GPIO的驱动模型

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 ) - 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 ))//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 ; 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 ) ptr = gpio_base + 0x10; else if (gpio ) ptr = gpio_base + 0x38; else if (gpio ) ptr = gpio_base + 0x60; else if (gpio ) ptr = gpio_base + 0x88; else if (gpio ) 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 ) { 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 ) { 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 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 ngpio; id++) { gpio_desc[id].chip = chip; gpio_desc[id].flags = !chip->direction_input? (1 ): 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 ; 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, const char *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, const char *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 ) { 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 ) 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 ) { 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 ; 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 ) & __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 ), 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 3static 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_t size,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,const char *src,size_t size,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 (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 ) { 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 ) { 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 ) { 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");

cfm5538

GPIO的驱动模型