DTS

Github: atomic_inc

Email: BuddyZhang1 buddy.zhang@aliyun.com

Architecture: ARMv7 Cortex A9-MP

目录

源码分析

#ifndef atomic_inc
#define atomic_inc(v)                   atomic_add(1, (v))
#endif

atomic_inc() 函数用于对 atomic_t 变量加一操作。参数 v 是指向 atomic_t 的指针。 函数直接调用 atomic_add() 函数对 atomic_t 变量增加 1.

atomic_add

atomic_add 源码分析

实践

驱动源码

/*
 * atomic
 *
 * (C) 2019.05.05 <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.
 */

/* Memory access
 *
 *
 *      +----------+
 *      |          |
 *      | Register |                                         +--------+
 *      |          |                                         |        |
 *      +----------+                                         |        |
 *            A                                              |        |
 *            |                                              |        |
 * +-----+    |      +----------+        +----------+        |        |
 * |     |<---o      |          |        |          |        |        |
 * | CPU |<--------->| L1 Cache |<------>| L2 Cache |<------>| Memory |
 * |     |<---o      |          |        |          |        |        |
 * +-----+    |      +----------+        +----------+        |        |
 *            |                                              |        |
 *            o--------------------------------------------->|        |
 *                         volatile/atomic                   |        |
 *                                                           |        |
 *                                                           +--------+
 */

#include <linux/kernel.h>
#include <linux/init.h>

static atomic_t BiscuitOS_counter = ATOMIC_INIT(8);

/* atomic_* */
static __init int atomic_demo_init(void)
{
        /* Atomic value before data  */
        printk("[0]Atomic: oiginal-> %d\n", atomic_read(&BiscuitOS_counter));

        /* Atomic inc */
        atomic_inc(&BiscuitOS_counter);

        /* Atomic value after data  */
        printk("[1]Atomic: new->     %d\n", atomic_read(&BiscuitOS_counter));

        return 0;
}
device_initcall(atomic_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 atomic.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_ATOMIC
+       bool "atomic"
+
+if BISCUITOS_ATOMIC
+
+config DEBUG_BISCUITOS_ATOMIC
+       bool "atomic_inc"
+
+endif # BISCUITOS_ATOMIC
+
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_ATOMIC)  += atomic.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--->
        [*]atomic
            [*]atomic_inc()

具体过程请参考：

Linux 5.0 开发环境搭建 – 驱动配置

驱动编译

驱动编译也请参考下面文章关于驱动编译一节：

Linux 5.0 开发环境搭建 – 驱动编译

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：

Linux 5.0 开发环境搭建 – 驱动运行

启动内核，并打印如下信息：

usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
[0]Atomic: oiginal-> 8
[1]Atomic: new->     9
aaci-pl041 10004000.aaci: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24

驱动分析

便捷的 atomic_t 变量加一操作。

附录

BiscuitOS Home

BiscuitOS Driver

BiscuitOS Kernel Build

Linux Kernel

Bootlin: Elixir Cross Referencer

搭建高效的 Linux 开发环境

赞赏一下吧 🙂

MMU