#define WRITE_ONCE(x, val) \
({                                                      \
        union { typeof(x) __val; char __c[1]; } __u =   \
                { .__val = (__force typeof(x)) (val) }; \
        __write_once_size(&(x), __u.__c, sizeof(x));    \
        __u.__val;                                      \
})

/*
 * 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.
 */

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

/* READ_ONCE/WRITE_ONCE */
#include <linux/compiler.h>

volatile char ch;

static __init int atomic_demo_init(void)
{
	char cb  = 'A';

	/* Write data into memory not cache/buffer/register */
	WRITE_ONCE(ch, cb);

	/* Read from memory not cache nor register */
	cb = READ_ONCE(ch);

	printk("cb: %c\n", cb);

	return 0;
}
device_initcall(atomic_demo_init);

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 "WRITE_ONCE"
+
+endif # BISCUITOS_ATOMIC
+
endif # BISCUITOS_DRV

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
--

Device Driver--->
    [*]BiscuitOS Driver--->
        [*]atomic
            [*]WRITE_ONCE()

usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
cb: A
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