linux内核的gpiolib详解

#include <linux/init.h>            // __init   __exit
#include <linux/module.h>      // module_init  module_exit
#include <mach/regs-gpio.h>
#include <mach/gpio-bank.h>

#include <asm/io.h>     //writel

#include <mach/gpio.h>
#include <linux/leds.h>
#include <asm/string.h> 

#define X210_LED_OFF 1U
#define X210_LED_ON  0U

struct led_classdev    cdev1;
struct led_classdev cdev2;
struct led_classdev cdev3;

void s5pv210_led1_set(struct led_classdev *led_cdev,enum led_brightness brightness);
void s5pv210_led2_set(struct led_classdev *led_cdev,enum led_brightness brightness);
void s5pv210_led3_set(struct led_classdev *led_cdev,enum led_brightness brightness);

static struct gpio x210_led_gpio[] =
{
    { S5PV210_GPJ0(), GPIOF_OUT_INIT_HIGH,  "LED1" }, /* default to OFF */
    { S5PV210_GPJ0(), GPIOF_OUT_INIT_HIGH,  "LED2" }, /* default to OFF */
    { S5PV210_GPJ0(), GPIOF_OUT_INIT_HIGH,  "LED3" } /* default to OFF */
};
void s5pv210_led1_set(struct led_classdev *led_cdev,enum led_brightness brightness)
{
    printk(KERN_INFO "s5pv210_led1_set successful %d\n",brightness);
    if(brightness == LED_OFF)
    {
        gpio_set_value(x210_led_gpio[].gpio,X210_LED_OFF);
    }
    else
    {
        gpio_set_value(x210_led_gpio[].gpio,X210_LED_ON);

    }
}
void s5pv210_led2_set(struct led_classdev *led_cdev,enum led_brightness brightness)
{
    printk(KERN_INFO "s5pv210_led2_set successful %d\n",brightness);
    if(brightness == LED_OFF)
    {
        gpio_set_value(x210_led_gpio[].gpio,X210_LED_OFF);
    }
    else
    {
        gpio_set_value(x210_led_gpio[].gpio,X210_LED_ON);

    }
}
void s5pv210_led3_set(struct led_classdev *led_cdev,enum led_brightness brightness)
{
    printk(KERN_INFO "s5pv210_led3_set successful %d\n",brightness);
    if(brightness == LED_OFF)
    {
        gpio_set_value(x210_led_gpio[].gpio,X210_LED_OFF);
    }
    else
    {
        gpio_set_value(x210_led_gpio[].gpio,X210_LED_ON);

    }

}
static int __init s5pv210_led_init(void)
{
    int ret = -;
    printk(KERN_INFO "s5pv210_led_init successful \n");
    cdev1.brightness_set = s5pv210_led1_set;
    cdev1.name = "led1";
    ret = led_classdev_register(NULL, &cdev1);
    if (ret < )
    {
        printk(KERN_WARNING "led_classdev_register fail \n");
        goto reg_err1;
    }

    cdev2.brightness_set = s5pv210_led2_set;
    cdev2.name = "led2";
    ret = led_classdev_register(NULL, &cdev2);
    if (ret < )
    {
        printk(KERN_WARNING "led_classdev_register fail \n");
        goto reg_err2;
    }

    cdev3.brightness_set = s5pv210_led3_set;
    cdev3.name = "led3";
    ret = led_classdev_register(NULL, &cdev3);
    if (ret < )
    {
        printk(KERN_WARNING "led_classdev_register fail \n");
        goto reg_err3;
    }
    ret = gpio_request_array(x210_led_gpio, ARRAY_SIZE(x210_led_gpio));
    if (ret)
    {
        goto gpio_err;
    }

    return ;

gpio_err:
    led_classdev_unregister(&cdev3);

reg_err3:
    led_classdev_unregister(&cdev2);

reg_err2:
    led_classdev_unregister(&cdev1);

reg_err1:
    return ret;
}

static void __exit s5pv210_led_exit(void)
{
    printk(KERN_INFO "s5pv210_led_exit successful \n");
    gpio_free_array(x210_led_gpio, ARRAY_SIZE(x210_led_gpio));

    led_classdev_unregister(&cdev1);
    led_classdev_unregister(&cdev2);
    led_classdev_unregister(&cdev3);

}

module_init(s5pv210_led_init);
module_exit(s5pv210_led_exit);

// MODULE_xxx这种宏作用是用来添加模块描述信息
MODULE_LICENSE("GPL");                // 描述模块的许可证
MODULE_AUTHOR("musk");                // 描述模块的作者
MODULE_DESCRIPTION("x210 LED driver");    // 描述模块的介绍信息
MODULE_ALIAS("led_driver");            // 描述模块的别名信息

一. 什么是gpiolib

1.1. linux中从2.6.35以后就开始有gpiolib库了，gpiolib的作用是对所有的gpio实行统一管理,因为驱动在工作的时候，会出现好几个驱动共同使用同一个gpio的情况；这会造成混乱。所以内核提供了一些方法来管理gpio资源；

二. gpiolib在内核中实现流程

2.1. gpiolib初始化哪里

2.1.1. smdkc110_map_io函数是gpiolib初始化的入口

a. 前面介绍虚拟地址映射时，介绍过下面的结构体在linux初始化会被调用。其中smdkc110_map_io我们值得关注。

#ifdef CONFIG_MACH_SMDKC110
MACHINE_START(SMDKC110, "SMDKC110")
#elif CONFIG_MACH_SMDKV210
MACHINE_START(SMDKV210, "SMDKV210")
#endif
    /* Maintainer: Kukjin Kim <kgene.kim@samsung.com> */
    .phys_io    = S3C_PA_UART & 0xfff00000,
    .io_pg_offst    = (((u32)S3C_VA_UART) >> ) & 0xfffc,
    .boot_params    = S5P_PA_SDRAM + 0x100,
    //.fixup        = smdkv210_fixup,
    .init_irq    = s5pv210_init_irq,
    .map_io        = smdkc110_map_io,
    .init_machine    = smdkc110_machine_init,
    .timer        = &s5p_systimer,

b. s5pv210_gpiolib_init的调用就会初始化gpiolib

static void __init smdkc110_map_io(void)
{
    s5p_init_io(NULL, , S5P_VA_CHIPID);                 //  静态物理地址到虚拟地址的映射初始化
    s3c24xx_init_clocks();                          //   系统时钟初始化
    s5pv210_gpiolib_init();                                       //   gpiolib管理器初始化
    s3c24xx_init_uarts(smdkc110_uartcfgs, ARRAY_SIZE(smdkc110_uartcfgs));
    s5p_reserve_bootmem(smdkc110_media_devs, ARRAY_SIZE(smdkc110_media_devs));
#ifdef CONFIG_MTD_ONENAND
    s5pc110_device_onenand.name = "s5pc110-onenand";
#endif
#ifdef CONFIG_MTD_NAND
    s3c_device_nand.name = "s5pv210-nand";
#endif
    s5p_device_rtc.name = "smdkc110-rtc";
}

2.1.2. s5pv210_gpiolib_init函数

a. 函数中有个重要结构体函数s5pv210_gpio_4bit。这个我们后面讲

b. samsung_gpiolib_add_4bit_chips这个函数用于挂载硬件数据到内核中

__init int s5pv210_gpiolib_init(void)
{
    struct s3c_gpio_chip *chip = s5pv210_gpio_4bit;    //  4bit表示的是一个gpio使用4位来配置描述     s5pv210_gpio_4bit是一个struct s3c_gpio_chip数组，是三星移植时写好的
    int nr_chips = ARRAY_SIZE(s5pv210_gpio_4bit);     //  获取端口数量(注意一组端口和一个具体的gpio)
    int i = ;

    for (i = ; i < nr_chips; i++, chip++) {
        if (chip->config == NULL)              //  如果我们的gpio端口没有  配置方法  则使用  gpio_cfg  进行默认配置
            chip->config = &gpio_cfg;
        if (chip->base == NULL)                 //  如果我们的gpio端口结构体中没有填充 基准编号   则使用下面进行填充
            chip->base = S5PV210_BANK_BASE(i);
    }

    samsung_gpiolib_add_4bit_chips(s5pv210_gpio_4bit, nr_chips);   //  添加gpiolib

    return ;
}

2.2. 与硬件相关函数

2.2.1.  samsung_gpiolib_4bit_input&samsung_gpiolib_4bit_output函数

a. 这个函数是真正进行寄存器操作的函数，最终驱动工程师进行io设置时会间接指向该函数指针

/* The samsung_gpiolib_4bit routines are to control the gpio banks where
 * the gpio configuration register (GPxCON) has 4 bits per GPIO, as the
 * following example:
 *
 * base + 0x00: Control register, 4 bits per gpio
 *        gpio n: 4 bits starting at (4*n)
 *        0000 = input, 0001 = output, others mean special-function
 * base + 0x04: Data register, 1 bit per gpio
 *        bit n: data bit n
 *
 * Note, since the data register is one bit per gpio and is at base + 0x4
 * we can use s3c_gpiolib_get and s3c_gpiolib_set to change the state of
 * the output.
*/

static int samsung_gpiolib_4bit_input(struct gpio_chip *chip,
                      unsigned int offset)
{
    struct s3c_gpio_chip *ourchip = to_s3c_gpio(chip);
    void __iomem *base = ourchip->base;
    unsigned long con;

    con = __raw_readl(base + GPIOCON_OFF);
    con &= ~(0xf << con_4bit_shift(offset));
    __raw_writel(con, base + GPIOCON_OFF);

    gpio_dbg("%s: %p: CON now %08lx\n", __func__, base, con);

    return ;
}
static int samsung_gpiolib_4bit_output(struct gpio_chip *chip,
                       unsigned int offset, int value)
{
    struct s3c_gpio_chip *ourchip = to_s3c_gpio(chip);
    void __iomem *base = ourchip->base;
    unsigned long con;
    unsigned long dat;

    con = __raw_readl(base + GPIOCON_OFF);
    con &= ~(0xf << con_4bit_shift(offset));
    con |= 0x1 << con_4bit_shift(offset);

    dat = __raw_readl(base + GPIODAT_OFF);

    if (value)
        dat |=  << offset;
    else
        dat &= ~( << offset);

    __raw_writel(dat, base + GPIODAT_OFF);
    __raw_writel(con, base + GPIOCON_OFF);
    __raw_writel(dat, base + GPIODAT_OFF);

    gpio_dbg("%s: %p: CON %08lx, DAT %08lx\n", __func__, base, con, dat);

    return ;
}

 2.2.2. gpio_get_value & gpio_set_value

a. 这两个红替代gpio的读取和设置函数。一般函数前加"_"或"__"是给内核调用的，这里使用宏定义就很好的避免了驱动开发调用内核调用的函数

b. 这个函数也是真正进行寄存器操作的函数，最终驱动工程师进行io读写时也会间接指向该函数指针

#define gpio_get_value __gpio_get_value
#define gpio_set_value __gpio_set_value

/**
 * __gpio_get_value() - return a gpio's value
 * @gpio: gpio whose value will be returned
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_get_value().
 * It returns the zero or nonzero value provided by the associated
 * gpio_chip.get() method; or zero if no such method is provided.
 */
int __gpio_get_value(unsigned gpio)
{
    struct gpio_chip    *chip;

    chip = gpio_to_chip(gpio);
    WARN_ON(extra_checks && chip->can_sleep);
    return chip->get ? chip->get(chip, gpio - chip->base) : ;
}

/**
 * __gpio_set_value() - assign a gpio's value
 * @gpio: gpio whose value will be assigned
 * @value: value to assign
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_set_value().
 * It invokes the associated gpio_chip.set() method.
 */
void __gpio_set_value(unsigned gpio, int value)
{
    struct gpio_chip    *chip;

    chip = gpio_to_chip(gpio);
    WARN_ON(extra_checks && chip->can_sleep);
    chip->set(chip, gpio - chip->base, value);
}

    2.3. gpiolib的attribute部分

2.3.1. attribute用于定义文件的属性，当我们echo 和cat时都由其决定

2.3.2. 源码中export_store&unexport_store函数与查看gpio的其他属性有关，比如查看IO电平值等。。。

2.3.3. CONFIG_GPIO_SYSFS该宏决定是否开启gpiolib的attribute部分。可以在menuconfig进行配置

[root@musk210 led3]# cd /sys/class/gpio/                                                         //shell测试结果
[root@musk210 gpio]# ls
export       gpiochip164  gpiochip235  gpiochip316  gpiochip396  gpiochip56
gpiochip0    gpiochip172  gpiochip244  gpiochip325  gpiochip40   gpiochip62
gpiochip104  gpiochip181  gpiochip253  gpiochip334  gpiochip405  gpiochip71
gpiochip112  gpiochip188  gpiochip262  gpiochip343  gpiochip414  gpiochip80
gpiochip120  gpiochip197  gpiochip271  gpiochip35   gpiochip423  gpiochip89
gpiochip128  gpiochip206  gpiochip280  gpiochip351  gpiochip431  gpiochip9
gpiochip137  gpiochip212  gpiochip289  gpiochip360  gpiochip438  gpiochip96
gpiochip14   gpiochip221  gpiochip29   gpiochip369  gpiochip447  unexport
gpiochip146  gpiochip226  gpiochip298  gpiochip378  gpiochip456
gpiochip155  gpiochip23   gpiochip307  gpiochip387  gpiochip47
[root@musk210 gpio]# cd gpiochip0
[root@musk210 gpiochip0]# ls
base       label      ngpio      power      subsystem  uevent
[root@musk210 gpiochip0]# cat base 

[root@musk210 gpiochip0]# echo  > base
-sh: can't create base: Permission denied
[root@musk210 gpiochip0]#                                                                      // shell测试 end

/*
 * /sys/class/gpio/gpiochipN/
 *   /base ... matching gpio_chip.base (N)
 *   /label ... matching gpio_chip.label
 *   /ngpio ... matching gpio_chip.ngpio
 */

static ssize_t chip_base_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
{
    const struct gpio_chip    *chip = dev_get_drvdata(dev);

    return sprintf(buf, "%d\n", chip->base);
}
static DEVICE_ATTR(base, , chip_base_show, NULL);

static ssize_t chip_label_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
{
    const struct gpio_chip    *chip = dev_get_drvdata(dev);

    return sprintf(buf, "%s\n", chip->label ? : "");
}
static DEVICE_ATTR(label, , chip_label_show, NULL);

static ssize_t chip_ngpio_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
{
    const struct gpio_chip    *chip = dev_get_drvdata(dev);

    return sprintf(buf, "%u\n", chip->ngpio);
}
static DEVICE_ATTR(ngpio, , chip_ngpio_show, NULL);

static const struct attribute *gpiochip_attrs[] = {
    &dev_attr_base.attr,
    &dev_attr_label.attr,
    &dev_attr_ngpio.attr,
    NULL,
};

static const struct attribute_group gpiochip_attr_group = {
    .attrs = (struct attribute **) gpiochip_attrs,
};

2.4. linux中查看gpio使用情况

2.4.1. 使用方法：mount -t debugfs debugfs /tmp，然后cat /tmp/gpio即可得到gpio的所有信息

2.4.2. 使用完后umount /tmp卸载掉debugfs

三. struct s3c_gpio_chip s5pv210_gpio_4bit[]

3.1. 这个结构体数据就是三星SOC厂商编写的code,把SOC是所有的port，虚拟地址，操作function和内核挂接起来

3.1.1. 这里讲解下*base与base

a. struct s3c_gpio_chip结构体下的*base是每个port起始虚拟地址

b. struct gpio_chip结构体下的base可以理解为每个port下具体IO的编号。这个编号从小到大排列，可以是不连续单必须唯一，这样可以定位到每个IO口上

/**
 * struct s3c_gpio_chip - wrapper for specific implementation of gpio
 * @chip: The chip structure to be exported via gpiolib.
 * @base: The base pointer to the gpio configuration registers.
 * @config: special function and pull-resistor control information.
 * @lock: Lock for exclusive access to this gpio bank.
 * @pm_save: Save information for suspend/resume support.
 *
 * This wrapper provides the necessary information for the Samsung
 * specific gpios being registered with gpiolib.
 *
 * The lock protects each gpio bank from multiple access of the shared
 * configuration registers, or from reading of data whilst another thread
 * is writing to the register set.
 *
 * Each chip has its own lock to avoid any  contention between different
 * CPU cores trying to get one lock for different GPIO banks, where each
 * bank of GPIO has its own register space and configuration registers.
 */
struct s3c_gpio_chip {
    struct gpio_chip    chip;
    struct s3c_gpio_cfg    *config;
    struct s3c_gpio_pm    *pm;
    void __iomem        *base;
    int            eint_offset;
    spinlock_t         lock;
#ifdef CONFIG_PM
    u32            pm_save[];
#endif
};

/**
 * struct gpio_chip - abstract a GPIO controller
 * @label: for diagnostics
 * @dev: optional device providing the GPIOs
 * @owner: helps prevent removal of modules exporting active GPIOs
 * @request: optional hook for chip-specific activation, such as
 *    enabling module power and clock; may sleep
 * @free: optional hook for chip-specific deactivation, such as
 *    disabling module power and clock; may sleep
 * @direction_input: configures signal "offset" as input, or returns error
 * @get: returns value for signal "offset"; for output signals this
 *    returns either the value actually sensed, or zero
 * @direction_output: configures signal "offset" as output, or returns error
 * @set: assigns output value for signal "offset"
 * @to_irq: optional hook supporting non-static gpio_to_irq() mappings;
 *    implementation may not sleep
 * @dbg_show: optional routine to show contents in debugfs; default code
 *    will be used when this is omitted, but custom code can show extra
 *    state (such as pullup/pulldown configuration).
 * @base: identifies the first GPIO number handled by this chip; or, if
 *    negative during registration, requests dynamic ID allocation.
 * @ngpio: the number of GPIOs handled by this controller; the last GPIO
 *    handled is (base + ngpio - 1).
 * @can_sleep: flag must be set iff get()/set() methods sleep, as they
 *    must while accessing GPIO expander chips over I2C or SPI
 * @names: if set, must be an array of strings to use as alternative
 *      names for the GPIOs in this chip. Any entry in the array
 *      may be NULL if there is no alias for the GPIO, however the
 *      array must be @ngpio entries long.  A name can include a single printk
 *      format specifier for an unsigned int.  It is substituted by the actual
 *      number of the gpio.
 *
 * A gpio_chip can help platforms abstract various sources of GPIOs so
 * they can all be accessed through a common programing interface.
 * Example sources would be SOC controllers, FPGAs, multifunction
 * chips, dedicated GPIO expanders, and so on.
 *
 * Each chip controls a number of signals, identified in method calls
 * by "offset" values in the range 0..(@ngpio - 1).  When those signals
 * are referenced through calls like gpio_get_value(gpio), the offset
 * is calculated by subtracting @base from the gpio number.
 */
struct gpio_chip {
    const char        *label;
    struct device        *dev;
    struct module        *owner;

    int            (*request)(struct gpio_chip *chip,
                        unsigned offset);
    void            (*free)(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);

    void            (*dbg_show)(struct seq_file *s,
                        struct gpio_chip *chip);
    int            base;
    u16            ngpio;
    const char        *const *names;
    unsigned        can_sleep:;
    unsigned        exported:;
};
/*
 * Following are the gpio banks in v210.
 *
 * The 'config' member when left to NULL, is initialized to the default
 * structure gpio_cfg in the init function below.
 *
 * The 'base' member is also initialized in the init function below.
 * Note: The initialization of 'base' member of s3c_gpio_chip structure
 * uses the above macro and depends on the banks being listed in order here.
 */
static struct s3c_gpio_chip s5pv210_gpio_4bit[] = {
    {
        .chip    = {
            .base    = S5PV210_GPA0(),
            .ngpio    = S5PV210_GPIO_A0_NR,
            .label    = "GPA0",
            .to_irq = s5p_gpiolib_gpioint_to_irq,
        },
    }, {
        .chip    = {
            .base    = S5PV210_GPA1(),
            .ngpio    = S5PV210_GPIO_A1_NR,
            .label    = "GPA1",
            .to_irq = s5p_gpiolib_gpioint_to_irq,
        },
    }, {
        .chip    = {
            .base    = S5PV210_GPB(),
            .ngpio    = S5PV210_GPIO_B_NR,
            .label    = "GPB",
            .to_irq = s5p_gpiolib_gpioint_to_irq,
        },
    }, {
        .chip    = {
            .base    = S5PV210_GPC0(),
            .ngpio    = S5PV210_GPIO_C0_NR,
            .label    = "GPC0",
            .to_irq = s5p_gpiolib_gpioint_to_irq,
        },
    }, {......

四. gpiolib使用方法

4.1. 相关函数gpio_request/gpio_request_one&gpio_free

4.1.1. gpio_request：驱动中要想使用某一个gpio，就必须先调用gpio_request接口来向内核的gpiolib部分申请，得到允许后才可以去使用这个gpio

4.1.2. gpio_request_one：与gpio_request相似，只是在调用该函数同时多了一个设置参数，不同点具体查看内核源码。

4.1.3. gpio_free：对应gpio_request，用来释放申请后用完了的gpio

4.3. 相关函数gpio_request_array&gpio_free_array

4.3.1. gpio_request_array：申请一组gpio。

4.3.2. gpio_free_array：释放一组gpio

4.3. 相关函数gpiochip_is_requested

4.3.1. gpiochip_is_requested：接口用来判断某一个gpio是否已经被申请了

4.4.相关文件目录

目录和文件结构：

mach-s5pv210/gpiolib.c s5pv210_gpiolib_init

mach-s5pv210/include/mach/gpio.h#define S5PV210_GPA0(_nr)(S5PV210_GPIO_A0_START + (_nr))

arch/arm/plat-samsung/gpiolib.c里面是210/6410这种4bit CON寄存器类型的操作方法

arch/arm/plat-samsung/gpio.c里面是24XX这种2bit CON寄存器类型的操作方法

drivers/gpio/gpiolib.c里面是内核开发者提供的gpiolib的驱动框架部分

五. 最终调试效果

[root@musk210 gpio]# cd /sys/class/leds/
[root@musk210 leds]# ls
led1    led2    led3    mmc0::  mmc1::  mmc2::  mmc3::
[root@musk210 leds]# cd led1
[root@musk210 led1]# echo  > brightness
[ 8056.785758] s5pv210_led1_set successful
[root@musk210 led1]# echo  > brightness
[ 8064.545061] s5pv210_led1_set successful
[root@musk210 led1]#

参考《朱老师.课件_5.4.驱动框架入门之LED》

索引文献：https://blog.csdn.net/ultraman_hs/article/details/54952253

索引文献：http://www.cnblogs.com/deng-tao/p/6366905.html