做的好的网站开发,安装wordpress程序,网站的服务器选择,五八同城找工作招聘信息基础知识 poll和select方法在Linux用户空间的API接口函数定义如下。 int poll(struct pollfd *fds, nfds_t nfds, int timeout); poll()函数的第一个参数fds是要监听的文件描述符集合#xff0c;类型为指向struct pollfd的指针。struct pollfd数据结构定义如下。 struct poll…基础知识 poll和select方法在Linux用户空间的API接口函数定义如下。 int poll(struct pollfd *fds, nfds_t nfds, int timeout); poll()函数的第一个参数fds是要监听的文件描述符集合类型为指向struct pollfd的指针。struct pollfd数据结构定义如下。 struct pollfd {int fd;short events;short revents;
}; fd表示要监听的文件描述符events表示监听的事件revents表示返回的事件。常用的监听的事件有如下类型掩码。 POLLIN数据可以立即被读取。 POLLRDNORM等同于POLLIN表示数据可以立即被读取。 POLLERR设备发生了错误。 POLLOUT设备可以立即写入数据。 poll()函数的第二个参数nfds是要监听的文件描述符的个数第三个参数timeout是单位为ms的超时负数表示一直监听直到被监听的文件描述符集合中有设备发生了事件。 Linux内核的file_operations方法集提供了poll方法的实现。 include/linux/fs.h
struct file_operations {…unsigned int (*poll) (struct file *, struct poll_table_struct *);…
}; 当用户程序打开设备文件后执行poll或者select系统调用时驱动程序的poll方法就会被调用。设备驱动程序的poll方法会执行如下步骤。 1在一个或者多个等待队列中调用poll_wait()函数。poll_wait()函数会把当前进程添加到指定的等待列表poll_table中当请求数据准备好之后会唤醒这些睡眠的进程。 2返回监听事件也就是POLLIN或者POLLOUT等掩码。因此poll方法的作用就是让应用程序同时等待多个数据流。 驱动代码
#include linux/module.h
#include linux/init.h
#include linux/fs.h
#include linux/cdev.h
#include linux/device.h
#include linux/slab.h
#include linux/uaccess.h
#include linux/types.h
#include linux/miscdevice.h
#include linux/kfifo.h
#include linux/wait.h
#include linux/poll.h#define DEBUG_INFO(format, ...) printk(%s:%d -- format\n,\
__func__,__LINE__,##__VA_ARGS__)struct ch5_kfifo_struct{struct miscdevice misc;struct file_operations fops;struct kfifo fifo;char buf[64];char name[64];wait_queue_head_t read_queue;wait_queue_head_t write_queue;
};static int ch5_open (struct inode *inode, struct file *file){struct ch5_kfifo_struct *p (struct ch5_kfifo_struct *)container_of(file-f_op,struct ch5_kfifo_struct,fops);file-private_data p;DEBUG_INFO(major %d, minor %d\n,MAJOR(inode-i_rdev),MINOR(inode-i_rdev));DEBUG_INFO(name %s,p-misc.name);return 0;
}static int ch5_release (struct inode *inode, struct file *file){DEBUG_INFO(close);return 0;
}static unsigned int ch5_poll(struct file *file, poll_table *wait){int mask 0;struct ch5_kfifo_struct *p __attribute__((unused)) (struct ch5_kfifo_struct *)file-private_data;DEBUG_INFO(begin wait:%s,p-name);poll_wait(file, p-read_queue, wait);poll_wait(file, p-write_queue, wait);DEBUG_INFO(poll:%s,p-name);if (!kfifo_is_empty(p-fifo)){mask | POLLIN | POLLRDNORM;DEBUG_INFO(POLLIN:%s,p-name);}if (!kfifo_is_full(p-fifo)){mask | POLLOUT | POLLWRNORM;DEBUG_INFO(POLLOUT:%s,p-name);}return mask;
}static ssize_t ch5_read (struct file *file, char __user *buf, size_t size, loff_t *pos){struct ch5_kfifo_struct *p __attribute__((unused)) (struct ch5_kfifo_struct *)file-private_data;int ret;int actual_readed 0;if(kfifo_is_empty(p-fifo)){if(file-f_flags O_NONBLOCK){DEBUG_INFO(kfifo is null);return -EAGAIN;}ret wait_event_interruptible(p-read_queue,kfifo_is_empty(p-fifo) 0);if(ret){DEBUG_INFO(wait_event_interruptible error);return ret;}DEBUG_INFO();}ret kfifo_to_user(p-fifo, buf, size, actual_readed);if (ret){DEBUG_INFO(kfifo_to_user error);return -EIO;}DEBUG_INFO(size %d,actual_readed %d\n,size,actual_readed);if (!kfifo_is_full(p-fifo)){wake_up_interruptible(p-write_queue);}memset(p-buf,0,sizeof(p-buf));ret copy_from_user(p-buf, buf, actual_readed);if(ret ! 0){DEBUG_INFO(copy_from_user error ret %d\n,ret);}else{DEBUG_INFO(read p-buf %s\n,p-buf);}*pos *pos actual_readed;return actual_readed;
}
static ssize_t ch5_write (struct file *file, const char __user *buf, size_t size, loff_t* pos){struct ch5_kfifo_struct *p (struct ch5_kfifo_struct *)file-private_data;int actual_writed 0;int ret;if(kfifo_is_full(p-fifo)){if(file-f_flags O_NONBLOCK){DEBUG_INFO(kfifo is full);return -EAGAIN;}ret wait_event_interruptible(p-write_queue, kfifo_is_full(p-fifo) 0);if(ret){DEBUG_INFO(wait_event_interruptible error);return ret;}DEBUG_INFO();}ret kfifo_from_user(p-fifo, buf, size, actual_writed);if (ret){DEBUG_INFO(kfifo_from_user error);return -EIO;}DEBUG_INFO(actual_writed %d\n,actual_writed);if (!kfifo_is_empty(p-fifo)){wake_up_interruptible(p-read_queue);}memset(p-buf,0,sizeof(p-buf));ret copy_from_user(p-buf, buf, actual_writed);if(ret ! 0){DEBUG_INFO(copy_from_user error ret %d\n,ret);}else{DEBUG_INFO(write:p-buf %s\n,p-buf);}*pos *pos actual_writed;return actual_writed;
}struct ch5_kfifo_struct ch5_kfifo[8];
// {
// .misc {
// .name ch5-04-block,
// .minor MISC_DYNAMIC_MINOR,
// },
// .fops {
// .owner THIS_MODULE,
// .read ch5_read,
// .write ch5_write,
// .open ch5_open,
// .release ch5_release,
// },
// };static int __init ch5_init(void){int ret 0;int i 0;struct ch5_kfifo_struct *p;DEBUG_INFO(start init\n);for(i 0;i sizeof(ch5_kfifo)/sizeof(ch5_kfifo[0]);i){p ch5_kfifo[i];snprintf(p-name,sizeof(p-name),ch5-05-poll-%d,i);p-misc.name p-name;p-misc.minor MISC_DYNAMIC_MINOR;p-fops.owner THIS_MODULE;p-fops.read ch5_read;p-fops.write ch5_write;p-fops.open ch5_open;p-fops.release ch5_release;p-fops.poll ch5_poll;p-misc.fops p-fops;ret kfifo_alloc(p-fifo,8,GFP_KERNEL);if (ret) {DEBUG_INFO(kfifo_alloc error: %d\n, ret);ret -ENOMEM;return ret;}DEBUG_INFO(kfifo_alloc size %d,kfifo_avail(p-fifo));init_waitqueue_head(p-read_queue);init_waitqueue_head(p-write_queue);ret misc_register(p-misc);if(ret 0){DEBUG_INFO(misc_register error: %d\n, ret);return ret;}}DEBUG_INFO(misc_register ok);return 0;
}static void __exit ch5_exit(void){int i 0;struct ch5_kfifo_struct *p;for(i 0;i sizeof(ch5_kfifo)/sizeof(ch5_kfifo[0]);i){p ch5_kfifo[i];misc_deregister(p-misc);kfifo_free(p-fifo);}DEBUG_INFO(exit\n);
}module_init(ch5_init);
module_exit(ch5_exit);MODULE_LICENSE(GPL);
应用测试代码
#include stdio.h
#include stdlib.h
#include string.h
#include sys/types.h
#include sys/stat.h
#include sys/ioctl.h
#include fcntl.h
#include errno.h
#include poll.h
#include linux/input.h
#include unistd.h#define DEBUG_INFO(format, ...) printf(%s:%d -- format\n,\
__func__,__LINE__,##__VA_ARGS__)int main(int argc, char**argv){char bufs[8][1024];char name[8][1024];int fd[8];int i 0;int ret;int len;struct pollfd fds[8];for(i 0;i 8;i){memset(name[i], 0, sizeof(name[i]));snprintf(name[i], sizeof(name[i]),/dev/ch5-05-poll-%d,i);fd[i] open(name[i],O_RDONLY | O_NONBLOCK);if(fd[i] 0){perror(open);DEBUG_INFO(open %s failed,name[i]);return -1;}fds[i].fd fd[i];fds[i].events POLLIN;fds[i].revents 0;}DEBUG_INFO(start poll\n);while(1){ret poll(fds,8,-1);if(ret 0){perror(poll);return 0;}DEBUG_INFO(ret %d\n,ret);for(i 0;i 8;i){if(fds[i].revents POLLIN){while(1){memset(bufs[i],0,sizeof(bufs[i]));len read(fd[i],(void*)bufs[i][0],sizeof(bufs[i]));if(len 0){DEBUG_INFO(read %s finish,name[i]);break;}DEBUG_INFO(read %s :buf %s,name[i],bufs[i]);}}}}return 0;
}
测试
加载模块生成8个设备 后台运行应用
/mnt # ./app
/mnt # [ 519.185812] ch5_open:30 -- major 10, minor 58
[ 519.185812]
[ 519.186175] ch5_open:31 -- name ch5-05-poll-0
[ 519.186849] ch5_open:30 -- major 10, minor 57
[ 519.186849]
[ 519.187772] ch5_open:31 -- name ch5-05-poll-1
[ 519.190276] ch5_open:30 -- major 10, minor 56
[ 519.190276]
[ 519.190553] ch5_open:31 -- name ch5-05-poll-2
[ 519.191129] ch5_open:30 -- major 10, minor 55
[ 519.191129]
[ 519.191604] ch5_open:31 -- name ch5-05-poll-3
[ 519.192090] ch5_open:30 -- major 10, minor 54
[ 519.192090]
[ 519.192283] ch5_open:31 -- name ch5-05-poll-4
[ 519.192759] ch5_open:30 -- major 10, minor 53
[ 519.192759]
[ 519.193020] ch5_open:31 -- name ch5-05-poll-5
[ 519.193486] ch5_open:30 -- major 10, minor 52
[ 519.193486]
[ 519.193677] ch5_open:31 -- name ch5-05-poll-6
[ 519.194148] ch5_open:30 -- major 10, minor 51
[ 519.194148]
[ 519.194340] ch5_open:31 -- name ch5-05-poll-7
main:38 -- start poll[ 519.199679] ch5_poll:43 -- begin wait:ch5-05-poll-0
[ 519.200029] ch5_poll:46 -- poll:ch5-05-poll-0
[ 519.200236] ch5_poll:54 -- POLLOUT:ch5-05-poll-0
[ 519.200358] ch5_poll:43 -- begin wait:ch5-05-poll-1
[ 519.200598] ch5_poll:46 -- poll:ch5-05-poll-1
[ 519.200770] ch5_poll:54 -- POLLOUT:ch5-05-poll-1
[ 519.201213] ch5_poll:43 -- begin wait:ch5-05-poll-2
[ 519.201531] ch5_poll:46 -- poll:ch5-05-poll-2
[ 519.201646] ch5_poll:54 -- POLLOUT:ch5-05-poll-2
[ 519.201727] ch5_poll:43 -- begin wait:ch5-05-poll-3
[ 519.201847] ch5_poll:46 -- poll:ch5-05-poll-3
[ 519.201998] ch5_poll:54 -- POLLOUT:ch5-05-poll-3
[ 519.202154] ch5_poll:43 -- begin wait:ch5-05-poll-4
[ 519.202347] ch5_poll:46 -- poll:ch5-05-poll-4
[ 519.202504] ch5_poll:54 -- POLLOUT:ch5-05-poll-4
[ 519.202661] ch5_poll:43 -- begin wait:ch5-05-poll-5
[ 519.202850] ch5_poll:46 -- poll:ch5-05-poll-5
[ 519.203122] ch5_poll:54 -- POLLOUT:ch5-05-poll-5
[ 519.203276] ch5_poll:43 -- begin wait:ch5-05-poll-6
[ 519.203490] ch5_poll:46 -- poll:ch5-05-poll-6
[ 519.203643] ch5_poll:54 -- POLLOUT:ch5-05-poll-6
[ 519.203798] ch5_poll:43 -- begin wait:ch5-05-poll-7
[ 519.203964] ch5_poll:46 -- poll:ch5-05-poll-7
[ 519.204109] ch5_poll:54 -- POLLOUT:ch5-05-poll-7写数据
/mnt # echo hello world /dev/ch5-05-poll-0
[ 576.205375] ch5_open:30 -- major 10, minor 58
[ 576.205375]
[ 576.206863] ch5_open:31 -- name ch5-05-poll-0
[ 576.208285] ch5_write:122 -- actual_writed 8
[ 576.208285]
[ 576.208757] ch5_write:132 -- write:p-buf hello wo
[ 576.208757]
[ 576.209448] ch5_poll:43 -- begin wait:ch5-05-poll-0
[ 576.209675] ch5_poll:46 -- poll:ch5-05-poll-0
[ 576.209874] ch5_poll:49 -- POLLIN:ch5-05-poll-0
[ 576.210058] ch5_poll:43 -- begin wait:ch5-05-poll-1
[ 576.210291] ch5_poll:46 -- poll:ch5-05-poll-1
[ 576.210451] ch5_poll:54 -- POLLOUT:ch5-05-poll-1
[ 576.210645] ch5_poll:43 -- begin wait:ch5-05-poll-2
[ 576.211496] ch5_poll:46 -- poll:ch5-05-poll-2
[ 576.212140] ch5_poll:54 -- POLLOUT:ch5-05-poll-2
[ 576.212315] ch5_poll:43 -- begin wait:ch5-05-poll-3
[ 576.212517] ch5_poll:46 -- poll:ch5-05-poll-3
[ 576.212707] ch5_poll:54 -- POLLOUT:ch5-05-poll-3
[ 576.212928] ch5_poll:43 -- begin wait:ch5-05-poll-4
[ 576.213169] ch5_poll:46 -- poll:ch5-05-poll-4
[ 576.213333] ch5_poll:54 -- POLLOUT:ch5-05-poll-4
[ 576.213515] ch5_poll:43 -- begin wait:ch5-05-poll-5
[ 576.213752] ch5_poll:46 -- poll:ch5-05-poll-5
[ 576.213869] ch5_poll:54 -- POLLOUT:ch5-05-poll-5
[ 576.214067] ch5_poll:43 -- begin wait:ch5-05-poll-6
[ 576.214238] ch5_poll:46 -- poll:ch5-05-poll-6
[ 576.214392] ch5_poll:54 -- POLLOUT:ch5-05-poll-6
[ 576.214545] ch5_poll:43 -- begin wait:ch5-05-poll-7
[ 576.214963] ch5_poll:46 -- poll:ch5-05-poll-7
[ 576.215300] ch5_poll:54 -- POLLOUT:ch5-05-poll-7
main:45 -- ret 1
[ 576.216522] ch5_read:84 -- size 1024,actual_readed 8
[ 576.216522]
[ 576.216920] ch5_read:95 -- read p-buf hello wo
[ 576.216920]
[ 576.217219] ch5_write:114 --
main:55 -- read /dev/ch5-05-poll-0 :buf hello wo
[ 576.217652] ch5_write:122 -- actual_writed 4
[ 576.217652]
[ 576.217989] ch5_write:132 -- write:p-buf rld
[ 576.217989]
[ 576.217989]
main:55 -- read /dev/ch5-05-poll-0 :buf rld[ 576.218140] ch5_read:84 -- size 1024,actual_readed 4
[ 576.218140] [ 576.218294] ch5_read:95 -- read p-buf rld
[ 576.218294]
[ 576.218294] [ 576.219434] ch5_read:67 -- kfifo is null
main:52 -- read /dev/ch5-05-poll-0 finish[ 576.220169] ch5_release:36 -- close[ 576.220874] ch5_poll:43 -- begin wait:ch5-05-poll-0
[ 576.221959] ch5_poll:46 -- poll:ch5-05-poll-0
[ 576.222639] ch5_poll:54 -- POLLOUT:ch5-05-poll-0
[ 576.224333] ch5_poll:43 -- begin wait:ch5-05-poll-1
[ 576.225068] ch5_poll:46 -- poll:ch5-05-poll-1
[ 576.225443] ch5_poll:54 -- POLLOUT:ch5-05-poll-1
[ 576.225890] ch5_poll:43 -- begin wait:ch5-05-poll-2
[ 576.226298] ch5_poll:46 -- poll:ch5-05-poll-2
[ 576.226829] ch5_poll:54 -- POLLOUT:ch5-05-poll-2
[ 576.227435] ch5_poll:43 -- begin wait:ch5-05-poll-3
/mnt # [ 576.227639] ch5_poll:46 -- poll:ch5-05-poll-3
[ 576.227892] ch5_poll:54 -- POLLOUT:ch5-05-poll-3
[ 576.228124] ch5_poll:43 -- begin wait:ch5-05-poll-4
[ 576.228344] ch5_poll:46 -- poll:ch5-05-poll-4
[ 576.228573] ch5_poll:54 -- POLLOUT:ch5-05-poll-4
[ 576.228902] ch5_poll:43 -- begin wait:ch5-05-poll-5
[ 576.229155] ch5_poll:46 -- poll:ch5-05-poll-5
[ 576.229349] ch5_poll:54 -- POLLOUT:ch5-05-poll-5
[ 576.229573] ch5_poll:43 -- begin wait:ch5-05-poll-6
[ 576.229761] ch5_poll:46 -- poll:ch5-05-poll-6
[ 576.230005] ch5_poll:54 -- POLLOUT:ch5-05-poll-6
[ 576.230233] ch5_poll:43 -- begin wait:ch5-05-poll-7
[ 576.230421] ch5_poll:46 -- poll:ch5-05-poll-7
[ 576.231095] ch5_poll:54 -- POLLOUT:ch5-05-poll-7小结
