關於關於驅動設備模型相關概念請參考《Linux Device Drivers》等相關書籍,和內核源碼目錄...\Documentation\driver-model
簡單來說總線(bus),驅動(driver),設備(device)這三者之間的關系就是:驅動開發者可以通過總線(bus)來將驅動(driver)和設備(device)進行隔離,這樣的好處就是開發者可以將相對穩定不變的驅動(driver)獨立起來,可以通過總線(bus)來橋接與之匹配的設備(device)。設備(device)只需要提供與硬件相關的底層硬件的配置,如io,中斷等。
platform.c 提供了一個平台總線(platform_bus),和注冊平台設備(platform_device)和平台驅動(platform_driver)的相關接口,其中平台總線(platform_bus)已經編進內核,開發者只需要提供平台設備(platform_device)和平台驅動(platform_driver)的相關代碼就行了。
在linux源碼目錄\drivers\input\keyboard下,提供了一個gpio_keys.c的平台驅動(platform_driver),這個就是一個簡單地按鍵驅動,檢測到按鍵狀態,上報給輸入子系統。
因此,開發者需要做的就是提供一個平台設備(platform_device),以向平台驅動(platform_driver)提供相關的硬件配置,如按鍵IO,中斷號,按鍵碼等等。
gpio_keys.c (不用任何改動)
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()中調用了request_irq(..., pdev), 34 * 因此dev_id指向了platform_device *pdev,通過dev_id間接傳遞 35 * platform_device *指針 36 */ 37 struct platform_device *pdev = dev_id; 38 /* [cgw]: 當platform_device 和 platform_driver匹配時,會通過 39 * probe()傳遞platform_device進來。在注冊platform_device時, 40 * platform_device.dev.platform_data必須指向gpio_keys_platform_data * 41 */ 42 struct gpio_keys_platform_data *pdata = pdev->dev.platform_data; 43 /* [cgw]: probe()中已分配了一個struct input_dev,並通過platform_set_drvdata() 44 * 設置platform_device->dev->driver_data = input; 45 */ 46 struct input_dev *input = platform_get_drvdata(pdev); 47 48 /* [cgw]: 輪詢pdata->nbuttons個按鍵 */ 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]: 某個gpio發生了中斷 */ 54 if (irq == gpio_to_irq(gpio)) { 55 /* [cgw]: 獲得按鍵類型 */ 56 unsigned int type = button->type ?: EV_KEY; 57 /* [cgw]: 獲取按鍵狀態 */ 58 int state = (gpio_get_value(gpio) ? 1 : 0) ^ button->active_low; 59 /* [cgw]: 發送按鍵事件 */ 60 input_event(input, type, button->code, !!state); 61 /* [cgw]: 發送同步事件 */ 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()中調用了request_irq(..., pdev), 72 * 因此dev_id指向了platform_device *pdev,通過dev_id間接傳遞 73 * platform_device *指針 74 */ 75 struct gpio_keys_platform_data *pdata = pdev->dev.platform_data; 76 struct input_dev *input; 77 int i, error; 78 79 /* [cgw]: 分配一個輸入設備 */ 80 input = input_allocate_device(); 81 /* [cgw]: 分配失敗 */ 82 if (!input) 83 return -ENOMEM; 84 85 /* [cgw]: 設置platform_device->dev->driver_data = input */ 86 platform_set_drvdata(pdev, input); 87 88 /* [cgw]: 設置evdev.c支持的事件類型 */ 89 input->evbit[0] = BIT(EV_KEY); 90 /* [cgw]: 設置輸入設備名,同platform_device的名字 */ 91 input->name = pdev->name; 92 /* [cgw]: */ 93 input->phys = "gpio-keys/input0"; 94 /* [cgw]: 設置輸入設備dev的父節點為platform_device->dev */ 95 input->dev.parent = &pdev->dev; 96 97 /* [cgw]: 設置輸入設備總線類型,供應商,產品,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]: 為pdata->nbuttons個按鍵申請中斷 */ 104 for (i = 0; i < pdata->nbuttons; i++) { 105 struct gpio_keys_button *button = &pdata->buttons[i]; 106 /* [cgw]: 獲得gpio對應的中斷號 */ 107 int irq = gpio_to_irq(button->gpio); 108 /* [cgw]: 獲得按鍵類型 */ 109 unsigned int type = button->type ?: EV_KEY; 110 111 /* [cgw]: 設置中斷類型為邊沿中斷 */ 112 set_irq_type(irq, IRQ_TYPE_EDGE_BOTH); 113 /* [cgw]: 申請中斷,設置中斷服務程序 */ 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]: 設置evdev.c支持的按鍵碼 */ 124 input_set_capability(input, type, button->code); 125 } 126 127 /* [cgw]: 注冊一個輸入設備 */ 128 error = input_register_device(input); 129 /* [cgw]: 注冊失敗 */ 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]: 釋放中斷 */ 139 for (i = i - 1; i >= 0; i--) 140 free_irq(gpio_to_irq(pdata->buttons[i].gpio), pdev); 141 /* [cgw]: 釋放輸入設備占用的內存 */ 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()中調用了request_irq(..., pdev), 150 * 因此dev_id指向了platform_device *pdev,通過dev_id間接傳遞 151 * platform_device *指針 152 */ 153 struct gpio_keys_platform_data *pdata = pdev->dev.platform_data; 154 /* [cgw]: probe()中已分配了一個struct input_dev,並通過platform_set_drvdata() 155 * 設置platform_device->dev->driver_data = input; 156 */ 157 struct input_dev *input = platform_get_drvdata(pdev); 158 int i; 159 160 /* [cgw]: 釋放中斷 */ 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]: 注銷輸入設備 */ 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]: 注冊gpio_keys_device_driver平台驅動 */ 183 return platform_driver_register(&gpio_keys_device_driver); 184 } 185 186 static void __exit gpio_keys_exit(void) 187 { 188 /* [cgw]: 注銷gpio_keys_device_driver平台驅動 */ 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");
平台設備(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]: 設置四個按鍵的鍵碼,按鍵io,激活狀態,按鍵名,按鍵類型 */ 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]: 分配一個平台設備 */ 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]: 注冊keys_platform_dev平台設備 */ 82 platform_device_register(&keys_platform_dev); 83 return 0; 84 } 85 86 static void keys_dev_exit(void) 87 { 88 /* [cgw]: 注銷keys_platform_dev平台設備 */ 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");
應用測試程序:
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]: 異步通知產生時返回的數據 */ 22 read(fd, &buttons_event, sizeof(struct input_event)); 23 24 /* [cgw]: 打印事件類型,事件碼,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]: 設置文件標識符 */ 48 fds[0].fd = fd; 49 /* [cgw]: 設置應用程序要響應的事件 */ 50 fds[0].events = POLLIN; 51 52 while (1) 53 { 54 /* [cgw]: 休眠5S */ 55 ret = poll(fds, 1, 5000); 56 57 /* [cgw]: 喚醒或超時 */ 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 }
平台設備(platform_device) keys_platform_dev 是怎樣找到與之匹配的平台驅動(platform_driver) gpio_keys_device_driver的呢?
因為他們都注冊到了平台總線(platform_bus)上。平台驅動(platform_driver)和平台設備(platform_device)會相互查找彼此是否匹配,匹配的條件就是,
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 即他們的名字就是:“gpio-keys”
一旦匹配,就會調用
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()
這樣平台驅動(platform_driver)就可以獲得平台設備(platform_device)的 struct platform_device結構的數據了,即keys_platform_dev,從這個結構就可以獲得相關配置,以使能平台驅動(platform_driver) gpio_keys.c中相應的IO和中斷。
實驗現象:
# insmod gpio_keys.ko //安裝平台驅動(platform_driver) # insmod keys_dev.ko //安裝平台設備(platform_device) input: gpio-keys as /class/input/input1 # ./platform_test //運行應用測試程序 Ver:0x10000 //用ioctl獲取輸入子系統的版本號 type: 0x1 code: 0x2e value: 0x1 //按下"C"鍵 type: 0x0 code: 0x0 value: 0x0 //因為調用了input_sync() type: 0x1 code: 0x2e value: 0x0 //松開(彈起)"C"鍵 type: 0x0 code: 0x0 value: 0x0 //因為調用了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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