设备模型(device-model)之平台总线(bus),驱动(driver),设备(device)
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关于关于驱动设备模型相关概念请参考《Linux Device Drivers》等相关书籍,和内核源码目录...\Documentation\driver-model
简单来说总线(bus),驱动(driver),设备(device)这三者之间的关系就是:驱动开发者可以通过总线(bus)来将驱动(driver)和设备(device)进行隔离,这样的好处就是开发者可以将相对稳定不变的驱动(driver)独立起来,可以通过总线(bus)来桥接与之匹配的设备(device)。设备(device)只需要提供与硬件相关的底层硬件的配置,如io,中断等。
platform.c 提供了一个平台总线(platform_bus),和注册平台设备(platform_device)和平台驱动(platform_driver)的相关接口,其中平台总线(platform_bus)已经编进内核,开发者只需要提供平台设备(platform_device)和平台驱动(platform_driver)的相关代码就行了。
在linux源码目录\drivers\input\keyboard下,提供了一个gpio_keys.c的平台驱动(platform_driver),这个就是一个简单地按键驱动,检测到按键状态,上报给输入子系统。
因此,开发者需要做的就是提供一个平台设备(platform_device),以向平台驱动(platform_driver)提供相关的硬件配置,如按键IO,中断号,按键码等等。
gpio_keys.c (不用任何改动)
1 /* 2 * Driver for keys on GPIO lines capable of generating interrupts. 3 * 4 * Copyright 2005 Phil Blundell 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 */ 10 11 #include <linux/module.h> 12 #include <linux/version.h> 13 14 #include <linux/init.h> 15 #include <linux/fs.h> 16 #include <linux/interrupt.h> 17 #include <linux/irq.h> 18 #include <linux/sched.h> 19 #include <linux/pm.h> 20 #include <linux/sysctl.h> 21 #include <linux/proc_fs.h> 22 #include <linux/delay.h> 23 #include <linux/platform_device.h> 24 #include <linux/input.h> 25 #include <linux/irq.h> 26 #include <linux/gpio_keys.h> 27 28 #include <asm/gpio.h> 29 30 static irqreturn_t gpio_keys_isr(int irq, void *dev_id) 31 { 32 int i; 33 /* [cgw]: 在gpio_keys_probe()中调用了request_irq(..., pdev), 34 * 因此dev_id指向了platform_device *pdev,通过dev_id间接传递 35 * platform_device *指针 36 */ 37 struct platform_device *pdev = dev_id; 38 /* [cgw]: 当platform_device 和 platform_driver匹配时,会通过 39 * probe()传递platform_device进来。在注册platform_device时, 40 * platform_device.dev.platform_data必须指向gpio_keys_platform_data * 41 */ 42 struct gpio_keys_platform_data *pdata = pdev->dev.platform_data; 43 /* [cgw]: probe()中已分配了一个struct input_dev,并通过platform_set_drvdata() 44 * 设置platform_device->dev->driver_data = input; 45 */ 46 struct input_dev *input = platform_get_drvdata(pdev); 47 48 /* [cgw]: 轮询pdata->nbuttons个按键 */ 49 for (i = 0; i < pdata->nbuttons; i++) { 50 struct gpio_keys_button *button = &pdata->buttons[i]; 51 int gpio = button->gpio; 52 53 /* [cgw]: 某个gpio发生了中断 */ 54 if (irq == gpio_to_irq(gpio)) { 55 /* [cgw]: 获得按键类型 */ 56 unsigned int type = button->type ?: EV_KEY; 57 /* [cgw]: 获取按键状态 */ 58 int state = (gpio_get_value(gpio) ? 1 : 0) ^ button->active_low; 59 /* [cgw]: 发送按键事件 */ 60 input_event(input, type, button->code, !!state); 61 /* [cgw]: 发送同步事件 */ 62 input_sync(input); 63 } 64 } 65 66 return IRQ_HANDLED; 67 } 68 69 static int __devinit gpio_keys_probe(struct platform_device *pdev) 70 { 71 /* [cgw]: 在gpio_keys_probe()中调用了request_irq(..., pdev), 72 * 因此dev_id指向了platform_device *pdev,通过dev_id间接传递 73 * platform_device *指针 74 */ 75 struct gpio_keys_platform_data *pdata = pdev->dev.platform_data; 76 struct input_dev *input; 77 int i, error; 78 79 /* [cgw]: 分配一个输入设备 */ 80 input = input_allocate_device(); 81 /* [cgw]: 分配失败 */ 82 if (!input) 83 return -ENOMEM; 84 85 /* [cgw]: 设置platform_device->dev->driver_data = input */ 86 platform_set_drvdata(pdev, input); 87 88 /* [cgw]: 设置evdev.c支持的事件类型 */ 89 input->evbit[0] = BIT(EV_KEY); 90 /* [cgw]: 设置输入设备名,同platform_device的名字 */ 91 input->name = pdev->name; 92 /* [cgw]: */ 93 input->phys = "gpio-keys/input0"; 94 /* [cgw]: 设置输入设备dev的父节点为platform_device->dev */ 95 input->dev.parent = &pdev->dev; 96 97 /* [cgw]: 设置输入设备总线类型,供应商,产品,版本 */ 98 input->id.bustype = BUS_HOST; 99 input->id.vendor = 0x0001; 100 input->id.product = 0x0001; 101 input->id.version = 0x0100; 102 103 /* [cgw]: 为pdata->nbuttons个按键申请中断 */ 104 for (i = 0; i < pdata->nbuttons; i++) { 105 struct gpio_keys_button *button = &pdata->buttons[i]; 106 /* [cgw]: 获得gpio对应的中断号 */ 107 int irq = gpio_to_irq(button->gpio); 108 /* [cgw]: 获得按键类型 */ 109 unsigned int type = button->type ?: EV_KEY; 110 111 /* [cgw]: 设置中断类型为边沿中断 */ 112 set_irq_type(irq, IRQ_TYPE_EDGE_BOTH); 113 /* [cgw]: 申请中断,设置中断服务程序 */ 114 error = request_irq(irq, gpio_keys_isr, IRQF_SAMPLE_RANDOM, 115 button->desc ? button->desc : "gpio_keys", 116 pdev); 117 if (error) { 118 printk(KERN_ERR "gpio-keys: unable to claim irq %d; error %d\n", 119 irq, error); 120 goto fail; 121 } 122 123 /* [cgw]: 设置evdev.c支持的按键码 */ 124 input_set_capability(input, type, button->code); 125 } 126 127 /* [cgw]: 注册一个输入设备 */ 128 error = input_register_device(input); 129 /* [cgw]: 注册失败 */ 130 if (error) { 131 printk(KERN_ERR "Unable to register gpio-keys input device\n"); 132 goto fail; 133 } 134 135 return 0; 136 137 fail: 138 /* [cgw]: 释放中断 */ 139 for (i = i - 1; i >= 0; i--) 140 free_irq(gpio_to_irq(pdata->buttons[i].gpio), pdev); 141 /* [cgw]: 释放输入设备占用的内存 */ 142 input_free_device(input); 143 144 return error; 145 } 146 147 static int __devexit gpio_keys_remove(struct platform_device *pdev) 148 { 149 /* [cgw]: 在gpio_keys_probe()中调用了request_irq(..., pdev), 150 * 因此dev_id指向了platform_device *pdev,通过dev_id间接传递 151 * platform_device *指针 152 */ 153 struct gpio_keys_platform_data *pdata = pdev->dev.platform_data; 154 /* [cgw]: probe()中已分配了一个struct input_dev,并通过platform_set_drvdata() 155 * 设置platform_device->dev->driver_data = input; 156 */ 157 struct input_dev *input = platform_get_drvdata(pdev); 158 int i; 159 160 /* [cgw]: 释放中断 */ 161 for (i = 0; i < pdata->nbuttons; i++) { 162 int irq = gpio_to_irq(pdata->buttons[i].gpio); 163 free_irq(irq, pdev); 164 } 165 166 /* [cgw]: 注销输入设备 */ 167 input_unregister_device(input); 168 169 return 0; 170 } 171 172 struct platform_driver gpio_keys_device_driver = { 173 .probe = gpio_keys_probe, 174 .remove = __devexit_p(gpio_keys_remove), 175 .driver = { 176 .name = "gpio-keys", 177 } 178 }; 179 180 static int __init gpio_keys_init(void) 181 { 182 /* [cgw]: 注册gpio_keys_device_driver平台驱动 */ 183 return platform_driver_register(&gpio_keys_device_driver); 184 } 185 186 static void __exit gpio_keys_exit(void) 187 { 188 /* [cgw]: 注销gpio_keys_device_driver平台驱动 */ 189 platform_driver_unregister(&gpio_keys_device_driver); 190 } 191 192 module_init(gpio_keys_init); 193 module_exit(gpio_keys_exit); 194 195 MODULE_LICENSE("GPL"); 196 MODULE_AUTHOR("Phil Blundell <[email protected]>"); 197 MODULE_DESCRIPTION("Keyboard driver for CPU GPios");
平台设备(platform_device):
keys_dev.c
1 #include <linux/module.h> 2 #include <linux/version.h> 3 4 #include <linux/init.h> 5 6 #include <linux/kernel.h> 7 #include <linux/types.h> 8 #include <linux/interrupt.h> 9 #include <linux/list.h> 10 #include <linux/timer.h> 11 #include <linux/init.h> 12 #include <linux/serial_core.h> 13 #include <linux/platform_device.h> 14 #include <linux/gpio_keys.h> 15 #include <linux/input.h> 16 #include <linux/irq.h> 17 18 #include <asm/gpio.h> 19 #include <asm/io.h> 20 #include <asm/arch/regs-gpio.h> 21 22 /* [cgw]: 设置四个按键的键码,按键io,激活状态,按键名,按键类型 */ 23 static struct gpio_keys_button keys_buff[4] = { 24 { 25 KEY_A, 26 S3C2410_GPF0, 27 1, 28 "A", 29 EV_KEY 30 }, 31 32 { 33 KEY_B, 34 S3C2410_GPF2, 35 1, 36 "B", 37 EV_KEY 38 }, 39 40 { 41 KEY_C, 42 S3C2410_GPG3, 43 1, 44 "C", 45 EV_KEY 46 }, 47 48 { 49 KEY_D, 50 S3C2410_GPG11, 51 1, 52 "D", 53 EV_KEY 54 }, 55 }; 56 57 58 static struct gpio_keys_platform_data keys_dev = { 59 .buttons = &keys_buff[0], 60 .nbuttons = ARRAY_SIZE(keys_buff) 61 }; 62 63 static void keys_dev_release(struct device * dev) 64 { 65 printk("keys_dev_release! \n"); 66 } 67 68 /* [cgw]: 分配一个平台设备 */ 69 static struct platform_device keys_platform_dev = { 70 .name = "gpio-keys", 71 .id = -1, 72 .dev = { 73 .release = keys_dev_release, 74 .platform_data = (void *)&keys_dev, 75 }, 76 }; 77 78 79 static int keys_dev_init(void) 80 { 81 /* [cgw]: 注册keys_platform_dev平台设备 */ 82 platform_device_register(&keys_platform_dev); 83 return 0; 84 } 85 86 static void keys_dev_exit(void) 87 { 88 /* [cgw]: 注销keys_platform_dev平台设备 */ 89 platform_device_unregister(&keys_platform_dev); 90 } 91 92 module_init(keys_dev_init); 93 module_exit(keys_dev_exit); 94 95 MODULE_LICENSE("GPL");
应用测试程序:
platform_test.c
1 #include <sys/types.h> 2 #include <sys/stat.h> 3 #include <fcntl.h> 4 #include <stdio.h> 5 #include <poll.h> 6 #include <signal.h> 7 #include <sys/types.h> 8 #include <unistd.h> 9 #include <fcntl.h> 10 11 #include <linux/input.h> 12 13 14 15 int fd; 16 17 void my_signal_fun(int signum) 18 { 19 struct input_event buttons_event; 20 21 /* [cgw]: 异步通知产生时返回的数据 */ 22 read(fd, &buttons_event, sizeof(struct input_event)); 23 24 /* [cgw]: 打印事件类型,事件码,事件值 */ 25 printf("type: 0x%x code: 0x%x value: 0x%x\n", 26 buttons_event.type, 27 buttons_event.code, 28 buttons_event.value); 29 } 30 31 int main(int argc, char **argv) 32 { 33 int ret, arg; 34 struct pollfd fds[1]; 35 unsigned long ver = 0; 36 37 fd = open("/dev/event1", O_RDWR | O_NONBLOCK); 38 39 if (fd < 0) 40 { 41 printf("can‘t open!\n"); 42 } 43 44 ioctl(fd, EVIOCGVERSION, &ver); 45 printf("Ver:0x%x \n", ver); 46 47 /* [cgw]: 设置文件标识符 */ 48 fds[0].fd = fd; 49 /* [cgw]: 设置应用程序要响应的事件 */ 50 fds[0].events = POLLIN; 51 52 while (1) 53 { 54 /* [cgw]: 休眠5S */ 55 ret = poll(fds, 1, 5000); 56 57 /* [cgw]: 唤醒或超时 */ 58 //printf("wake up!\n"); 59 if (ret == 0) 60 { 61 printf("time out\n"); 62 } 63 else 64 { 65 my_signal_fun(arg); 66 } 67 } 68 69 close(fd); 70 71 return 0; 72 }
平台设备(platform_device) keys_platform_dev 是怎样找到与之匹配的平台驱动(platform_driver) gpio_keys_device_driver的呢?
因为他们都注册到了平台总线(platform_bus)上。平台驱动(platform_driver)和平台设备(platform_device)会相互查找彼此是否匹配,匹配的条件就是,
1 static int platform_match(struct device * dev, struct device_driver * drv) 2 { 3 struct platform_device *pdev = container_of(dev, struct platform_device, dev); 4 5 return (strncmp(pdev->name, drv->name, BUS_ID_SIZE) == 0); 6 }
platform_device->name == platform_driver->driver->name 即他们的名字就是:“gpio-keys”
一旦匹配,就会调用
1 static int platform_drv_probe(struct device *_dev) 2 { 3 struct platform_driver *drv = to_platform_driver(_dev->driver); 4 struct platform_device *dev = to_platform_device(_dev); 5 6 return drv->probe(dev); 7 }
drv->probe() = platform_driver->probe() = gpio_keys_probe()
这样平台驱动(platform_driver)就可以获得平台设备(platform_device)的 struct platform_device结构的数据了,即keys_platform_dev,从这个结构就可以获得相关配置,以使能平台驱动(platform_driver) gpio_keys.c中相应的IO和中断。
实验现象:
# insmod gpio_keys.ko //安装平台驱动(platform_driver) # insmod keys_dev.ko //安装平台设备(platform_device) input: gpio-keys as /class/input/input1 # ./platform_test //运行应用测试程序 Ver:0x10000 //用ioctl获取输入子系统的版本号 type: 0x1 code: 0x2e value: 0x1 //按下"C"键 type: 0x0 code: 0x0 value: 0x0 //因为调用了input_sync() type: 0x1 code: 0x2e value: 0x0 //松开(弹起)"C"键 type: 0x0 code: 0x0 value: 0x0 //因为调用了input_sync() type: 0x1 code: 0x30 value: 0x1 //... ... type: 0x0 code: 0x0 value: 0x0 type: 0x1 code: 0x30 value: 0x0 type: 0x0 code: 0x0 value: 0x0 type: 0x1 code: 0x1e value: 0x1 type: 0x0 code: 0x0 value: 0x0 type: 0x1 code: 0x1e value: 0x0 type: 0x0 code: 0x0 value: 0x0 type: 0x1 code: 0x20 value: 0x1 type: 0x0 code: 0x0 value: 0x0 type: 0x1 code: 0x20 value: 0x0 type: 0x0 code: 0x0 value: 0x0 time out time out time out
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