70:0441.001E/hidraw/hidraw1 (hidraw)
通过更改StartUDEVMonitor()中的过滤器设置：
udev_monitor_filter_add_match_subsystem_devtype(udevMonitor, "hidraw", NULL);
于：
udev_monitor_filter_add_match_subsystem_devtype(udevMonitor, "hid", NULL);
现在，应用程序可以使用较新的内核在较新的平台上可靠地接收remove和add个事件。