linux 标准GPIO 驱动模型—version1

前言：本文主要介绍gpio driver实现基本方法，具体实例在后续的文章中继续介绍

Index:

1、bus 概念介绍

2、Device 与driver匹配过

3、GPIO driver 实现标准框架图

4、GPIO driver 细化实现

5、GPIO 上层应用

1、bus 概念介绍

Bus（platform总线）：总线是CPU和一个或多个设备之间信息交互的通道。而为了方便模型的抽象，所有的设备都应连接到总线上

Device（gpio设备）：抽象系统中所有的硬件设备，描述它的名字、属性、从属的Bus。

Device Driver（gpio驱动）：Linux设备模型用Driver抽象硬件设备的驱动程序，它包含设备初始化、ops相关的接口实现。

2、Device 与driver匹配过程

系统启动Bus init：kernel_init()à do_basic_setup()à driver_init()àplatform_bus_init()

设备注册到内核：platform_device_registeràplatform_device_add挂在platform bus下

驱动注册到内核：platform_driver_registeràdriver_register-àbus_add_driverà

driver_attachàbus_for_each_dev(drv->bus,NULL,drv,__driver_attach)à__driver_attach

àdriver_match_device--àdrv->bus->match==platform_match()->

strncmp(pdev->name,drv->name, BUS_ID_SIZE)

如果相符就调用platform_drv_probe()->driver->probe()，如果probe成功则绑定该设备到该驱动

其实注册dev 时候也会prove driver.

static int platform_match(struct device *dev, struct device_driver *drv)
{	
	struct platform_device *pdev = to_platform_device(dev);
	struct platform_driver *pdrv = to_platform_driver(drv);
    ……
        printk ("platform_match--driver_match_device-pdev->name=%s,drv->name=%s;\n", pdev->name, drv->name);
	return (strcmp(pdev->name, drv->name) == 0);
}

实际举例：

static struct platform_device codec_device_test0 = {
	.name		= "test-codec-test0",
	.id		= 0,		
};
static struct platform_device *alsa_devices_test[] __initdata =
{
&codec_device_test0,
};
platform_device_register (alsa_devices_test);

static struct platform_driver mdp_codec_driver = {
    .driver     = {
        .name       = “test-codec-test0", 
        .owner      = THIS_MODULE,
        .of_match_table = of_match_ptr(mdp_audio_codec_dt_match),
    },
    .probe      = mdp_codec_device_probe,
    .remove     = mdp_codec_device_remove,
};
platform_driver_register(&mdp_codec_driver);

注：经过上面的dev,drvregister platform就可以match到

3、GPIO driver 实现标准框架图

GPIOLIB:

Driver 具体实现call pinctrl_request_gpio(/3.10.23/drivers/gpio/gpio-pl061.c)

gpiochip_add_pin_rangeàpinctrl_find_and_add_gpio_range

Device Tree:

/3.10.23/drivers/of/souce files

/3.10.23/arch/arm/boot/dts/格式组织reg

/3.10.23/Documentation/devicetree/bindings/gpio/gpio.txt

Machine driver：pin ctrl下级控制，具体没有查看

4、GPIO 细化实现

    在LINUX里实现了对GPIO操作的统一接口，这个接口实则上就是GPIO驱动的框架，具体的实现文件为gpiolib.c

  编译配置：

//THEALE/RedLion/3.10.23/drivers/gpio/Kconfig

//THEALE/RedLion/3.10.23/.config

CONFIG_ARCH_HAVE_CUSTOM_GPIO_H=y
CONFIG_ARCH_WANT_OPTIONAL_GPIOLIB=y
CONFIG_GPIO_DEVRES=y
CONFIG_GPIOLIB=y
CONFIG_GPIO_SYSFS=y

menuconfig GPIOLIB
        bool "GPIO Support"
        depends on ARCH_WANT_OPTIONAL_GPIOLIB || ARCH_REQUIRE_GPIOLIB
        help
config OF_GPIO
        def_bool y
        depends on OF  //device tree
config GPIO_SYSFS
        bool "/sys/class/gpio/... (sysfs interface)"
        depends on SYSFS
        help

gpio_desc结构体中:

gpio_chip指向硬件层的GPIO

flags为一标志位，用来指示当前GPIO是否已经占用

label是一个字符串指针，用来作说明

gpio_chip结构体:

ngpio指定个数

base为起始的GPIO号

gpiochip_add注册一个gpio_chip对应的gpio_desc到全局数组gpio描述符中。一个描述符对应一个GPIO

//THEALE/RedLion/3.10.23/drivers/gpio/gpiolib.c

struct gpio_desc {
        struct gpio_chip        *chip;
        unsigned long           flags;
        const char              *label;
};

GPIO  数据结构：//THEALE/RedLion/3.10.23/include/asm-generic/gpio.h

Struct gpio_chip {	
        …….
 int                     (*request)(struct gpio_chip *chip,
                                                unsigned offset);
        void                    (*free)(struct gpio_chip *chip,
                                                unsigned offset);
        int                     (*get_direction)(struct gpio_chip *chip,
                                                unsigned offset);
        int                     (*direction_input)(struct gpio_chip *chip,
                                                unsigned offset);
        int                     (*get)(struct gpio_chip *chip,
                                                unsigned offset);
        int                     (*direction_output)(struct gpio_chip *chip,
                                                unsigned offset, int value);
        int                     (*set_debounce)(struct gpio_chip *chip,
                                                unsigned offset, unsigned debounce);
        void                    (*set)(struct gpio_chip *chip,
                                                unsigned offset, int value);
        int                     (*to_irq)(struct gpio_chip *chip,
                                                unsigned offset);
        int                     base;
        u16                     ngpio;
        ………
}

申请和释放GPIO资源：

Extern int gpio_request(unsignedgpio, const char *label);

Extern void gpio_free(unsignedgpio);

设置GPIO口方向的操作：

Extern int gpio_direction_input(unsignedgpio);

Extern int gpio_direction_output(unsignedgpio, int value);

设置GPIO口高低电平值操作：

Extern int gpio_get_value_cansleep(unsignedgpio);

Extern void gpio_set_value_cansleep(unsigned gpio, int value);

Extern int __gpio_get_value(unsigned gpio);

Extern void __gpio_set_value(unsigned gpio, intvalue);

检测GPIO 是否有效及中断

 int gpio_is_valid(int number); 

 int gpio_to_irq(unsigned gpio); àrequest_irq()和free_irq()

5、GPIO 上层应用

//THEALE/RedLion/3.10.23/Documentation/gpio.txt  .“Paths in Sysfs”

int gpio_export(unsigned gpio, bool direction_may_change);

void gpio_unexport(); 

/sys/class/gpio目录下的三种文件： 

  --export/unexport文件

  --gpioN指代具体的gpio引脚

 --gpio_chipN指代gpio控制器

 echo 19 > export ----》/sys/class/gpio/gpio19--》

       direction

value 

edge 

echo 19 > unexport—》注销

GPIOcontrol (read_only)

/sys/class/gpio/gpiochipN/

             "base" ... same as N, the firstGPIO managed by this chip

             "label" ... provided fordiagnostics (not always unique)

             "ngpio" ... how many GPIOsthis manges (N to N + ngpio - 1)

测试Demo 程序：

 #include <stdio.h>
 #include <unistd.h>
 #include <sys/stat.h>
 #include <linux/fs.h>
 #include <fcntl.h>
 #include <string.h>
 #include <termios.h>
 #include <sys/ioctl.h>
 
 int main(int argc, char **argv)
 {
     int Mgpio_fd = -1;
     char Mgpio_on[] = "1";
     char Mgpio_num[]="110";
     char Mgpio_dir[]="out";

     printf("test gpio start!\n");
     Mgpio_fd = open("/sys/class/gpio/export", O_WRONLY);
     write(Mgpio_fd, Mgpio_num, strlen(Mgpio_num));
     close(Mgpio_fd);

     Mgpio_fd = open("/sys/class/gpio/gpio110/direction", O_RDWR);
     write(Mgpio_fd, Mgpio_dir, strlen(Mgpio_dir));
     close(Mgpio_fd);
 
     Mgpio_fd = open("/sys/class/gpio/gpio110/value", O_RDWR);
     write(Mgpio_fd, Mgpio_on, strlen(Mgpio_on));
     close(Mgpio_fd);
 
     Mgpio_fd = open("/sys/class/gpio/unexport",O_WRONLY);
     write(Mgpio_fd, Mgpio_num, strlen(Mgpio_num));
     close(Mgpio_fd);
 
     printf("test gpio end!\n");
     return 0;
}