為了更好的理解安卓的層次關系,本文在RK3399的安卓系統(tǒng)上增加LED燈的外設,并使用APP打開關閉LED燈。以這樣一個最簡單的實例,來演示從上層到底層的調(diào)用過程。首先從最底層的kernel層開始。
一、驅(qū)動開發(fā)
圖:led燈原理圖
1)設備樹文件(kernel/arch/arm64/boot/dts/rockchip/rk3399-nanopi4-common.dtsi)
test-leds{compatible = "test,leds";led1-work = <&gpio1 23 GPIO_ACTIVE_LOW>;led2-work = <&gpio1 24 GPIO_ACTIVE_LOW>;status = "okay";};
2) 驅(qū)動文件(kernel/drivers/gpio/gpio-testled.c)
MODULE_AUTHOR("embeddedtech");MODULE_LICENSE("Dual BSD/GPL");struct led_data {int led1_pin; //led1引腳int led2_pin; //led2引腳};struct led_data led_info;/** Open the device; in fact, there's nothing to do here.*/int testled_open (struct inode *inode, struct file *filp){return 0;}ssize_t testled_read(struct file *file, char __user *buff, size_t count, loff_t *offp){return 0;}ssize_t testled_write(struct file *file, const char __user *buff, size_t count, loff_t *offp){return 0;}static long testled_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg){switch (cmd) {case LED1CTRL_ON_CMD: {gpio_direction_output(led_info.led1_pin,1);break;}case LED1CTRL_OFF_CMD: {gpio_direction_output(led_info.led1_pin,0);break;}case LED2CTRL_ON_CMD: {gpio_direction_output(led_info.led2_pin,1);break;}case LED2CTRL_OFF_CMD: {gpio_direction_output(led_info.led2_pin,0);break;}default: {printk("testled compat Default %d\n",cmd);break;}}return 0;}long testled_ioctl(struct file *file, unsigned int cmd, unsigned long arg){switch (cmd) {case LED1CTRL_ON_CMD: {gpio_direction_output(led_info.led1_pin,1);break;}case LED1CTRL_OFF_CMD: {gpio_direction_output(led_info.led1_pin,0);break;}case LED2CTRL_ON_CMD: {gpio_direction_output(led_info.led2_pin,1);break;}case LED2CTRL_OFF_CMD: {gpio_direction_output(led_info.led2_pin,0);break;}default: {printk("testled Default %d\n",cmd);break;}}return 0;}static int testled_release(struct inode *node, struct file *file){return 0;}/** Our various sub-devices.*//* Device 0 uses remap_pfn_range */static struct file_operations testled_remap_ops = {.owner = THIS_MODULE,.open = testled_open,.release = testled_release,.read = testled_read,.write = testled_write,.unlocked_ioctl = testled_ioctl,.compat_ioctl = testled_compat_ioctl,};static struct miscdevice testled_misc = {.minor = MISC_DYNAMIC_MINOR,.name = "test-led",.fops = &testled_remap_ops,};/** Module housekeeping.*/static int testled_probe(struct platform_device *pdev){int ret;struct device_node *led_node = pdev->dev.of_node;//enum of_gpio_flags work_flags;ret = misc_register(&testled_misc);if(ret < 0){pr_err("testled_misc_register fails!!!\n");return ret;}led_info.led1_pin = of_get_named_gpio(led_node, "led1-work", 0);if(!gpio_is_valid(led_info.led1_pin)){pr_err("led1 pin invaild: %d",led_info.led1_pin);ret = -ENODEV;goto probe_fail;}ret = gpio_request(led_info.led1_pin, "led1_pin");if(ret < 0){pr_err("led1 pin request failed.");goto probe_fail;}led_info.led2_pin = of_get_named_gpio(led_node, "led2-work", 0);if(!gpio_is_valid(led_info.led2_pin)){pr_err("led2 pin invaild: %d",led_info.led2_pin);ret = -ENODEV;goto probe_fail;}ret = gpio_request(led_info.led2_pin, "led2_pin");if(ret < 0){pr_err("led2 pin request failed.");goto probe_fail;}printk("led1 pin is: %d,led2 pin is: %d",led_info.led1_pin,led_info.led2_pin);return 0;probe_fail:return ret;}static int testled_remove(struct platform_device *pdev){pr_err("testled_misc_remove!!!\n");misc_deregister(&testled_misc);return 0;}static struct of_device_id testled_table[] = {{ .compatible = "test,leds",}, //Compatible node must match dts{ },};static struct platform_driver testled_driver = {.probe = testled_probe,.remove = testled_remove,.driver = {.name = "test_leds",.owner = THIS_MODULE,.of_match_table = testled_table,}};static int testled_init(void){int ret;ret = platform_driver_register(&testled_driver);if(ret < 0)pr_err("platform_register_driver fails!!!\n");pr_err("platform_register_driver succeeds :ret=%d!!!\n",ret);return ret;}static void testled_cleanup(void){platform_driver_unregister(&testled_driver);}module_init(testled_init);module_exit(testled_cleanup);
3)Makefile文件(kernel/drivers/gpio/Makefile)
obj-$(CONFIG_GPIO_TEST_LED) += gpio-testled.o
4) Kconfig文件 (kernel/drivers/gpio/Kconfig)
config GPIO_TEST_LEDbool "select test leds"default y
5)驅(qū)動配置文件(kernel/arch/arm64/configs/nanopi4_nougat_defconfig)
CONFIG_GPIO_TEST_LED=y
6)修改節(jié)點權(quán)限(device/rockchip/common/ueventd.rockchip.rc)
/dev/test_leds 0666 system system
二、驅(qū)動測試
測試代碼gpioleds_test.c
int main(){int i = 0;int dev_fd;dev_fd = open("/dev/test-led",O_RDWR | O_NONBLOCK);if ( dev_fd == -1 ) {printf("Cann't open file /dev/test-led\n");exit(1);}printf("Led1 on\n");ioctl (dev_fd, LED1CTRL_ON_CMD,0);getchar();ioctl (dev_fd, LED1CTRL_OFF_CMD,0);printf("led1 off\n");printf("Led2 on\n");ioctl (dev_fd, LED2CTRL_ON_CMD,0);getchar();ioctl (dev_fd, LED2CTRL_OFF_CMD,0);printf("led2 off\n");close(dev_fd);return 0;}2)Android.mkLOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_SRC_FILES:= \gpioleds_test.cLOCAL_SHARED_LIBRARIES := \liblog \libc \libutils \libcrypto \libhardware \LOCAL_MODULE := gpioleds_testLOCAL_MODULE_TAGS :=LOCAL_MODULE_PATH := $(LOCAL_PATH)LOCAL_CFLAGS +=-D_FORTIFY_SOURCE=0LOCAL_CFLAGS += -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0include $(BUILD_EXECUTABLE
3)編譯成可執(zhí)行文件
mmm external/gpioleds_test/
完成在目錄下生成二進制文件gpioleds_test??截愡M安卓設備。
4)測試
Chmod 777 /data/user/gpioleds_test./ data/user/gpioleds_test
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