据我所知,为了从内核空间通知用户空间,一种方法是使用poll。这意味着内核驱动程序应该首先提供poll方法。
下面的代码来自于互联网,它确实可行!
我可以这样做使它工作:
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Fortune Cookie Kernel Module");
MODULE_AUTHOR("M. Tim Jones");
#define MAX_COOKIE_LENGTH PAGE_SIZE
static struct proc_dir_entry *proc_entry;
static char *cookie_buf; // Space for fortune strings
static int write_index; // Index to write next fortune
static int read_index; // Index to read next fortune
ssize_t fortune_write( struct file *filp, const char __user *buff,
unsigned long len, void *data )
// Refer to: ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
{
int space_available = (MAX_COOKIE_LENGTH-write_index);
if (len > space_available) {
printk(KERN_INFO "fortune: cookie buffer is full!\n");
return -ENOSPC;
}
if (copy_from_user( &cookie_buf[write_index], buff, len )) {
return -EFAULT;
}
write_index += len;
cookie_buf[write_index-1] = 0;
return len;
}
ssize_t fortune_read(struct file *file, char *buf, size_t count, loff_t *f_pos){
// Refer to: ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
int len;
//there's no fortune or a fortune has already been read
//the *f_pos > 0 hack is needed because `cat /proc/fortune` would otherwise
//display every thing in the cookie_buf
if(write_index == 0 || *f_pos > 0){
return 0;
}
// cicle through fortunes
if(read_index >= write_index){
read_index = 0;
}
len = sprintf(buf, "%s\n", &cookie_buf[read_index]);
read_index += len;
*f_pos += len;
return len;
}
static const struct file_operations proc_test_fops = {
.owner = THIS_MODULE,
// .open = led_proc_open,
.read = fortune_read,
// .llseek = seq_lseek,
// .release = single_release,
.write = fortune_write,
// unsigned int (*poll) (struct file *, struct poll_table_struct *);
// int (*fasync) (int, struct file *, int);
};
int __init init_fortune_module( void )
{
int ret = 0;
cookie_buf = (char *)vmalloc( MAX_COOKIE_LENGTH );
if (!cookie_buf) {
ret = -ENOMEM;
} else {
memset( cookie_buf, 0, MAX_COOKIE_LENGTH );
// proc_entry = create_proc_entry( "fortune", 0644, NULL );
proc_entry = proc_create( "fortune", 0644, NULL, &proc_test_fops );
if (proc_entry == NULL) {
ret = -ENOMEM;
vfree(cookie_buf);
printk(KERN_INFO "fortune: Couldn't create proc entry\n");
} else {
write_index = 0;
read_index = 0;
printk(KERN_INFO "fortune: Module loaded.\n");
}
}
return ret;
}
void __exit exit_fortune_module( void )
{
// remove_proc_entry("fortune", &proc_entry);
proc_remove(proc_entry);
vfree(cookie_buf);
printk(KERN_INFO "fortune: Module unloaded.\n");
}
module_init( init_fortune_module );
module_exit( exit_fortune_module );
我可以这样做使它工作:
echo "hello" > /proc/fortune
然后
cat /proc/fortune
想要查看结果。但如何添加投票方法呢?我尝试了几次,但仍然失败。
hw3_poll()
中,poll_wait()
会睡眠并等待被唤醒,然后检查data_ready
以确保我们被唤醒是因为实际上有新数据可供读取。而在hw3_btn_isr()
(中断处理程序)中,data_ready
被设置为true
,然后调用wake_up_interruptible()
来唤醒等待队列。 - Sam Protsenko