seq_file学习(2)—— seq_file
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作者
平台
概述

正文
一、seq_demo驱动
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/slab.h>
static struct dentry *seq_demo_dir;
static LIST_HEAD(seq_demo_list);
static DEFINE_MUTEX(seq_demo_lock);
struct seq_demo_node {
char name[10];
struct list_head list;
};
static void *seq_demo_start(struct seq_file *s, loff_t *pos)
{
mutex_lock(&seq_demo_lock);
return seq_list_start(&seq_demo_list, *pos);
}
static void *seq_demo_next(struct seq_file *s, void *v, loff_t *pos)
{
return seq_list_next(v, &seq_demo_list, pos);
}
static void seq_demo_stop(struct seq_file *s, void *v)
{
mutex_unlock(&seq_demo_lock);
}
static int seq_demo_show(struct seq_file *s, void *v)
{
struct seq_demo_node *node = list_entry(v, struct seq_demo_node, list);
seq_printf(s, "name: %s, addr: 0x%p\n", node->name, node);
return 0;
}
static const struct seq_operations seq_demo_ops = {
.start = seq_demo_start,
.next = seq_demo_next,
.stop = seq_demo_stop,
.show = seq_demo_show,
};
static int seq_demo_open(struct inode *inode, struct file *file)
{
return seq_open(file, &seq_demo_ops);
}
static const struct file_operations seq_demo_fops = {
.owner = THIS_MODULE,
.open = seq_demo_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
static int __init seq_demo_init(void)
{
int i;
struct seq_demo_node *node;
for (i = 0; i < 7; i++) {
node = kzalloc(sizeof(struct seq_demo_node), GFP_KERNEL);
sprintf(node->name, "node%d", i);
INIT_LIST_HEAD(&node->list);
list_add_tail(&node->list, &seq_demo_list);
}
seq_demo_dir = debugfs_create_file("seq_demo", 0444, NULL,
NULL, &seq_demo_fops);
return 0;
}
static void __exit seq_demo_exit(void)
{
struct seq_demo_node *node_pos, *node_n;
if (seq_demo_dir) {
debugfs_remove(seq_demo_dir);
list_for_each_entry_safe(node_pos, node_n, &seq_demo_list, list)
if (node_pos) {
printk("%s: release %s\n", __func__, node_pos->name);
kfree(node_pos);
}
}
}
module_init(seq_demo_init);
module_exit(seq_demo_exit);
MODULE_LICENSE("GPL");
#include <linux/init.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/slab.h> static struct dentry *seq_demo_dir;
static LIST_HEAD(seq_demo_list);
static DEFINE_MUTEX(seq_demo_lock); struct seq_demo_node {
char name[];
struct list_head list;
}; static void *seq_demo_start(struct seq_file *s, loff_t *pos)
{
mutex_lock(&seq_demo_lock); return seq_list_start(&seq_demo_list, *pos);
} static void *seq_demo_next(struct seq_file *s, void *v, loff_t *pos)
{
return seq_list_next(v, &seq_demo_list, pos);
} static void seq_demo_stop(struct seq_file *s, void *v)
{
mutex_unlock(&seq_demo_lock);
} static int seq_demo_show(struct seq_file *s, void *v)
{
struct seq_demo_node *node = list_entry(v, struct seq_demo_node, list); seq_printf(s, "name: %s, addr: 0x%p\n", node->name, node); return ;
} static const struct seq_operations seq_demo_ops = {
.start = seq_demo_start,
.next = seq_demo_next,
.stop = seq_demo_stop,
.show = seq_demo_show,
}; static int seq_demo_open(struct inode *inode, struct file *file)
{
return seq_open(file, &seq_demo_ops);
} static const struct file_operations seq_demo_fops = {
.owner = THIS_MODULE,
.open = seq_demo_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
}; static int __init seq_demo_init(void)
{
int i;
struct seq_demo_node *node; for (i = ; i < ; i++) {
node = kzalloc(sizeof(struct seq_demo_node), GFP_KERNEL);
sprintf(node->name, "node%d", i); INIT_LIST_HEAD(&node->list);
list_add_tail(&node->list, &seq_demo_list);
} seq_demo_dir = debugfs_create_file("seq_demo", , NULL,
NULL, &seq_demo_fops);
return ;
} static void __exit seq_demo_exit(void)
{
struct seq_demo_node *node_pos, *node_n; if (seq_demo_dir) {
debugfs_remove(seq_demo_dir);
list_for_each_entry_safe(node_pos, node_n, &seq_demo_list, list)
if (node_pos) {
printk("%s: release %s\n", __func__, node_pos->name);
kfree(node_pos);
}
}
} module_init(seq_demo_init);
module_exit(seq_demo_exit);
MODULE_LICENSE("GPL");
下面是运行结果:
[root@vexpress mnt]# cat /d/seq_demo
name: node0, addr: 0xef252000
name: node1, addr: 0xef252680
name: node2, addr: 0xef252380
name: node3, addr: 0xef252740
name: node4, addr: 0xef252b00
name: node5, addr: 0xee80e480
name: node6, addr: 0xeeb9fd40
name: node7, addr: 0xeeb9fd00
二、分析
struct list_head *seq_list_start(struct list_head *head, loff_t pos)
{
struct list_head *lh; list_for_each(lh, head)
if (pos-- == )
return lh; return NULL;
}
struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
{
struct list_head *lh; lh = ((struct list_head *)v)->next;
++*ppos;
return lh == head ? NULL : lh;
}
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