linux dts gpio kernel example

1. dts configuration

./kernel_imx/arch/arm/boot/dts/imx6sl-evk.dts

1. ......  
2. &iomuxc {  
3.         pinctrl-names = "default", "sleep";  
4.         pinctrl-0 = <&pinctrl_hog>;  
5.         pinctrl-1 = <&pinctrl_hog_sleep>;  
6.   
7.         hog {  
8.                 pinctrl_hog: hoggrp {  
9.                         fsl,pins = <  
10.                                 MX6SL_PAD_KEY_ROW7__GPIO4_IO07    0x17059  
11.                                 MX6SL_PAD_KEY_COL7__GPIO4_IO06    0x17059  
12.                                 MX6SL_PAD_SD2_DAT7__GPIO5_IO00    0x17059  
13.                                 MX6SL_PAD_SD2_DAT6__GPIO4_IO29    0x17059  
14.                                 MX6SL_PAD_REF_CLK_32K__GPIO3_IO22 0x17059  
15.                                 MX6SL_PAD_FEC_TX_CLK__GPIO4_IO21  0x80000000  
16.                                 MX6SL_PAD_KEY_ROW5__GPIO4_IO03    0x110b0  
17.                                 MX6SL_PAD_EPDC_VCOM0__GPIO2_IO03  0x80000000  
18.                                 MX6SL_PAD_EPDC_PWRSTAT__GPIO2_IO13 0x80000000  
19.                                 MX6SL_PAD_EPDC_PWRCTRL0__GPIO2_IO07 0x4001b0b0 /*luke modify 20161125*/  
20.                                 MX6SL_PAD_EPDC_PWRWAKEUP__GPIO2_IO14 0x80000000  
21.                                 MX6SL_PAD_EPDC_PWRINT__GPIO2_IO12 0x80000000  
22.                                 MX6SL_PAD_EPDC_PWRCTRL3__GPIO2_IO10 0x170b0  
23.                                 MX6SL_PAD_EPDC_PWRCTRL2__GPIO2_IO09 0x80000000  
24.                                 MX6SL_PAD_KEY_COL6__GPIO4_IO04    0x110b0  
25.                                 MX6SL_PAD_ECSPI2_MISO__GPIO4_IO14 0x17000  
26.                                 MX6SL_PAD_ECSPI2_MOSI__GPIO4_IO13 0x17000  
27.                                 MX6SL_PAD_ECSPI2_SS0__GPIO4_IO15  0x17000  
28.                                 MX6SL_PAD_FEC_RX_ER__GPIO4_IO19   0x1b0b0  
29.                                 MX6SL_PAD_LCD_RESET__GPIO2_IO19 0x1b0b0  
30.                                 MX6SL_PAD_KEY_COL4__GPIO4_IO00  0x80000000  
31.                                 MX6SL_PAD_KEY_COL5__GPIO4_IO02  0x80000000  
32.                         >;  
33.                 };  
34.   
35.                 pinctrl_hog_sleep: hoggrp_sleep {  
36.                         fsl,pins = <  
37.                                 MX6SL_PAD_KEY_ROW5__GPIO4_IO03    0x3080  
38.                                 MX6SL_PAD_KEY_COL6__GPIO4_IO04    0x3080  
39.                                 MX6SL_PAD_LCD_RESET__GPIO2_IO19   0x3080  
40.                         >;  
41.                 };  
42.         };  
43. };  
44. ......  

./kernel_imx/arch/arm/boot/dts/imx6sl-evk-common.dtsi

1. ......  
2.       /*luke add hello gpio test 20161125*/  
3.        hello-led {  
4.                  compatible = "firefly,hello_led";  
5.                  led = <&gpio2 7 0>;  
6.                  status = "okay";  
7.          };   
8. ......  

2. kernel module

2.1 add .c file

./kernel_imx/drivers/hello_led_module/hello.c

#include
#include
#include
#include
#include

#ifdef CONFIG_OF
#include
#include
#include
#endif


#define GPIO_LOW 0
#define GPIO_HIGH 1

static int firefly_hello_probe(struct platform_device *pdev)
{
    int ret = -1;
    int i;
    int gpio,flag;
    struct device_node *hello_node = pdev->dev.of_node;

    printk(KERN_INFO "%s() enter line:%d\n",__FUNCTION__,__LINE__);

    gpio = of_get_named_gpio_flags(hello_node,"led", 0,&flag);
    if (!gpio_is_valid(gpio)){
        printk(KERN_INFO "hello: invalid gpio : %d\n",gpio);
        return -1;
    }
    ret = gpio_request(gpio, "hello_led");
    if (ret != 0) {
        gpio_free(gpio);
        printk(KERN_INFO "hello: invalid request : %d\n",gpio);
        return -EIO;
    }

    gpio_direction_output(gpio, GPIO_HIGH);

    for(i=0; i < 10; i++)
    {
        gpio_set_value(gpio,GPIO_LOW);
        mdelay(500);
        gpio_set_value(gpio,GPIO_HIGH);
        mdelay(500);
    }

    printk(KERN_INFO "%s() exit line:%d\n",__FUNCTION__,__LINE__);

    return 0;  //return Ok
}


static int firefly_hello_remove(struct platform_device *pdev)
{
    struct device_node *hello_node = pdev->dev.of_node;
        int gpio,flag;
    gpio = of_get_named_gpio_flags(hello_node,"led", 0,&flag);
    if (!gpio_is_valid(gpio)){
        printk(KERN_INFO "hello: invalid gpio : %d\n",gpio);
        return -1;
    }
        gpio_free(gpio);
    return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id of_firefly_hello_match[] = {
    { .compatible = "firefly,hello_led" },
    { /* Sentinel */ }
};
#endif

static struct platform_driver firefly_hello_driver = {
    .probe      = firefly_hello_probe,
    .remove     = firefly_hello_remove,
    .driver     = {
        .name   = "firefly_hello",
        .owner  = THIS_MODULE,
#ifdef CONFIG_OF
        .of_match_table = of_match_ptr(of_firefly_hello_match),
#endif
    },

};

static int __init hello_init(void)
{
    printk(KERN_INFO "Enter %s\n", __FUNCTION__);
    return platform_driver_register(&firefly_hello_driver);
}

static void __exit hello_exit(void)
{
    platform_driver_unregister(&firefly_hello_driver);
    printk("Exit Hello world\n");
}

module_init(hello_init);
module_exit(hello_exit);

MODULE_AUTHOR("sai <[e-mail]>");
MODULE_DESCRIPTION("Firefly hello driver");
MODULE_LICENSE("GPL");

ps: we can also ignore dev_node and of_get_named_gpio_flags() if use 37(GPIO2_IO07=32+7=39) directly.

2.2 add Makefile

./kernel_imx/drivers/hello_led_module/Makefile

1. PWD = $(shell pwd)  
2. KERNEL_SRC = /home/xxx/Projects/Android/android4.4.3/kernel_imx/  
3. CROSS_COMPILE = /home/xxx/Projects/Android/android4.4.3/prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.7/bin/arm-linux-androideabi-  
4.   
5. obj-m := hello.o  
6. all:  
7.         make ARCH=arm CFLAGS_MODULE=-fno-pic  CROSS_COMPILE=$(CROSS_COMPILE) -C $(KERNEL_SRC) M=$(PWD) modules  
8. clean:  
9.         make ARCH=arm CROSS_COMPILE=$(CROSS_COMPILE) -C $(KERNEL_SRC) M=$(PWD) clean  

2.3 compile

cd ./kernel_imx/driver/hello_module

make

3. result