基於RK3188平臺LED驅動程式的移植的移植。如有不正確之處，歡迎大家指點。
本文的LED驅動程式不是通過開啟裝置節點來訪問和控制LED的，是通過sys檔案系統來控制LED。
板子上有四盞燈以及對應的GPIO的引腳如下：
基於sys檔案系統的LED驅動核心已經提供了，我們需要做的事情沒有那麼多。核心通過的LED驅動程式走的是平臺匯流排的方式，板級檔案Board-rk3188-u4301.c (kernel\arch\arm\mach-rk3188) 裡新增LED的GPIO的資訊。
1 static struct gpio_led rk29_leds[] = { 2 { 3 .name = "power", //在/sys/class/leds/ 目錄下顯示的檔名 4 .gpio = RK30_PIN0_PB4, //LED的GPIO口的引腳 5 .default_state = LEDS_GPIO_DEFSTATE_OFF, //設定預設的狀態 6 }, 7 { 8 .name = "paper", 9 .gpio = RK30_PIN0_PB5, 10 .default_state = LEDS_GPIO_DEFSTATE_OFF, 11 }, 12 { 13 .name = "connect", 14 .gpio = RK30_PIN0_PB6, 15 .default_state = LEDS_GPIO_DEFSTATE_OFF, 16 }, 17 { 18 .name = "status", 19 .gpio = RK30_PIN0_PB7, 20 .default_state = LEDS_GPIO_DEFSTATE_OFF, 21 }, 22 }; 23 24 static struct gpio_led_platform_data rk29_leds_pdata = { 25 .leds = rk29_leds, 26 .num_leds = ARRAY_SIZE(rk29_leds), 27 }; 28 29 static struct platform_device rk29_device_gpio_leds = { 30 .name = "leds-gpio", //裝置的名稱，驅動就是根據這個檔案匹配的啊。 31 .id = -1, 32 .dev = { 33 .platform_data = &rk29_leds_pdata, 34 }, 35 };
我們在看看驅動檔案Leds-gpio.c (\\192.168.1.144\zsf\rk3188_5.1\android\kernel\drivers\leds)
1 /* 2 * LEDs driver for GPIOs 3 * 4 * Copyright (C) 2007 8D Technologies inc. 5 * Raphael Assenat <raph@8d.com> 6 * Copyright (C) 2008 Freescale Semiconductor, Inc. 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 * 12 */ 13 #include <linux/kernel.h> 14 #include <linux/init.h> 15 #include <linux/platform_device.h> 16 #include <linux/leds.h> 17 #include <linux/of_platform.h> 18 #include <linux/of_gpio.h> 19 #include <linux/slab.h> 20 #include <linux/workqueue.h> 21 22 #include <asm/gpio.h> 23 24 struct gpio_led_data { 25 struct led_classdev cdev; 26 unsigned gpio; 27 struct work_struct work; 28 u8 new_level; 29 u8 can_sleep; 30 u8 active_low; 31 u8 blinking; 32 int (*platform_gpio_blink_set)(unsigned gpio, int state, 33 unsigned long *delay_on, unsigned long *delay_off); 34 }; 35 36 static void gpio_led_work(struct work_struct *work) 37 { 38 struct gpio_led_data *led_dat = 39 container_of(work, struct gpio_led_data, work); 40 41 if (led_dat->blinking) { 42 led_dat->platform_gpio_blink_set(led_dat->gpio, 43 led_dat->new_level, 44 NULL, NULL); 45 led_dat->blinking = 0; 46 } else 47 gpio_set_value_cansleep(led_dat->gpio, led_dat->new_level); 48 } 49 50 static void gpio_led_set(struct led_classdev *led_cdev, 51 enum led_brightness value) 52 { 53 struct gpio_led_data *led_dat = 54 container_of(led_cdev, struct gpio_led_data, cdev); 55 int level; 56 57 if (value == LED_OFF) 58 level = 0; 59 else 60 level = 1; 61 62 if (led_dat->active_low) 63 level = !level; 64 65 /* Setting GPIOs with I2C/etc requires a task context, and we don't 66 * seem to have a reliable way to know if we're already in one; so 67 * let's just assume the worst. 68 */ 69 if (led_dat->can_sleep) { 70 led_dat->new_level = level; 71 schedule_work(&led_dat->work); 72 } else { 73 if (led_dat->blinking) { 74 led_dat->platform_gpio_blink_set(led_dat->gpio, level, 75 NULL, NULL); 76 led_dat->blinking = 0; 77 } else 78 gpio_set_value(led_dat->gpio, level); 79 } 80 } 81 82 static int gpio_blink_set(struct led_classdev *led_cdev, 83 unsigned long *delay_on, unsigned long *delay_off) 84 { 85 struct gpio_led_data *led_dat = 86 container_of(led_cdev, struct gpio_led_data, cdev); 87 88 led_dat->blinking = 1; 89 return led_dat->platform_gpio_blink_set(led_dat->gpio, GPIO_LED_BLINK, 90 delay_on, delay_off); 91 } 92 93 static int __devinit create_gpio_led(const struct gpio_led *template, 94 struct gpio_led_data *led_dat, struct device *parent, 95 int (*blink_set)(unsigned, int, unsigned long *, unsigned long *)) 96 { 97 int ret, state; 98 99 led_dat->gpio = -1; 100 101 /* skip leds that aren't available */ 102 if (!gpio_is_valid(template->gpio)) { 103 printk(KERN_INFO "Skipping unavailable LED gpio %d (%s)\n", 104 template->gpio, template->name); 105 return 0; 106 } 107 108 ret = gpio_request(template->gpio, template->name); 109 if (ret < 0) 110 return ret; 111 112 led_dat->cdev.name = template->name; 113 led_dat->cdev.default_trigger = template->default_trigger; 114 led_dat->gpio = template->gpio; 115 led_dat->can_sleep = gpio_cansleep(template->gpio); 116 led_dat->active_low = template->active_low; 117 led_dat->blinking = 0; 118 if (blink_set) { 119 led_dat->platform_gpio_blink_set = blink_set; 120 led_dat->cdev.blink_set = gpio_blink_set; 121 } 122 led_dat->cdev.brightness_set = gpio_led_set; 123 if (template->default_state == LEDS_GPIO_DEFSTATE_KEEP) 124 state = !!gpio_get_value(led_dat->gpio) ^ led_dat->active_low; 125 else 126 state = (template->default_state == LEDS_GPIO_DEFSTATE_ON); 127 led_dat->cdev.brightness = state ? LED_FULL : LED_OFF; 128 if (!template->retain_state_suspended) 129 led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME; 130 131 ret = gpio_direction_output(led_dat->gpio, led_dat->active_low ^ state); 132 if (ret < 0) 133 goto err; 134 135 INIT_WORK(&led_dat->work, gpio_led_work); 136 137 ret = led_classdev_register(parent, &led_dat->cdev); 138 if (ret < 0) 139 goto err; 140 141 return 0; 142 err: 143 gpio_free(led_dat->gpio); 144 return ret; 145 } 146 147 static void delete_gpio_led(struct gpio_led_data *led) 148 { 149 if (!gpio_is_valid(led->gpio)) 150 return; 151 led_classdev_unregister(&led->cdev); 152 cancel_work_sync(&led->work); 153 gpio_free(led->gpio); 154 } 155 156 struct gpio_leds_priv { 157 int num_leds; 158 struct gpio_led_data leds[]; 159 }; 160 161 static inline int sizeof_gpio_leds_priv(int num_leds) 162 { 163 return sizeof(struct gpio_leds_priv) + 164 (sizeof(struct gpio_led_data) * num_leds); 165 } 166 167 /* Code to create from OpenFirmware platform devices */ 168 #ifdef CONFIG_LEDS_GPIO_OF 169 static struct gpio_leds_priv * __devinit gpio_leds_create_of(struct platform_device *pdev) 170 { 171 struct device_node *np = pdev->dev.of_node, *child; 172 struct gpio_leds_priv *priv; 173 int count = 0, ret; 174 175 /* count LEDs in this device, so we know how much to allocate */ 176 for_each_child_of_node(np, child) 177 count++; 178 if (!count) 179 return NULL; 180 181 priv = kzalloc(sizeof_gpio_leds_priv(count), GFP_KERNEL); 182 if (!priv) 183 return NULL; 184 185 for_each_child_of_node(np, child) { 186 struct gpio_led led = {}; 187 enum of_gpio_flags flags; 188 const char *state; 189 190 led.gpio = of_get_gpio_flags(child, 0, &flags); 191 led.active_low = flags & OF_GPIO_ACTIVE_LOW; 192 led.name = of_get_property(child, "label", NULL) ? : child->name; 193 led.default_trigger = 194 of_get_property(child, "linux,default-trigger", NULL); 195 state = of_get_property(child, "default-state", NULL); 196 if (state) { 197 if (!strcmp(state, "keep")) 198 led.default_state = LEDS_GPIO_DEFSTATE_KEEP; 199 else if (!strcmp(state, "on")) 200 led.default_state = LEDS_GPIO_DEFSTATE_ON; 201 else 202 led.default_state = LEDS_GPIO_DEFSTATE_OFF; 203 } 204 205 ret = create_gpio_led(&led, &priv->leds[priv->num_leds++], 206 &pdev->dev, NULL); 207 if (ret < 0) { 208 of_node_put(child); 209 goto err; 210 } 211 } 212 213 return priv; 214 215 err: 216 for (count = priv->num_leds - 2; count >= 0; count--) 217 delete_gpio_led(&priv->leds[count]); 218 kfree(priv); 219 return NULL; 220 } 221 222 static const struct of_device_id of_gpio_leds_match[] = { 223 { .compatible = "gpio-leds", }, 224 {}, 225 }; 226 #else 227 static struct gpio_leds_priv * __devinit gpio_leds_create_of(struct platform_device *pdev) 228 { 229 return NULL; 230 } 231 #define of_gpio_leds_match NULL 232 #endif 233 234 235 static int __devinit gpio_led_probe(struct platform_device *pdev) 236 { 237 struct gpio_led_platform_data *pdata = pdev->dev.platform_data; 238 struct gpio_leds_priv *priv; 239 int i, ret = 0; 240 241 if (pdata && pdata->num_leds) { 242 priv = kzalloc(sizeof_gpio_leds_priv(pdata->num_leds), 243 GFP_KERNEL); 244 if (!priv) 245 return -ENOMEM; 246 247 priv->num_leds = pdata->num_leds; 248 for (i = 0; i < priv->num_leds; i++) { 249 ret = create_gpio_led(&pdata->leds[i], 250 &priv->leds[i], 251 &pdev->dev, pdata->gpio_blink_set); 252 if (ret < 0) { 253 /* On failure: unwind the led creations */ 254 for (i = i - 1; i >= 0; i--) 255 delete_gpio_led(&priv->leds[i]); 256 kfree(priv); 257 return ret; 258 } 259 } 260 } else { 261 priv = gpio_leds_create_of(pdev); 262 if (!priv) 263 return -ENODEV; 264 } 265 266 platform_set_drvdata(pdev, priv); 267 268 return 0; 269 } 270 271 static int __devexit gpio_led_remove(struct platform_device *pdev) 272 { 273 struct gpio_leds_priv *priv = dev_get_drvdata(&pdev->dev); 274 int i; 275 276 for (i = 0; i < priv->num_leds; i++) 277 delete_gpio_led(&priv->leds[i]); 278 279 dev_set_drvdata(&pdev->dev, NULL); 280 kfree(priv); 281 282 return 0; 283 } 284 285 static struct platform_driver gpio_led_driver = { 286 .probe = gpio_led_probe, 287 .remove = __devexit_p(gpio_led_remove), 288 .driver = { 289 .name = "leds-gpio", 290 .owner = THIS_MODULE, 291 .of_match_table = of_gpio_leds_match, 292 }, 293 }; 294 295 MODULE_ALIAS("platform:leds-gpio"); 296 297 static int __init gpio_led_init(void) 298 { 299 printk(KERN_ERR"zbzhuang leds"); 300 301 302 return platform_driver_register(&gpio_led_driver); 303 } 304 305 static void __exit gpio_led_exit(void) 306 { 307 platform_driver_unregister(&gpio_led_driver); 308 } 309 310 module_init(gpio_led_init); 311 module_exit(gpio_led_exit); 312 313 MODULE_AUTHOR("Raphael Assenat <raph@8d.com>, Trent Piepho <tpiepho@freescale.com>"); 314 MODULE_DESCRIPTION("GPIO LED driver"); 315 MODULE_LICENSE("GPL");
驅動檔案就是根據名字跟 裝置進行匹配。匹配成功之後就會在建立sys檔案系統提供介面給應用程式控制裝置。
在核心執行make menuconfig，要配置LED驅動的一些功能如閃爍和呼吸燈等功能，編譯進核心。
重新燒錄開發板的核心。之後通過串列埠進入開發板。在/sys/class/leds目錄下建立出了，我們板級檔案下新增的4個LED驅動。
下面我們演示如何通過sys檔案系統控制LED的亮滅。進入connect目錄。執行下面三條命令就可控制LED燈的亮滅和進入呼吸燈的模式。
