Email: BuddyZhang1 buddy.zhang@aliyun.com
目录
源码分析
#ifdef CONFIG_DEBUG_LIST
extern bool __list_add_valid(struct list_head *new,
struct list_head *prev,
struct list_head *next);
#else
static inline bool __list_add_valid(struct list_head *new,
struct list_head *prev,
sst_add_validtruct list_head *next)
{
return true;
}
#endif__list_add_valid() 函数用于添加一个节点的时候，检查新加的节点是否可用。其定义 与 CONFIG_DEBUG_LIST 宏有关。如果 CONFIG_DEBUG_LIST 宏开启，那么 __list_add_valid() 的实现如下：
bool __list_add_valid(struct list_head *new, struct list_head *prev,
struct list_head *next)
{
if (CHECK_DATA_CORRUPTION(next->prev != prev,
"list_add corruption. next->prev should be prev (%px), but was %px. (next=%px).\n",
prev, next->prev, next) ||
CHECK_DATA_CORRUPTION(prev->next != next,
"list_add corruption. prev->next should be next (%px), but was %px. (prev=%px).\n",
next, prev->next, prev) ||
CHECK_DATA_CORRUPTION(new == prev || new == next,
"list_add double add: new=%px, prev=%px, next=%px.\n",
new, prev, next))
return false;
return true;
}
EXPORT_SYMBOL(__list_add_valid);实践
驱动源码
/*
* bindirect-list
*
* (C) 20179.04.25 <buddy.zhang@aliyun.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
/*
* bidirect-list
*
* +-----------+<--o +-----------+<--o +-----------+<--o +-----------+
* | | | | | | | | | | |
* | prev | o----| prev | o----| prev | o----| prev |
* | list_head | | list_head | | list_head | | list_head |
* | next |---o | next |---o | next |---o | next |
* | | | | | | | | | | |
* +-----------+ o--->+-----------+ o--->+-----------+ o--->+-----------+
*
*/
#include <linux/kernel.h>
#include <linux/init.h>
/* header of list */
#include <linux/list.h>
/* private structure */
struct node {
const char *name;
struct list_head list;
};
/* Initialize a group node structure */
static struct node node0 = { .name = "BiscuitOS_node0", };
/* Declaration and implement a bindirect-list */
LIST_HEAD(BiscuitOS_list);
static __init int bindirect_demo_init(void)
{
struct node *np;
/* Check new entry whether is valid. */
if (__list_add_valid(&node0.list, &BiscuitOS_list,
BiscuitOS_list.next)) {
/* add a new entry on special entry */
__list_add(&node0.list, &BiscuitOS_list, BiscuitOS_list.next);
}
/* Traverser all node on bindirect-list */
list_for_each_entry(np, &BiscuitOS_list, list)
printk("%s\n", np->name);
return 0;
}
device_initcall(bindirect_demo_init);驱动安装
驱动的安装很简单，首先将驱动放到 drivers/BiscuitOS/ 目录下，命名为 list.c， 然后修改 Kconfig 文件，添加内容参考如下：
diff --git a/drivers/BiscuitOS/Kconfig b/drivers/BiscuitOS/Kconfig
index 4edc5a5..1a9abee 100644
--- a/drivers/BiscuitOS/Kconfig
+++ b/drivers/BiscuitOS/Kconfig
@@ -6,4 +6,14 @@ if BISCUITOS_DRV
config BISCUITOS_MISC
bool "BiscuitOS misc driver"
+config BISCUITOS_LIST
+ bool "Bindirect-list"
+
+if BISCUITOS_LIST
+
+config DEBUG_BISCUITOS_LIST
+ bool "__list_add_valid"
+
+endif # BISCUITOS_LIST
+
endif # BISCUITOS_DRV接着修改 Makefile，请参考如下修改：
diff --git a/drivers/BiscuitOS/Makefile b/drivers/BiscuitOS/Makefile
index 82004c9..9909149 100644
--- a/drivers/BiscuitOS/Makefile
+++ b/drivers/BiscuitOS/Makefile
@@ -1 +1,2 @@
obj-$(CONFIG_BISCUITOS_MISC) += BiscuitOS_drv.o
+obj-$(CONFIG_BISCUITOS_LIST) += list.o
--驱动配置
驱动配置请参考下面文章中关于驱动配置一节。在配置中，勾选如下选项，如下：
Device Driver--->
[*]BiscuitOS Driver--->
[*]Bindirect-list
[*]__list_add_valid()具体过程请参考：
驱动编译
驱动编译也请参考下面文章关于驱动编译一节：
驱动运行
驱动的运行，请参考下面文章中关于驱动运行一节：
启动内核，并打印如下信息：
ledtrig-cpu: registered to indicate activity on CPUs
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
BiscuitOS_node0
input: AT Raw Set 2 keyboard as /devices/platform/smb@4000000/smb@4000000:motherboard/smb@4000000:motherboard:iofpga@7,00000000/10006000.kmi/serio0/input/input0
aaci-pl041 10004000.aaci: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24
aaci-pl041 10004000.aaci: FIFO 512 entries驱动分析
每次添加新的节点时候，使用 __list_add_valid() 去检查一个节点是否可用。
附录
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