一、概述
GPIO是嵌入式系统最简单、最常用的资源了，比如点亮LED，控制蜂鸣器，输出高低电平，检测按键，等等。GPIO分输入和输出，在davinci linux中，有关GPIO的最底层的寄存器驱动，\arch\arm\mach-davinci目录下的gpio.c，这个是寄存器级的驱动，搞过单片机MCU的朋友应该比较熟悉寄存器级的驱动。
GPIO的驱动主要就是读取GPIO口的状态，或者设置GPIO口的状态。就是这么简单，但是为了能够写好的这个驱动，在LINUX上作了一些软件上的分层。为了让其它驱动可以方便的操作到GPIO，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在配置内核的时候，我们必须使用CONFIG_GENERIC_GPIO这个宏来支持GPIO驱动。
GPIO是与硬件体系密切相关的，linux提供一个模型来让驱动统一处理GPIO，即各个板卡都有实现自己的gpio_chip控制模块：request, free,input,output, get,set,irq...然后把控制模块注册到内核中，这时会改变全局gpio数组：gpio_desc[]. 当用户请求gpio时，就会到这个数组中找到，并调用这个GPIO对应的gpio_chip的处理函数。gpio实现为一组可用的 gpio_chip, 由驱动传入对应 gpio的全局序号去 request, dataout,datain, free. 这时会调用gpio_chip中具体的实现。
gpio是一组可控件的脚，由多个寄存器同时控制。通过设置对应的寄存器可以达到设置GPIO口对应状态与功能。数据状态，输入输出方向，清零，中断（那个边沿触发）， 一般是一组（bank）一组的。
寄存器读写函数: __raw_writel() __raw_writeb() __raw_readl() __raw_readb()
二、linux 中GPIO模型的结构
//表示一个gpio口，含对应的gpio_chip.
//对于每一个gpio，都有一个gpio描述符，这个描述符包含了这个gpio所属的控制器即chip和一些标志，label等
struct gpio_desc {
struct gpio_chip *chip;
unsigned long flags;
/* flag symbols are bit numbers */
#define FLAG_REQUESTED 0
#define FLAG_IS_OUT 1
#define FLAG_RESERVED 2
#define FLAG_EXPORT 3 /* protected by sysfs_lock */
#define FLAG_SYSFS 4 /* exported via /sys/class/gpio/control */
#define FLAG_TRIG_FALL 5 /* trigger on falling edge */
#define FLAG_TRIG_RISE 6 /* trigger on rising edge */
#define FLAG_ACTIVE_LOW 7 /* sysfs value has active low */
#define FLAG_OPEN_DRAIN 8 /* Gpio is open drain type */
#define FLAG_OPEN_SOURCE 9 /* Gpio is open source type */
#define ID_SHIFT 16 /* add new flags before this one */
#define GPIO_FLAGS_MASK ((1 << ID_SHIFT) - 1)
#define GPIO_TRIGGER_MASK (BIT(FLAG_TRIG_FALL) | BIT(FLAG_TRIG_RISE))
#ifdef CONFIG_DEBUG_FS
const char *label;
#endif
};
//采用了一个具有ARCH_NR_GPIOS大小的gpio描述符数组。这个描述符数组便代表了系统所有的gpio。
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];//ARCH_NR_GPIOS=144,即系统现在有144个GPIO口
//static struct davinci_gpio_controller chips[DIV_ROUND_UP(DAVINCI_N_GPIO, 32)];//将144个GPIO分成每32个一组
//一组GPIO控制器结构，例如GPIO0和GPIO1是一组(共32个GPIO口)，共用一组寄存器，所以GPIO0和GPIO1荷载一起用chips[0]来控制
///共有144个GPIO，分为4组（GPIO0~GPIO8），每组有2个banks(即GPIO0和GPIO1为1组)，每组最多可以有32个GPIO，每组的控制寄存器空间有10个。
struct davinci_gpio_controller {
struct gpio_chip chip;//每组对应的gpio_chip
int irq_base;//每组对应的中断
spinlock_t lock;//自旋锁
void __iomem *regs;//每组的寄存器地址
void __iomem *set_data;//设置数据寄存器地址
void __iomem *clr_data;//清除数据寄存器地址
void __iomem *in_data;//输入数据寄存器地址
};
//每一个davinci_gpio_controller结构都对应于一个gpio_chip结构，gpio_chip既可看成是davinci_gpio_controller结构的补充
//表示一个gpio controller.通过这个结构抽象化所有的GPIO源，而让板上其它的模块可以用相同的接口调用使用这些GPIO。
struct gpio_chip {
const char *label;
struct device *dev;
struct module *owner;
int (*request)(struct gpio_chip *chip,unsigned offset);//请求gpio
void *free)(struct gpio_chip *chip,unsigned offset);//释放gpio
int (*get_direction)(struct gpio_chip *chip,unsigned offset);
int (*direction_input)(struct gpio_chip *chip,unsigned offset);//配置gpio为输入，返回当前gpio状态
int (*get)(struct gpio_chip *chip,unsigned offset);//获取gpio的状态
int (*direction_output)(struct gpio_chip *chip,unsigned offset, int value);//配置gpio为输出，并设置为value
int (*set_debounce)(struct gpio_chip *chip,unsigned offset, unsigned debounce);//设置消抖动时间，尤其是gpio按键时有用
void (*set)(struct gpio_chip *chip,unsigned offset, int value);//设置gpio为value值
int (*to_irq)(struct gpio_chip *chip,unsigned offset);//把gpio号转换为中断号
void (*dbg_show)(struct seq_file *s,struct gpio_chip *chip);
int base;// 这个gpio控制器的gpio开始编号
u16 ngpio;//这个gpio控制器说控制的gpio数
const char *const *names;
unsigned can_sleep:1;
unsigned exported:1;
#if defined(CONFIG_OF_GPIO)
struct device_node *of_node;
int of_gpio_n_cells;
int (*of_xlate)(struct gpio_chip *gc,const struct of_phandle_args *gpiospec, u32 *flags);
#endif
#ifdef CONFIG_PINCTRL
struct list_head pin_ranges;
#endif
};
//GPIO寄存器结构
struct davinci_gpio_regs {
u32 dir; // gpio方向设置寄存器
u32 out_data; // gpio设置为输出时，表示输出状态(0或1)
u32 set_data; // gpio设置为输出时，用于输出高电平
u32 clr_data; // gpio设置为输出时，用于输出低电平
u32 in_data; // gpio设置为输入时，用于读取输入值
u32 set_rising; // gpio中断上升沿触发设置
u32 clr_rising; // gpio中断上升沿触发清除
u32 set_falling; // gpio中断下降沿触发设置
u32 clr_falling; // gpio中断下降沿触发清除
u32 intstat; // gpio中断状态位，由硬件设置，可读取，写1时清除。
};
struct gpio {
unsigned gpio;//gpio号
unsigned long flags;//gpio标志
const char *label;//gpio名
};
三、GPIO的初始化
1.首先设置GPIO的管脚复用寄存器
static __init void da850_evm_init(void)
{
//.......
ret = davinci_cfg_reg_list(da850_gpio_test_pins);
if (ret)
pr_warning("da850_evm_init: gpio test ping mux setup failed: %d\n", ret);
//.......
}
2.根据板级结构的资源初始化chips数组，此函数在系统初始化时自动调用
static struct davinci_gpio_controller chips[DIV_ROUND_UP(DAVINCI_N_GPIO, 32)];//将144个GPIO分成每32个一组
static int __init davinci_gpio_setup(void)
{
int i, base;
unsigned ngpio;
struct davinci_soc_info *soc_info = &davinci_soc_info;//板级资源结构
struct davinci_gpio_regs *regs;
if (soc_info->gpio_type != GPIO_TYPE_DAVINCI)//判断GPIO类型
return 0;
ngpio = soc_info->gpio_num;//GPIO数量144
if (ngpio == 0){
pr_err("GPIO setup: how many GPIOs?\n");
return -EINVAL;
}
if (WARN_ON(DAVINCI_N_GPIO < ngpio))//DAVINCI_N_GPIO=144
ngpio = DAVINCI_N_GPIO;
gpio_base = ioremap(soc_info->gpio_base, SZ_4K);//将GPIO的寄存器物理基地址（#define DA8XX_GPIO_BASE 0x01e26000）映射到内存中
if (WARN_ON(!gpio_base))
return -ENOMEM;
//共有144个GPIO，分为4组（GPIO0~GPIO8），每组有2个banks(即GPIO0和GPIO1为1组)，每组最多可以有32个GPIO，每组的控制寄存器空间有10个。
//chips[0]--chips[4],base值为0,32,64,96,128,ngpio分别为：32,32,32,32,16
for (i= 0, base = 0; base < ngpio;i++, base += 32){
chips[i].chip.label= "DaVinci";
//设置操作函数
chips[i].chip.direction_input= davinci_direction_in;
chips[i].chip.get= davinci_gpio_get;
chips[i].chip.direction_output= davinci_direction_out;
chips[i].chip.set= davinci_gpio_set;
chips[i].chip.base= base;//每一组开始的GPIO号
//每组控制的GPIO个数，一般为32个
chips[i].chip.ngpio= ngpio - base;
if (chips[i].chip.ngpio > 32)
chips[i].chip.ngpio= 32;
spin_lock_init(&chips[i].lock);
//找到这组GPIO的寄存器地址，初始化chips结构
regs = gpio2regs(base);
chips[i].regs= regs;//设置每组的寄存器
chips[i].set_data= ?s->set_data;
chips[i].clr_data= ?s->clr_data;
chips[i].in_data= ?s->in_data;
gpiochip_add(&chips[i].chip);//注册gpio_chip
}
//chips数组添加到板级资源中
soc_info->gpio_ctlrs = chips;
soc_info->gpio_ctlrs_num = DIV_ROUND_UP(ngpio, 32);
davinci_gpio_irq_setup();//设置GPIO中断
return 0;
}
pure_initcall(davinci_gpio_setup);//linux初始化时会自动调用
static struct davinci_gpio_regs __iomem __init *gpio2regs(unsigned gpio)
{
void __iomem *ptr;
//根据GPIO的基地址累加，其中基地址(gpio_base+0)是REVID(Revision ID Register)寄存器
//(gpio_base+8)是BINTEN(GPIO Interrupt Per-Bank Enable Register)寄存器
//所以第一组寄存器从基地址+0x10开始
if (gpio < 32 * 1)
ptr = gpio_base + 0x10;
else if (gpio < 32 * 2)
ptr = gpio_base + 0x38;
else if (gpio < 32 * 3)
ptr = gpio_base + 0x60;
else if (gpio < 32 * 4)
ptr = gpio_base + 0x88;
else if (gpio < 32 * 5)
ptr = gpio_base + 0xb0;
else
ptr = NULL;
return ptr;
}
int gpiochip_add(struct gpio_chip *chip)
{
unsigned long flags;
int status = 0;
unsigned id;
int base = chip->base;
//检测gpio的有效性，判断这组GPIO的起始号是否在有效范围内
if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))&& base >= 0){
status = -EINVAL;
goto fail;
}
spin_lock_irqsave(&gpio_lock, flags);
//如果这组GPIO的起始号小于0，则动态的分配gpio的开始索引。
if (base < 0){
base = gpiochip_find_base(chip->ngpio);//这个函数在gpiolib.c中，在gpio_desc[]中分配chip->ngpio个空间(从最后往前分配)，返回第一个index
if (base < 0){
status = base;
goto unlock;
}
chip->base = base;
}
//确保这些分配的gpio号没有被其他chip占用
for (id = base; id < base + chip->ngpio; id++){
if (gpio_desc[id].chip != NULL){
status = -EBUSY;
break;
}
}
//填充gpio_desc，将该组内的每个GPIO口的gpio_desc结构和该组的控制结构chip联系起来
if (status == 0){
for (id = base; id < base + chip->ngpio; id++){
gpio_desc[id].chip = chip;
gpio_desc[id].flags = !chip->direction_input? (1 << FLAG_IS_OUT): 0;//设置GPIO口标志
}
}
of_gpiochip_add(chip);
unlock:
spin_unlock_irqrestore(&gpio_lock, flags);
if (status)
goto fail;
status = gpiochip_export(chip);//与sysfs文件系统有关，这里不关心
if (status)
goto fail;
return 0;
fail:
/* failures here can mean systems won't boot... */
pr_err("gpiochip_add: gpios %d..%d (%s) failed to register\n",chip->base, chip->base + chip->ngpio - 1,chip->label ? : "generic");
return status;
}
四.gpio的申请
//所谓申请就是检测GPIO描述符desc->flags的FLAG_REQUESTED标志，已申请的话该标志是1，否则是0
//往往多个gpio作为一个数组来进行申请
int gpio_request_array(struct gpio *array, size_t num)
{
int i, err;
for (i= 0; i < num; i++, array++){//遍历数组中的每一个GPIO，gpio是GPIO号，flags是输入输出标志等，label是其取一个名字
err = gpio_request_one(array->gpio, array->flags, array->label);
if (err)
goto err_free;
}
return 0;
err_free:
while (i--)
gpio_free((--array)->gpio);
return err;
}
int gpio_request_one(unsigned gpio, unsigned long flags, constchar *label)
{
int err;
//gpio则为你要申请的哪一个管脚，label则是为其取一个名字。
err = gpio_request(gpio,label);
if (err)
return err;
if (flags & GPIOF_DIR_IN)//GPIO标志是输入
err = gpio_direction_input(gpio);//设置管脚为输入
else//GPIO标志是输出
err = gpio_direction_output(gpio,(flags & GPIOF_INIT_HIGH) ? 1: 0);//根据标志确定输出1还是0
if (err)
gpio_free(gpio);
return err;
}
int gpio_request(unsigned gpio, constchar *label)
{
struct gpio_desc *desc;
struct gpio_chip *chip;
int status = -EINVAL;
unsigned long flags;
//屏蔽中断
spin_lock_irqsave(&gpio_lock, flags);
if (!gpio_is_valid(gpio))//判断是否有效，也就是参数的取值范围判断
goto done;
//根据GPIO号找到对应的GPIO描述符结构
desc = &gpio_desc[gpio];
chip = desc->chip;//找到该GPIO所在的组控制器
if (chip == NULL)
goto done;
//计数加1
if (!try_module_get(chip->owner))
goto done;
//这里测试并设置flags的第FLAG_REQUESTED位，如果没有被申请就返回该位的原值0
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags)== 0){
desc_set_label(desc,label ? : "?");//设置GPIO描述符结构desc的label字段
status = 0;
} else {
status = -EBUSY;
module_put(chip->owner);
goto done;
}
if (chip->request){/* chip->request may sleep */
spin_unlock_irqrestore(&gpio_lock, flags);
status = chip->request(chip, gpio - chip->base);
spin_lock_irqsave(&gpio_lock, flags);
if (status < 0){
desc_set_label(desc, NULL);
module_put(chip->owner);
clear_bit(FLAG_REQUESTED, &desc->flags);
}
}
done:
if (status)
pr_debug("gpio_request: gpio-%d (%s) status %d\n",gpio,label ? : "?", status);
spin_unlock_irqrestore(&gpio_lock, flags);
return status;
}
五.GPIO的操作
1.设置GPIO为输出或输入
int gpio_direction_input(unsigned gpio)
{
unsigned long flags;
struct gpio_chip *chip;
struct gpio_desc *desc = &gpio_desc[gpio];
int status = -EINVAL;
spin_lock_irqsave(&gpio_lock, flags);
//判断GPIO号是否有效
if (!gpio_is_valid(gpio))
goto fail;
//找到GPIO对应的gpio_chip结构
chip = desc->chip;
if (!chip || !chip->get || !chip->direction_input)
goto fail;
//确保此GPIO是在此组内，chip->base是此组GPIO的起始号，chip->ngpio是此组GPIO的个数
gpio -= chip->base;
if (gpio >= chip->ngpio)
goto fail;
//确保GPIO已申请
status = gpio_ensure_requested(desc, gpio);
if (status < 0)
goto fail;
//到这里可以确保GPIO是有效的
spin_unlock_irqrestore(&gpio_lock, flags);
might_sleep_if(chip->can_sleep);
//status=0
if (status){
status = chip->request(chip, gpio);
if (status < 0){
pr_debug("GPIO-%d: chip request fail, %d\n",chip->base + gpio, status);
goto lose;
}
}
//调用底层的已经设置过的操作，这里即davinci_direction_in
status = chip->direction_input(chip, gpio);
if (status == 0)//返回成功
clear_bit(FLAG_IS_OUT, &desc->flags);//清除输出标志
lose:
return status;
fail:
spin_unlock_irqrestore(&gpio_lock, flags);
if (status)
pr_debug("%s: gpio-%d status %d\n",__func__, gpio, status);
return status;
}
int gpio_direction_output(unsigned gpio, int value)
{
//.........GPIO的检查，同上函数
//调用底层的已经设置过的操作，这里即davinci_direction_out
status = chip->direction_output(chip, gpio, value);
if (status == 0)//返回成功
set_bit(FLAG_IS_OUT, &desc->flags);//设置输出标志
lose:
return status;
fail:
spin_unlock_irqrestore(&gpio_lock, flags);
if (status)
pr_debug("%s: gpio-%d status %d\n",__func__, gpio, status);
return status;
}
//根据前边对gpio_chip结构的初始化，会调用\arch\arm\mach-davinci\gpio.c里的函数
static int davinci_direction_in(struct gpio_chip *chip, unsigned offset)
{
return __davinci_direction(chip, offset, false, 0);
}
static int davinci_direction_out(struct gpio_chip *chip, unsigned offset, int value)
{
return __davinci_direction(chip, offset, true, value);
}
static inline int __davinci_direction(struct gpio_chip *chip,unsigned offset, bool out, int value)
{
struct davinci_gpio_controller *d = chip2controller(chip);
struct davinci_gpio_regs __iomem *g = d->regs;//找到此组GPIO的控制寄存器地址
unsigned long flags;
u32 temp;
u32 mask = 1 << offset;
spin_lock_irqsave(&d->lock, flags);
temp = __raw_readl(&g->dir);//读出当前寄存器的输入输出方向
if (out){//为1设置输出
temp &= ~mask;
__raw_writel(mask, value ? &g->set_data: &g->clr_data);//确定是用于输出高电平还是输出低电平
}
else {//为0设置为输入
temp |= mask;
}
__raw_writel(temp, &g->dir);//写入方向寄存器
spin_unlock_irqrestore(&d->lock, flags);
return 0;
}
2.获取gpio的状态
int __gpio_get_value(unsigned gpio)
{
struct gpio_chip *chip;
chip = gpio_to_chip(gpio);
WARN_ON(chip->can_sleep);
return chip->get ? chip->get(chip, gpio - chip->base): 0;//调用davinci_gpio_get
}
static int davinci_gpio_get(struct gpio_chip *chip, unsigned offset)
{
struct davinci_gpio_controller *d = chip2controller(chip);
struct davinci_gpio_regs __iomem *g = d->regs;
return (1 << offset) & __raw_readl(&g->in_data);
}
3.设置GPIO的值
void __gpio_set_value(unsigned gpio, int value)
{
struct gpio_chip *chip;
chip = gpio_to_chip(gpio);
WARN_ON(chip->can_sleep);
chip->set(chip, gpio - chip->base, value);//调用davinci_gpio_set
}
static void davinci_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
{
struct davinci_gpio_controller *d = chip2controller(chip);
struct davinci_gpio_regs __iomem *g = d->regs;
__raw_writel((1 << offset), value ? &g->set_data: &g->clr_data);
}
六、GPIO驱动编写
1.首先要申请GPIO口
2.注册设备
3.创建GPIO的sysfs相关文件
#define GPIO_MAJOR 199 // major device NO.
#define GPIO_MINOR 0 // minor device NO.
#define DEVICE_NAME "omapl138_gpios" /*定义设备驱动的名字，或设备节点名称*/
#define SET_OUTPUT_LOW 0
#define SET_OUTPUT_HIGH 1
#define GET_VALUE 2
#define SET_INPUT 3
static struct class *gpio_class;
static struct gpio gpio_array[] =
{
/*{ GPIO_TO_PIN(0, 0), GPIOF_OUT_INIT_LOW, "RTU_WDI_SIGNAL" },will request fail*/
{ GPIO_TO_PIN(0, 1), GPIOF_OUT_INIT_HIGH,"RTU_PLC_BAK_IO1"},
{ GPIO_TO_PIN(0, 2), GPIOF_OUT_INIT_LOW, "RTU_CHG_EN" },
{ GPIO_TO_PIN(0, 3), GPIOF_IN, "RTU_CHG_PG"},
{ GPIO_TO_PIN(0, 5), GPIOF_IN, "RTU_USB_OC_OUT"},
{ GPIO_TO_PIN(0, 6), GPIOF_OUT_INIT_LOW, "RTU_RUN_IND_LED" },
{ GPIO_TO_PIN(1, 10), GPIOF_IN, "RTU_TSC_BUSY"},
{ GPIO_TO_PIN(1, 11), GPIOF_IN, "RTU_PENIRQn"},
{ GPIO_TO_PIN(1, 12), GPIOF_OUT_INIT_LOW,"RTU_uP_Q26x_RESET" },
{ GPIO_TO_PIN(1, 13), GPIOF_OUT_INIT_HIGH,"RTU_uP_GPRS_PWR_EN" },
{ GPIO_TO_PIN(1, 14), GPIOF_OUT_INIT_HIGH,"RTU_uP_Q26x_ON/OFF" },
{ GPIO_TO_PIN(2, 1), GPIOF_OUT_INIT_LOW,"RTU_PLC_Reset" },
{ GPIO_TO_PIN(2, 2), GPIOF_OUT_INIT_LOW,"RTU_PLC_T_Reg" },
{ GPIO_TO_PIN(2, 4), GPIOF_OUT_INIT_LOW,"RTU_PLC_BAK_IO2" },
{ GPIO_TO_PIN(2, 5), GPIOF_OUT_INIT_LOW,"RTU_RS485_RE" },
{ GPIO_TO_PIN(2, 15), GPIOF_OUT_INIT_HIGH,"RTU_CHPWR_CS" },
{ GPIO_TO_PIN(3, 9), GPIOF_OUT_INIT_HIGH,"RTU_RS485_DE" },
{ GPIO_TO_PIN(6, 1), GPIOF_OUT_INIT_HIGH,"RTU_uP_VPIF_CLKO3" },
{ GPIO_TO_PIN(6, 9), GPIOF_IN, "RTU_KEY_IN2"},
{ GPIO_TO_PIN(6, 11), GPIOF_IN, "RTU_ALARM_IN5"},
{ GPIO_TO_PIN(6, 15), GPIOF_OUT_INIT_HIGH,"RTU_uP_RESETOUTn"},
};
static int gpio_open(struct inode *inode,struct file *file)
{
printk(KERN_WARNING"gpio open success!\n");
return 0;
}
static int gpio_release(struct inode *inode, struct file *filp)
{
printk (KERN_ALERT "Device gpio released\n");
return 0;
}
static int gpio_read(struct file*f,char *dst,size_tsize,loff_t*offset)
{
unsigned char num;
__copy_to_user(&num,dst,1);
#ifdef DEBUG
printk("__copy_to_user:%d\n",num);
#endif
return 0;
}
static int gpio_write(struct file*f,constchar *src,size_tsize,loff_t *offset)
{
unsigned char num;
__copy_from_user(&num,src,1);
#ifdef DEBUG
printk("__copy_from_user:%d\n",num);
#endif
return 0;
}
static long gpio_ioctl(struct file *file,unsigned int cmd,unsigned long gpio)
{
int i;
unsigned long gpio_num = (gpio/100)*16+gpio%100;
for (i= 0; i < ARRAY_SIZE(gpio_array);i++){
if(gpio_array[i].gpio== gpio_num)
goto valid_gpio;
}
return -1;
valid_gpio:
switch(cmd)//cmd表示应用程序传入的 GPIO 动作
{
case SET_OUTPUT_LOW://0
{
gpio_direction_output(gpio_num, 0);
break;
}
case SET_OUTPUT_HIGH://1
{
gpio_direction_output(gpio_num, 1);
break;
}
case GET_VALUE://2
{
return gpio_get_value(gpio_num);
}
case SET_INPUT://3
{
gpio_direction_input(gpio_num);
break;
}
default:
{
printk(KERN_EMERG "GPIO command mistake!!!\n");
break;
}
}
return 0;
}
static const struct file_operations gpio_fops=
{
.owner = THIS_MODULE,
.open = gpio_open,
.release = gpio_release,
.read = gpio_read,
.write = gpio_write,
.unlocked_ioctl = gpio_ioctl,
};
static int __init gpio_init(void)/*内核初始化会调用该函数*/
{
int ret;
ret = gpio_request_array(gpio_array, ARRAY_SIZE(gpio_array));
if (ret < 0)
{
printk(KERN_EMERG "GPIO request failed\n");
goto request_failed;
}
dev_t my_dev_no;
struct cdev *gpio_cdev;
gpio_cdev = cdev_alloc();
if(gpio_cdev == NULL)
{
printk(KERN_EMERG "Cannot alloc cdev\n");
goto request_failed;
}
cdev_init(gpio_cdev,&gpio_fops);
gpio_cdev->owner=THIS_MODULE;
int result=alloc_chrdev_region(&my_dev_no,0,1,DEVICE_NAME);
if(result < 0)
{
printk(KERN_EMERG "alloc_chrdev_region failed\n");
goto request_failed;
}
ret=cdev_add(gpio_cdev,my_dev_no,1);
ret = register_chrdev(GPIO_MAJOR, DEVICE_NAME, &gpio_fops);//驱动字符设备
if(ret < 0)
{
printk(KERN_EMERG "GPIO register failed\n");
goto request_failed;
}
//在sysfs文件系统下创建一个类
gpio_class = class_create(THIS_MODULE, DEVICE_NAME);
//device_create-->device_create_vargs-->device_register创建相应的sysfs文件(如dev文件)，用于udev根据sysfs文件系统下的dev文件创建设备节点
device_create(gpio_class, NULL, MKDEV(GPIO_MAJOR, GPIO_MINOR), NULL, DEVICE_NAME);
return ret;
request_failed:
gpio_free_array(gpio_array, ARRAY_SIZE(gpio_array));
return ret;
}
static void __exit gpio_exit(void)
{
device_destroy(gpio_class, MKDEV(GPIO_MAJOR, GPIO_MINOR));
class_unregister(gpio_class);
class_destroy(gpio_class);
unregister_chrdev(GPIO_MAJOR, DEVICE_NAME);
}
module_init(gpio_init);
module_exit(gpio_exit);
MODULE_LICENSE("GPL");
MODULE_VERSION ("v2.0");
MODULE_AUTHOR("wbl <>");
MODULE_DESCRIPTION("OMAPL138 GPIO driver");GPIO的驱动模型
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