Email: BuddyZhang1 buddy.zhang@aliyun.com
目录
源码分析
static inline bool ida_is_empty(const struct ida *ida)
{
return radix_tree_empty(&ida->ida_rt);
}ida_is_empty() 函数用于判断 IDA 是否为空。当 IDA radix-tree 为空，那么 IDA 就是空的，所以函数通过调用 radix_tree_empty() 函数检查 IDA radix-tree 是否 为空。
实践
驱动源码
/*
* IDA.
*
* (C) 2019.06.04 <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.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/mm.h>
/* header of IDA/IDR */
#include <linux/idr.h>
#include <linux/radix-tree.h>
/* Root of IDA */
static DEFINE_IDA(BiscuitOS_ida);
static __init int ida_demo_init(void)
{
int id;
if (ida_is_empty(&BiscuitOS_ida))
printk("IDA is empty.\n");
/* Allocate an unused ID */
id = ida_alloc(&BiscuitOS_ida, GFP_KERNEL);
printk("IDA-ID: %#x\n", id);
/* Release an ID */
ida_free(&BiscuitOS_ida, id);
/* Free all IDs */
ida_destroy(&BiscuitOS_ida);
return 0;
}
device_initcall(ida_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 ida.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_IDA
+ bool "IDA"
+
+if BISCUITOS_IDA
+
+config DEBUG_BISCUITOS_IDA
+ bool "ida_is_empty"
+
+endif # BISCUITOS_IDA
+
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_IDA) += ida.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--->
[*]IDA
[*]ida_is_empty()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：
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
IDA is empty.
IDA-ID: 0x0
aaci-pl041 10004000.aaci: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24
aaci-pl041 10004000.aaci: FIFO 512 entries
oprofile: using arm/armv7-ca9驱动分析
检查 IDA 是否为空。
附录
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