hrtimer 사용 例

http://kernel.meizu.com/linux-time.html

 

• hrtimer를 이용하여 timer interrupt 발생하는 예 (kernel module)
• 매 1000ms 마다 interrupt 발생

 

/*
 * example_hrtimer.c
 */

#include <linux/types.h>
#include <linux/module.h>
#include <linux/hrtimer.h>

#define TEST_HRTIMER_PERIOD_MS (1000)
struct hrtimer test_timer;

ulong test_nr_iteration = 0;

enum hrtimer_restart test_irq_timer_handler(struct hrtimer *timer)
{
    BUG_ON(!in_interrupt());

    /*
     * DO SOMETHING
     */
    test_nr_iteration++;

    // reset expire time
    hrtimer_forward_now(timer, ms_to_ktime(TEST_HRTIMER_PERIOD_MS));

    return HRTIMER_RESTART;
}

static int __init example_hrtimer_init(void)
{
    // initialize hrtimer struct
    hrtimer_init(&test_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

    // save hanlder function
    test_timer.function = test_irq_timer_handler;

    // start hrtimer
    hrtimer_start(&test_timer, ms_to_ktime(TEST_HRTIMER_PERIOD_MS), HRTIMER_MODE_REL);

    return 0;
}

static void __exit example_hrtimer_exit(void)
{
    // cancel hrtimer
    hrtimer_cancel(&test_timer);
}

module_init(example_hrtimer_init);
module_exit(example_hrtimer_exit);

MODULE_LICENSE("GPL");

 

아래는 arm64 kernel을 위한 Makefile

# must set kernel build output directory
export KERNEL_DIR=../out

export CUR_DIR=$(PWD)

TARGET_NAME=example_hrtimer
obj-m += $(TARGET_NAME).o

all:
    make ARCH=arm64 LD=aarch64-linux-gnu-ld CC=aarch64-linux-gnu-gcc -C ${KERNEL_DIR} KCFLAGS=$(KCFLAGS) $(EXTRA_CFLAGS) M=$(CUR_DIR) modules

clean:
    make ARCH=arm64 -C ${KERNEL_DIR} M=$(PWD) clean

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