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GPIO的驱动模型

分类： LINUX

2014-08-29 23:38:42

原文地址：GPIO的驱动模型 作者：wangbaolin719


  1. 一、概述
  2. 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。

  4. 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。

  6. 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。
  7. 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。
  8. 寄存器读写函数: __raw_writel() __raw_writeb() __raw_readl() __raw_readb()

  10. 二、linux 中GPIO模型的结构
  11. //表示一个gpio口，含对应的gpio_chip.
  12. //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
  13. struct gpio_desc {
  14.     struct gpio_chip    *chip;
  15.     unsigned long    flags;
  16.     /* flag symbols are bit numbers */
  17.     #define FLAG_REQUESTED 0
  18.     #define FLAG_IS_OUT 1
  19.     #define FLAG_RESERVED 2
  20.     #define FLAG_EXPORT 3 /* protected by sysfs_lock */
  21.     #define FLAG_SYSFS 4 /* exported via /sys/class/gpio/control */
  22.     #define FLAG_TRIG_FALL 5 /* trigger on falling edge */
  23.     #define FLAG_TRIG_RISE 6 /* trigger on rising edge */
  24.     #define FLAG_ACTIVE_LOW 7 /* sysfs value has active low */
  25.     #define FLAG_OPEN_DRAIN 8 /* Gpio is open drain type */
  26.     #define FLAG_OPEN_SOURCE 9 /* Gpio is open source type */
  27.     
  28.     #define ID_SHIFT 16 /* add new flags before this one */
  29.     #define GPIO_FLAGS_MASK ((1 << ID_SHIFT) - 1)
  30.     #define GPIO_TRIGGER_MASK (BIT(FLAG_TRIG_FALL) | BIT(FLAG_TRIG_RISE))
  31.  
  32. #ifdef CONFIG_DEBUG_FS
  33.     const char    *label;
  34. #endif
  35. };
  36. //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。
  37. static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];//ARCH_NR_GPIOS=144,即系统现在有144个GPIO口

  39. //static struct davinci_gpio_controller chips[DIV_ROUND_UP(DAVINCI_N_GPIO, 32)];//将144个GPIO分成每32个一组
  40. //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
  41. ///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。
  42. struct davinci_gpio_controller {
  43.     struct gpio_chip    chip;//每组对应的gpio_chip
  44.     int            irq_base;//每组对应的中断
  45.     spinlock_t        lock;//自旋锁
  46.     void __iomem        *regs;//每组的寄存器地址
  47.     void __iomem        *set_data;//设置数据寄存器地址
  48.     void __iomem        *clr_data;//清除数据寄存器地址
  49.     void __iomem        *in_data;//输入数据寄存器地址
  50. };

  52. //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
  53. //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。
  54. struct gpio_chip {
  55.     const char    *label;
  56.     struct device    *dev;
  57.     struct module    *owner;
  58.     int    (*request)(struct gpio_chip *chip,unsigned offset);//请求gpio
  59.     void    *free)(struct gpio_chip *chip,unsigned offset);//释放gpio
  60.     int    (*get_direction)(struct gpio_chip *chip,unsigned offset);
  61.     int    (*direction_input)(struct gpio_chip *chip,unsigned offset);//配置gpio为输入，返回当前gpio状态
  62.     int    (*get)(struct gpio_chip *chip,unsigned offset);//获取gpio的状态
  63.     int    (*direction_output)(struct gpio_chip *chip,unsigned offset, int value);//配置gpio为输出，并设置为value
  64.     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
  65.     void    (*set)(struct gpio_chip *chip,unsigned offset, int value);//设置gpio为value值
  66.     int    (*to_irq)(struct gpio_chip *chip,unsigned offset);//把gpio号转换为中断号
  67.     void    (*dbg_show)(struct seq_file *s,struct gpio_chip *chip);
  68.     int    base;// 这个gpio控制器的gpio开始编号
  69.     u16    ngpio;//这个gpio控制器说控制的gpio数
  70.     const char    *const *names;
  71.     unsigned    can_sleep:1;
  72.     unsigned    exported:1;
  73.  
  74. #if defined(CONFIG_OF_GPIO)
  75.     struct device_node *of_node;
  76.     int of_gpio_n_cells;
  77.     int (*of_xlate)(struct gpio_chip *gc,const struct of_phandle_args *gpiospec, u32 *flags);
  78. #endif
  79. #ifdef CONFIG_PINCTRL
  80.     struct list_head pin_ranges;
  81. #endif
  82. };

  84. //GPIO寄存器结构
  85. struct davinci_gpio_regs {
  86.     u32 dir; // gpio方向设置寄存器
  87.     u32 out_data; // gpio设置为输出时，表示输出状态(0或1)
  88.     u32 set_data; // gpio设置为输出时，用于输出高电平
  89.     u32 clr_data; // gpio设置为输出时，用于输出低电平
  90.     u32 in_data; // gpio设置为输入时，用于读取输入值
  91.     u32 set_rising; // gpio中断上升沿触发设置
  92.     u32 clr_rising; // gpio中断上升沿触发清除
  93.     u32 set_falling; // gpio中断下降沿触发设置
  94.     u32 clr_falling; // gpio中断下降沿触发清除
  95.     u32 intstat; // gpio中断状态位，由硬件设置，可读取，写1时清除。
  96. };

  98. struct gpio {
  99.     unsigned gpio;//gpio号
  100.     unsigned long flags;//gpio标志
  101.     const char *label;//gpio名
  102. };

  104. 三、GPIO的初始化
  105. 1.首先设置GPIO的管脚复用寄存器
  106. static __init void da850_evm_init(void)
  107. {
  108.     //.......
  109.     ret = davinci_cfg_reg_list(da850_gpio_test_pins);
  110.     if (ret)
  111.         pr_warning("da850_evm_init: gpio test ping mux setup failed: %d\n", ret);
  112.     //.......
  113. }

  115. 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
  116. static struct davinci_gpio_controller chips[DIV_ROUND_UP(DAVINCI_N_GPIO, 32)];//将144个GPIO分成每32个一组
  117. static int __init davinci_gpio_setup(void)
  118. {
  119.     int i, base;
  120.     unsigned ngpio;
  121.     struct davinci_soc_info *soc_info = &davinci_soc_info;//板级资源结构
  122.     struct davinci_gpio_regs *regs;

  124.     if (soc_info->gpio_type != GPIO_TYPE_DAVINCI)//判断GPIO类型
  125.         return 0;

  127.     ngpio = soc_info->gpio_num;//GPIO数量144
  128.     if (ngpio == 0) {
  129.         pr_err("GPIO setup: how many GPIOs?\n");
  130.         return -EINVAL;
  131.     }

  133.     if (WARN_ON(DAVINCI_N_GPIO < ngpio))//DAVINCI_N_GPIO=144
  134.         ngpio = DAVINCI_N_GPIO;

  136.     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
  137.     if (WARN_ON(!gpio_base))
  138.         return -ENOMEM;
  139.     
  140.     //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。
  141.     //chips[0]--chips[4],base值为0,32,64,96,128,ngpio分别为：32,32,32,32,16
  142.     for (i = 0, base = 0; base < ngpio; i++, base += 32) {
  143.         chips[i].chip.label = "DaVinci";
  144.         //设置操作函数
  145.         chips[i].chip.direction_input = davinci_direction_in;
  146.         chips[i].chip.get = davinci_gpio_get;
  147.         chips[i].chip.direction_output = davinci_direction_out;
  148.         chips[i].chip.set = davinci_gpio_set;

  150.         chips[i].chip.base = base;//每一组开始的GPIO号
  151.         //每组控制的GPIO个数，一般为32个
  152.         chips[i].chip.ngpio = ngpio - base;
  153.         if (chips[i].chip.ngpio > 32)
  154.             chips[i].chip.ngpio = 32;

  156.         spin_lock_init(&chips[i].lock);
  157.         //找到这组GPIO的寄存器地址，初始化chips结构
  158.         regs = gpio2regs(base);
  159.         chips[i].regs = regs;//设置每组的寄存器
  160.         chips[i].set_data = ?s->set_data;
  161.         chips[i].clr_data = ?s->clr_data;
  162.         chips[i].in_data = ?s->in_data;
  163.         
  164.         gpiochip_add(&chips[i].chip);//注册gpio_chip
  165.     }
  166.     //chips数组添加到板级资源中
  167.     soc_info->gpio_ctlrs = chips;
  168.     soc_info->gpio_ctlrs_num = DIV_ROUND_UP(ngpio, 32);

  170.     davinci_gpio_irq_setup();//设置GPIO中断
  171.     return 0;
  172. }
  173. pure_initcall(davinci_gpio_setup);//linux初始化时会自动调用

  175. static struct davinci_gpio_regs __iomem __init *gpio2regs(unsigned gpio)
  176. {
  177.     void __iomem *ptr;
  178.     
  179.     //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
  180.     //(gpio_base+8)是BINTEN (GPIO Interrupt Per-Bank Enable Register)寄存器
  181.     //所以第一组寄存器从基地址+0x10开始
  182.     if (gpio < 32 * 1)
  183.         ptr = gpio_base + 0x10;
  184.     else if (gpio < 32 * 2)
  185.         ptr = gpio_base + 0x38;
  186.     else if (gpio < 32 * 3)
  187.         ptr = gpio_base + 0x60;
  188.     else if (gpio < 32 * 4)
  189.         ptr = gpio_base + 0x88;
  190.     else if (gpio < 32 * 5)
  191.         ptr = gpio_base + 0xb0;
  192.     else
  193.         ptr = NULL;
  194.     return ptr;
  195. }

  197. int gpiochip_add(struct gpio_chip *chip)
  198. {
  199.     unsigned long    flags;
  200.     int        status = 0;
  201.     unsigned    id;
  202.     int        base = chip->base;
  203.     
  204.     //检测gpio的有效性，判断这组GPIO的起始号是否在有效范围内
  205.     if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))&& base >= 0) {
  206.         status = -EINVAL;
  207.         goto fail;
  208.     }

  210.     spin_lock_irqsave(&gpio_lock, flags);
  211.     
  212.     //如果这组GPIO的起始号小于0，则动态的分配gpio的开始索引。
  213.     if (base < 0) {
  214.         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
  215.         if (base < 0) {
  216.             status = base;
  217.             goto unlock;
  218.         }
  219.         chip->base = base;
  220.     }

  222.     //确保这些分配的gpio号没有被其他chip占用
  223.     for (id = base; id < base + chip->ngpio; id++) {
  224.         if (gpio_desc[id].chip != NULL) {
  225.             status = -EBUSY;
  226.             break;
  227.         }
  228.     }
  229.     //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
  230.     if (status == 0) {
  231.         for (id = base; id < base + chip->ngpio; id++) {
  232.             gpio_desc[id].chip = chip;
  233.             gpio_desc[id].flags = !chip->direction_input? (1 << FLAG_IS_OUT): 0;//设置GPIO口标志
  234.         }
  235.     }
  236.     of_gpiochip_add(chip);

  238. unlock:
  239.     spin_unlock_irqrestore(&gpio_lock, flags);

  241.     if (status)
  242.         goto fail;

  244.     status = gpiochip_export(chip);//与sysfs文件系统有关，这里不关心
  245.     if (status)
  246.         goto fail;

  248.     return 0;
  249. fail:
  250.     /* failures here can mean systems won't boot... */
  251.     pr_err("gpiochip_add: gpios %d..%d (%s) failed to register\n",chip->base, chip->base + chip->ngpio - 1,chip->label ? : "generic");
  252.     return status;
  253. }

  255. 四.gpio的申请
  256. //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
  257. //往往多个gpio作为一个数组来进行申请
  258. int gpio_request_array(struct gpio *array, size_t num)
  259. {
  260.     int i, err;

  262.     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
  263.         err = gpio_request_one(array->gpio, array->flags, array->label);
  264.         if (err)
  265.             goto err_free;
  266.     }
  267.     return 0;

  269. err_free:
  270.     while (i--)
  271.         gpio_free((--array)->gpio);
  272.     return err;
  273. }

  275. int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
  276. {
  277.     int err;
  278.     
  279.     //gpio则为你要申请的哪一个管脚，label则是为其取一个名字。
  280.     err = gpio_request(gpio, label);
  281.     if (err)
  282.         return err;

  284.     if (flags & GPIOF_DIR_IN)//GPIO标志是输入
  285.         err = gpio_direction_input(gpio);//设置管脚为输入
  286.     else//GPIO标志是输出
  287.         err = gpio_direction_output(gpio,(flags & GPIOF_INIT_HIGH) ? 1 : 0);//根据标志确定输出1还是0

  289.     if (err)
  290.         gpio_free(gpio);

  292.     return err;
  293. }

  295. int gpio_request(unsigned gpio, const char *label)
  296. {
  297.     struct gpio_desc    *desc;
  298.     struct gpio_chip    *chip;
  299.     int            status = -EINVAL;
  300.     unsigned long        flags;
  301.     //屏蔽中断
  302.     spin_lock_irqsave(&gpio_lock, flags);

  304.     if (!gpio_is_valid(gpio))//判断是否有效，也就是参数的取值范围判断
  305.         goto done;
  306.         
  307.     //根据GPIO号找到对应的GPIO描述符结构
  308.     desc = &gpio_desc[gpio];
  309.     chip = desc->chip;//找到该GPIO所在的组控制器
  310.     if (chip == NULL)
  311.         goto done;
  312.         
  313.     //计数加1
  314.     if (!try_module_get(chip->owner))
  315.         goto done;

  317.     //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
  318.     if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
  319.         desc_set_label(desc, label ? : "?");//设置GPIO描述符结构desc的label字段
  320.         status = 0;
  321.     } else {
  322.         status = -EBUSY;
  323.         module_put(chip->owner);
  324.         goto done;
  325.     }

  327.     if (chip->request) {/* chip->request may sleep */
  328.         spin_unlock_irqrestore(&gpio_lock, flags);
  329.         status = chip->request(chip, gpio - chip->base);
  330.         spin_lock_irqsave(&gpio_lock, flags);

  332.         if (status < 0) {
  333.             desc_set_label(desc, NULL);
  334.             module_put(chip->owner);
  335.             clear_bit(FLAG_REQUESTED, &desc->flags);
  336.         }
  337.     }

  339. done:
  340.     if (status)
  341.         pr_debug("gpio_request: gpio-%d (%s) status %d\n",gpio, label ? : "?", status);
  342.     spin_unlock_irqrestore(&gpio_lock, flags);
  343.     return status;
  344. }

  346. 五.GPIO的操作
  347. 1.设置GPIO为输出或输入
  348. int gpio_direction_input(unsigned gpio)
  349. {
  350.     unsigned long        flags;
  351.     struct gpio_chip    *chip;
  352.     struct gpio_desc    *desc = &gpio_desc[gpio];
  353.     int            status = -EINVAL;

  355.     spin_lock_irqsave(&gpio_lock, flags);
  356.     
  357.     //判断GPIO号是否有效
  358.     if (!gpio_is_valid(gpio))
  359.         goto fail;
  360.     //找到GPIO对应的gpio_chip结构
  361.     chip = desc->chip;
  362.     if (!chip || !chip->get || !chip->direction_input)
  363.         goto fail;
  364.     
  365.     //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
  366.     gpio -= chip->base;
  367.     if (gpio >= chip->ngpio)
  368.         goto fail;
  369.         
  370.     //确保GPIO已申请
  371.     status = gpio_ensure_requested(desc, gpio);
  372.     if (status < 0)
  373.         goto fail;

  375.     //到这里可以确保GPIO是有效的
  376.     spin_unlock_irqrestore(&gpio_lock, flags);

  378.     might_sleep_if(chip->can_sleep);
  379.     //status=0
  380.     if (status) {
  381.         status = chip->request(chip, gpio);
  382.         if (status < 0) {
  383.             pr_debug("GPIO-%d: chip request fail, %d\n",chip->base + gpio, status);
  384.             goto lose;
  385.         }
  386.     }
  387.     //调用底层的已经设置过的操作，这里即davinci_direction_in
  388.     status = chip->direction_input(chip, gpio);
  389.     if (status == 0)//返回成功
  390.         clear_bit(FLAG_IS_OUT, &desc->flags);//清除输出标志
  391. lose:
  392.     return status;
  393. fail:
  394.     spin_unlock_irqrestore(&gpio_lock, flags);
  395.     if (status)
  396.         pr_debug("%s: gpio-%d status %d\n",__func__, gpio, status);
  397.     return status;
  398. }

  400. int gpio_direction_output(unsigned gpio, int value)
  401. {
  402.     //.........GPIO的检查，同上函数
  403.     
  404.     //调用底层的已经设置过的操作，这里即davinci_direction_out
  405.     status = chip->direction_output(chip, gpio, value);
  406.     if (status == 0)//返回成功
  407.         set_bit(FLAG_IS_OUT, &desc->flags);//设置输出标志
  408. lose:
  409.     return status;
  410. fail:
  411.     spin_unlock_irqrestore(&gpio_lock, flags);
  412.     if (status)
  413.         pr_debug("%s: gpio-%d status %d\n",__func__, gpio, status);
  414.     return status;
  415. }

  417. //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
  418. static int davinci_direction_in(struct gpio_chip *chip, unsigned offset)
  419. {
  420.     return __davinci_direction(chip, offset, false, 0);
  421. }

  423. static int davinci_direction_out(struct gpio_chip *chip, unsigned offset, int value)
  424. {
  425.     return __davinci_direction(chip, offset, true, value);
  426. }

  428. static inline int __davinci_direction(struct gpio_chip *chip,unsigned offset, bool out, int value)
  429. {
  430.     struct davinci_gpio_controller *d = chip2controller(chip);
  431.     struct davinci_gpio_regs __iomem *g = d->regs;//找到此组GPIO的控制寄存器地址
  432.     unsigned long flags;
  433.     u32 temp;
  434.     u32 mask = 1 << offset;

  436.     spin_lock_irqsave(&d->lock, flags);
  437.     temp = __raw_readl(&g->dir);//读出当前寄存器的输入输出方向
  438.     
  439.     if (out) {//为1设置输出
  440.         temp &= ~mask;
  441.         __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
  442.     }
  443.     else {//为0设置为输入
  444.         temp |= mask;
  445.     }
  446.     __raw_writel(temp, &g->dir);//写入方向寄存器
  447.     spin_unlock_irqrestore(&d->lock, flags);

  449.     return 0;
  450. }

  452. 2.获取gpio的状态
  453. int __gpio_get_value(unsigned gpio)
  454. {
  455.     struct gpio_chip    *chip;

  457.     chip = gpio_to_chip(gpio);
  458.     WARN_ON(chip->can_sleep);
  459.     return chip->get ? chip->get(chip, gpio - chip->base) : 0;//调用davinci_gpio_get
  460. }

  462. static int davinci_gpio_get(struct gpio_chip *chip, unsigned offset)
  463. {
  464.     struct davinci_gpio_controller *d = chip2controller(chip);
  465.     struct davinci_gpio_regs __iomem *g = d->regs;

  467.     return (1 << offset) & __raw_readl(&g->in_data);
  468. }

  470. 3.设置GPIO的值
  471. void __gpio_set_value(unsigned gpio, int value)
  472. {
  473.     struct gpio_chip    *chip;

  475.     chip = gpio_to_chip(gpio);
  476.     WARN_ON(chip->can_sleep);
  477.     chip->set(chip, gpio - chip->base, value);//调用davinci_gpio_set
  478. }

  480. static void davinci_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
  481. {
  482.     struct davinci_gpio_controller *d = chip2controller(chip);
  483.     struct davinci_gpio_regs __iomem *g = d->regs;

  485.     __raw_writel((1 << offset), value ? &g->set_data : &g->clr_data);
  486. }

  488. 六、GPIO驱动编写
  489. 1.首先要申请GPIO口
  490. 2.注册设备
  491. 3.创建GPIO的sysfs相关文件
  492. #define GPIO_MAJOR 199         // major device NO.
  493. #define GPIO_MINOR 0         // minor device NO.
  494. #define DEVICE_NAME "omapl138_gpios" /*定义设备驱动的名字，或设备节点名称*/

  496. #define SET_OUTPUT_LOW 0
  497. #define SET_OUTPUT_HIGH 1
  498. #define GET_VALUE 2
  499. #define SET_INPUT 3

  501. static struct class *gpio_class;
  502. static struct gpio gpio_array[] =
  503. {
  504.     /*{ GPIO_TO_PIN(0, 0), GPIOF_OUT_INIT_LOW,     "RTU_WDI_SIGNAL" },will request fail*/
  505.     { GPIO_TO_PIN(0, 1), GPIOF_OUT_INIT_HIGH, "RTU_PLC_BAK_IO1"},
  506.     { GPIO_TO_PIN(0, 2), GPIOF_OUT_INIT_LOW,     "RTU_CHG_EN" },
  507.     { GPIO_TO_PIN(0, 3), GPIOF_IN,         "RTU_CHG_PG" },
  508.     { GPIO_TO_PIN(0, 5), GPIOF_IN,         "RTU_USB_OC_OUT" },
  509.     { GPIO_TO_PIN(0, 6), GPIOF_OUT_INIT_LOW,     "RTU_RUN_IND_LED" },
  510.     { GPIO_TO_PIN(1, 10), GPIOF_IN,         "RTU_TSC_BUSY"},
  511.     { GPIO_TO_PIN(1, 11), GPIOF_IN,        "RTU_PENIRQn" },
  512.     { GPIO_TO_PIN(1, 12), GPIOF_OUT_INIT_LOW, "RTU_uP_Q26x_RESET" },
  513.     { GPIO_TO_PIN(1, 13), GPIOF_OUT_INIT_HIGH, "RTU_uP_GPRS_PWR_EN" },
  514.     { GPIO_TO_PIN(1, 14), GPIOF_OUT_INIT_HIGH, "RTU_uP_Q26x_ON/OFF" },
  515.     { GPIO_TO_PIN(2, 1), GPIOF_OUT_INIT_LOW, "RTU_PLC_Reset" },
  516.     { GPIO_TO_PIN(2, 2), GPIOF_OUT_INIT_LOW, "RTU_PLC_T_Reg" },
  517.     { GPIO_TO_PIN(2, 4), GPIOF_OUT_INIT_LOW, "RTU_PLC_BAK_IO2" },
  518.     { GPIO_TO_PIN(2, 5), GPIOF_OUT_INIT_LOW, "RTU_RS485_RE" },
  519.     { GPIO_TO_PIN(2, 15), GPIOF_OUT_INIT_HIGH, "RTU_CHPWR_CS" },
  520.     { GPIO_TO_PIN(3, 9), GPIOF_OUT_INIT_HIGH, "RTU_RS485_DE" },
  521.     { GPIO_TO_PIN(6, 1), GPIOF_OUT_INIT_HIGH, "RTU_uP_VPIF_CLKO3" },
  522.     { GPIO_TO_PIN(6, 9), GPIOF_IN,         "RTU_KEY_IN2" },
  523.     { GPIO_TO_PIN(6, 11), GPIOF_IN,        "RTU_ALARM_IN5" },
  524.     { GPIO_TO_PIN(6, 15), GPIOF_OUT_INIT_HIGH,"RTU_uP_RESETOUTn" },
  525. };

  527. static int gpio_open(struct inode *inode,struct file *file)
  528. {
  529.     printk(KERN_WARNING"gpio open success!\n");
  530.     return 0;
  531. }

  533. static int gpio_release(struct inode *inode, struct file *filp)
  534. {
  535.   printk (KERN_ALERT "Device gpio released\n");
  536.   return 0;
  537. }

  539. static int gpio_read(struct file*f,char *dst,size_t size,loff_t*offset)
  540. {
  541.     unsigned char num;
  542.     __copy_to_user(&num,dst,1);
  543. #ifdef DEBUG
  544.      printk("__copy_to_user:%d\n",num);
  545. #endif

  547.     return 0;
  548. }

  550. static int gpio_write(struct file*f,const char *src,size_t size,loff_t *offset)
  551. {
  552.      unsigned char num;
  553.      __copy_from_user(&num,src,1);
  554. #ifdef DEBUG
  555.      printk("__copy_from_user:%d\n",num);
  556. #endif
  557.      return 0;

  559. }

  561. static long gpio_ioctl(struct file *file,unsigned int cmd,unsigned long gpio)
  562. {
  563.     int i;
  564.     unsigned long gpio_num = (gpio/100)*16+gpio%100;
  565.     for (i = 0; i < ARRAY_SIZE(gpio_array); i++) {
  566.         if(gpio_array[i].gpio == gpio_num)
  567.             goto valid_gpio;
  568.     }
  569.     return -1;
  570.         
  571. valid_gpio:
  572.     switch(cmd)//cmd表示应用程序传入的 GPIO 动作
  573.     {
  574.         case SET_OUTPUT_LOW://0
  575.         {
  576.             gpio_direction_output(gpio_num, 0);
  577.             break;
  578.         }
  579.         case SET_OUTPUT_HIGH://1
  580.         {
  581.             gpio_direction_output(gpio_num, 1);
  582.             break;
  583.         }
  584.         case GET_VALUE://2
  585.         {
  586.             return gpio_get_value(gpio_num);    
  587.         }
  588.         case SET_INPUT://3
  589.         {
  590.             gpio_direction_input(gpio_num);
  591.             break;
  592.         }
  593.         default:
  594.         {
  595.             printk(KERN_EMERG "GPIO command mistake!!!\n");
  596.             break;
  597.         }
  598.     }
  599.     return 0;
  600. }
  601.         
  602. static const struct file_operations gpio_fops =
  603. {
  604.   .owner = THIS_MODULE,
  605.   .open = gpio_open,
  606.   .release = gpio_release,
  607.   .read = gpio_read,
  608.   .write = gpio_write,
  609.   .unlocked_ioctl = gpio_ioctl,
  610. };

  612. static int __init gpio_init(void) /*内核初始化会调用该函数*/
  613. {
  614.     int ret;
  615.     
  616.     ret = gpio_request_array(gpio_array, ARRAY_SIZE(gpio_array));
  617.     if (ret < 0)
  618.     {
  619.         printk(KERN_EMERG "GPIO request failed\n");
  620.         goto request_failed;
  621.     }
  622.     
  623.     dev_t my_dev_no;
  624.     struct cdev *gpio_cdev;
  625.     gpio_cdev = cdev_alloc();
  626.     if(gpio_cdev == NULL)
  627.     {
  628.         printk(KERN_EMERG "Cannot alloc cdev\n");
  629.         goto request_failed;
  630.     }
  631.     cdev_init(gpio_cdev,&gpio_fops);
  632.     gpio_cdev->owner=THIS_MODULE;
  633.     int result=alloc_chrdev_region(&my_dev_no,0,1,DEVICE_NAME);
  634.     if(result < 0)
  635.     {
  636.         printk(KERN_EMERG "alloc_chrdev_region failed\n");
  637.         goto request_failed;
  638.     }
  639.     ret=cdev_add(gpio_cdev,my_dev_no,1);
  640.     
  641.     
  642.   ret = register_chrdev(GPIO_MAJOR, DEVICE_NAME, &gpio_fops);//驱动字符设备
  643.      if(ret < 0)
  644.      {
  645.     printk(KERN_EMERG "GPIO register failed\n");
  646.     goto request_failed;
  647.      }
  648.     
  649.     //在sysfs文件系统下创建一个类
  650.   gpio_class = class_create(THIS_MODULE, DEVICE_NAME);
  651.   //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
  652.     device_create(gpio_class, NULL, MKDEV(GPIO_MAJOR, GPIO_MINOR), NULL, DEVICE_NAME);
  653.     return ret;
  654.     
  655. request_failed:
  656.     gpio_free_array(gpio_array, ARRAY_SIZE(gpio_array));
  657.     return ret;
  658. }

  660. static void __exit gpio_exit(void)
  661. {
  662.     device_destroy(gpio_class, MKDEV(GPIO_MAJOR, GPIO_MINOR));
  663.   class_unregister(gpio_class);
  664.   class_destroy(gpio_class);
  665.   unregister_chrdev(GPIO_MAJOR, DEVICE_NAME);
  666. }

  668. module_init(gpio_init);
  669. module_exit(gpio_exit);
  670. MODULE_LICENSE("GPL");
  671. MODULE_VERSION ("v2.0");
  672. MODULE_AUTHOR("wbl <>");
  673. MODULE_DESCRIPTION("OMAPL138 GPIO driver");


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