[轉貼]使用/proc文件系統的一個簡單例子

[轉貼]使用/proc文件系統的一個簡單例子

kernel:2.6.28

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/jiffies.h>
#include <asm/uaccess.h>

#define MODULE_VERS "1.0"
#define MODULE_NAME "procfs_example"
#define FOOBAR_LEN    8

struct fb_data_t {
        char name[FOOBAR_LEN + 1];
        char value[FOOBAR_LEN + 1];
};
static struct proc_dir_entry *example_dir,*foo_file,\
                    *bar_file,*jiffies_file,*symlink; 
struct fb_data_t foo_data,bar_data;

//A read callback function for jiffies file
static int proc_read_jiffies(char *page,char **stat,\
            off_t off,int count,int *eof,void *data)
{
    int len;
      
    len = sprintf(page,"jiffies = %ld\n",jiffies); //jiffies is used as 
                            //the time counter of in the  Kernal
    return len;
}
//A read callback  function
static int proc_read_foobar (char *page,char **stat,\
                off_t off,int count,int *eof,void *data)
{
    int len;
    struct fb_data_t *fb_data = (struct fb_data_t *) data;
    len = sprintf(page,"%s = '%s'\n",fb_data->name,fb_data->value);
    return len;
}

//A write callback function for foobar_file
 static int proc_write_foobar (struct file *file,const char *buffer,\
             unsigned long count,void *data)
{
    int len;
    struct fb_data_t *fb_data = (struct fb_data_t *)data;
    if(count > FOOBAR_LEN)
      len = FOOBAR_LEN;
    else
      len = count;
    /*For buffer not exist in memory,so must copy it into Kernal first*/
    if(copy_from_user(fb_data->value,buffer,len))
      return -EFAULT;
    fb_data->value[len] = '\0';
    return len;
}

//init the MODULE
 static int __init init_procfs_example(void)
{
    int rv = 0;
    /*create directory*/
    example_dir = proc_mkdir(MODULE_NAME,NULL);
    /*handle the error*/
    if(example_dir == NULL){
        rv = -ENOMEM;
        goto out;
    }
    example_dir->owner = THIS_MODULE;
    /*create jiffies using convenience function*/
    jiffies_file = create_proc_read_entry("jiffies",0444,example_dir,\
                proc_read_jiffies,NULL);
    if(jiffies_file == NULL){
        rv = -ENOMEM;
        goto no_jiffies;
    }
    jiffies_file->owner = THIS_MODULE;
    /*creat foo and bar files using same callback functions*/
    foo_file = create_proc_entry("foo",0644,example_dir);
    if(foo_file == NULL){
        rv = -ENOMEM;
        goto no_foo;
    }
    strcpy(foo_data.name,"foo");
    strcpy(foo_data.value,"foo");
    foo_file->data = &foo_data;
    foo_file->read_proc = proc_read_foobar;
    foo_file->write_proc = proc_write_foobar;
    foo_file->owner = THIS_MODULE;

    bar_file = create_proc_entry("bar",0644,example_dir);
     if(bar_file == NULL){
          rv = -ENOMEM;
          goto no_bar;
    }
     strcpy(bar_data.name,"bar");
     strcpy(bar_data.value,"bar");
     bar_file->data = &bar_data;
     bar_file->read_proc = proc_read_foobar;
     bar_file->write_proc= proc_write_foobar;
     bar_file->owner = THIS_MODULE;

     /*create symlink*/
     symlink = proc_symlink("jiffies_too",example_dir,"jiffies");
     if(symlink == NULL){
         rv = -ENOMEM;
        goto no_symlink;
     }

     symlink->owner = THIS_MODULE;

     printk(KERN_INFO "%s %s initialised\n",MODULE_NAME,MODULE_VERS);
     return 0;

no_symlink:
     remove_proc_entry("symlink",example_dir);
no_bar:
     remove_proc_entry("bar",example_dir);
no_foo:
     remove_proc_entry("foo",example_dir);
no_jiffies:
     remove_proc_entry(MODULE_NAME,NULL);;
out:
     return rv;
}

static void __exit cleanup_procfs_example(void)
{
    remove_proc_entry("jiffies_too",example_dir);
    remove_proc_entry("bar",example_dir);
    remove_proc_entry("foo",example_dir);
    remove_proc_entry("jiffies",example_dir);
    remove_proc_entry(MODULE_NAME,NULL);

    printk(KERN_INFO "%s %s removed\n",MODULE_NAME,MODULE_VERS);

}
module_init(init_procfs_example);
module_exit(cleanup_procfs_example);

ref : 使用/proc文件系統的一個簡單例子