在线时间410 小时
UID3006061
注册时间2015-3-23
NXP金币1309
TA的每日心情 | 开心 4 天前 |
---|
签到天数: 822 天 [LV.10]以坛为家III
金牌会员
- 积分
- 5531
- 最后登录
- 2024-5-1
|
本帖最后由 leo121_3006061 于 2018-7-6 12:10 编辑
上一篇帖子有个分析的led的example的帖子,不是十分全面,只是从devicetree的角度,当时还不是十分理解,经过一段时间的学习,终于明白,还需要有个led的driver配合才能在/sys/class/目录下出现leds,简要的说就是先在devicetree中分配好资源,然后再从为之写一个驱动程序,这时候就会出现在/sys/class/leds。当然驱动程序不是必须要写的,example中gpio_keys操作就没有写驱动,当然在/sys/class/目录下也见不到。下边我们通过三种不同的方式来理解一下gpio的驱动。
1. 我们先打开目录,如下图所示,并且找到led_gpio.c(目录下还有pwm等其他的驱动)
led的驱动源代码如下
- /*
- * LEDs driver for GPIOs
- *
- * Copyright (C) 2007 8D Technologies inc.
- * Raphael Assenat <raph@8d.com>
- * Copyright (C) 2008 Freescale Semiconductor, Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- */
- #include <linux/err.h>
- #include <linux/gpio.h>
- #include <linux/gpio/consumer.h>
- #include <linux/kernel.h>
- #include <linux/leds.h>
- #include <linux/module.h>
- #include <linux/platform_device.h>
- #include <linux/property.h>
- #include <linux/slab.h>
- #include <linux/workqueue.h>
- struct gpio_led_data {
- struct led_classdev cdev;
- struct gpio_desc *gpiod;
- struct work_struct work;
- u8 new_level;
- u8 can_sleep;
- u8 blinking;
- int (*platform_gpio_blink_set)(struct gpio_desc *desc, int state,
- unsigned long *delay_on, unsigned long *delay_off);
- };
- static void gpio_led_work(struct work_struct *work)
- {
- struct gpio_led_data *led_dat =
- container_of(work, struct gpio_led_data, work);
- if (led_dat->blinking) {
- led_dat->platform_gpio_blink_set(led_dat->gpiod,
- led_dat->new_level, NULL, NULL);
- led_dat->blinking = 0;
- } else
- gpiod_set_value_cansleep(led_dat->gpiod, led_dat->new_level);
- }
- static void gpio_led_set(struct led_classdev *led_cdev,
- enum led_brightness value)
- {
- struct gpio_led_data *led_dat =
- container_of(led_cdev, struct gpio_led_data, cdev);
- int level;
- if (value == LED_OFF)
- level = 0;
- else
- level = 1;
- /* Setting GPIOs with I2C/etc requires a task context, and we don't
- * seem to have a reliable way to know if we're already in one; so
- * let's just assume the worst.
- */
- if (led_dat->can_sleep) {
- led_dat->new_level = level;
- schedule_work(&led_dat->work);
- } else {
- if (led_dat->blinking) {
- led_dat->platform_gpio_blink_set(led_dat->gpiod, level,
- NULL, NULL);
- led_dat->blinking = 0;
- } else
- gpiod_set_value(led_dat->gpiod, level);
- }
- }
- static int gpio_blink_set(struct led_classdev *led_cdev,
- unsigned long *delay_on, unsigned long *delay_off)
- {
- struct gpio_led_data *led_dat =
- container_of(led_cdev, struct gpio_led_data, cdev);
- led_dat->blinking = 1;
- return led_dat->platform_gpio_blink_set(led_dat->gpiod, GPIO_LED_BLINK,
- delay_on, delay_off);
- }
- static int create_gpio_led(const struct gpio_led *template,
- struct gpio_led_data *led_dat, struct device *parent,
- int (*blink_set)(struct gpio_desc *, int, unsigned long *,
- unsigned long *))
- {
- int ret, state;
- led_dat->gpiod = template->gpiod;
- if (!led_dat->gpiod) {
- /*
- * This is the legacy code path for platform code that
- * still uses GPIO numbers. Ultimately we would like to get
- * rid of this block completely.
- */
- unsigned long flags = 0;
- /* skip leds that aren't available */
- if (!gpio_is_valid(template->gpio)) {
- dev_info(parent, "Skipping unavailable LED gpio %d (%s)\n",
- template->gpio, template->name);
- return 0;
- }
- if (template->active_low)
- flags |= GPIOF_ACTIVE_LOW;
- ret = devm_gpio_request_one(parent, template->gpio, flags,
- template->name);
- if (ret < 0)
- return ret;
- led_dat->gpiod = gpio_to_desc(template->gpio);
- if (IS_ERR(led_dat->gpiod))
- return PTR_ERR(led_dat->gpiod);
- }
- led_dat->cdev.name = template->name;
- led_dat->cdev.default_trigger = template->default_trigger;
- led_dat->can_sleep = gpiod_cansleep(led_dat->gpiod);
- led_dat->blinking = 0;
- if (blink_set) {
- led_dat->platform_gpio_blink_set = blink_set;
- led_dat->cdev.blink_set = gpio_blink_set;
- }
- led_dat->cdev.brightness_set = gpio_led_set;
- if (template->default_state == LEDS_GPIO_DEFSTATE_KEEP)
- state = !!gpiod_get_value_cansleep(led_dat->gpiod);
- else
- state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
- led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;
- if (!template->retain_state_suspended)
- led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
- ret = gpiod_direction_output(led_dat->gpiod, state);
- if (ret < 0)
- return ret;
- INIT_WORK(&led_dat->work, gpio_led_work);
- return led_classdev_register(parent, &led_dat->cdev);
- }
- static void delete_gpio_led(struct gpio_led_data *led)
- {
- led_classdev_unregister(&led->cdev);
- cancel_work_sync(&led->work);
- }
- struct gpio_leds_priv {
- int num_leds;
- struct gpio_led_data leds[];
- };
- static inline int sizeof_gpio_leds_priv(int num_leds)
- {
- return sizeof(struct gpio_leds_priv) +
- (sizeof(struct gpio_led_data) * num_leds);
- }
- static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)
- {
- struct device *dev = &pdev->dev;
- struct fwnode_handle *child;
- struct gpio_leds_priv *priv;
- int count, ret;
- struct device_node *np;
- count = device_get_child_node_count(dev);
- if (!count)
- return ERR_PTR(-ENODEV);
- priv = devm_kzalloc(dev, sizeof_gpio_leds_priv(count), GFP_KERNEL);
- if (!priv)
- return ERR_PTR(-ENOMEM);
- device_for_each_child_node(dev, child) {
- struct gpio_led led = {};
- const char *state = NULL;
- led.gpiod = devm_get_gpiod_from_child(dev, NULL, child);
- if (IS_ERR(led.gpiod)) {
- fwnode_handle_put(child);
- ret = PTR_ERR(led.gpiod);
- goto err;
- }
- np = of_node(child);
- if (fwnode_property_present(child, "label")) {
- fwnode_property_read_string(child, "label", &led.name);
- } else {
- if (IS_ENABLED(CONFIG_OF) && !led.name && np)
- led.name = np->name;
- if (!led.name)
- return ERR_PTR(-EINVAL);
- }
- fwnode_property_read_string(child, "linux,default-trigger",
- &led.default_trigger);
- if (!fwnode_property_read_string(child, "default-state",
- &state)) {
- if (!strcmp(state, "keep"))
- led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
- else if (!strcmp(state, "on"))
- led.default_state = LEDS_GPIO_DEFSTATE_ON;
- else
- led.default_state = LEDS_GPIO_DEFSTATE_OFF;
- }
- if (fwnode_property_present(child, "retain-state-suspended"))
- led.retain_state_suspended = 1;
- ret = create_gpio_led(&led, &priv->leds[priv->num_leds++],
- dev, NULL);
- if (ret < 0) {
- fwnode_handle_put(child);
- goto err;
- }
- }
- return priv;
- err:
- for (count = priv->num_leds - 2; count >= 0; count--)
- delete_gpio_led(&priv->leds[count]);
- return ERR_PTR(ret);
- }
- static const struct of_device_id of_gpio_leds_match[] = {
- { .compatible = "gpio-leds", },
- {},
- };
- MODULE_DEVICE_TABLE(of, of_gpio_leds_match);
- static int gpio_led_probe(struct platform_device *pdev)
- {
- struct gpio_led_platform_data *pdata = dev_get_platdata(&pdev->dev);
- struct gpio_leds_priv *priv;
- int i, ret = 0;
- if (pdata && pdata->num_leds) {
- priv = devm_kzalloc(&pdev->dev,
- sizeof_gpio_leds_priv(pdata->num_leds),
- GFP_KERNEL);
- if (!priv)
- return -ENOMEM;
- priv->num_leds = pdata->num_leds;
- for (i = 0; i < priv->num_leds; i++) {
- ret = create_gpio_led(&pdata->leds[i],
- &priv->leds[i],
- &pdev->dev, pdata->gpio_blink_set);
- if (ret < 0) {
- /* On failure: unwind the led creations */
- for (i = i - 1; i >= 0; i--)
- delete_gpio_led(&priv->leds[i]);
- return ret;
- }
- }
- } else {
- priv = gpio_leds_create(pdev);
- if (IS_ERR(priv))
- return PTR_ERR(priv);
- }
- platform_set_drvdata(pdev, priv);
- return 0;
- }
- static int gpio_led_remove(struct platform_device *pdev)
- {
- struct gpio_leds_priv *priv = platform_get_drvdata(pdev);
- int i;
- for (i = 0; i < priv->num_leds; i++)
- delete_gpio_led(&priv->leds[i]);
- return 0;
- }
- static struct platform_driver gpio_led_driver = {
- .probe = gpio_led_probe,
- .remove = gpio_led_remove,
- .driver = {
- .name = "leds-gpio",
- .of_match_table = of_gpio_leds_match,
- },
- };
- module_platform_driver(gpio_led_driver);
- MODULE_AUTHOR("Raphael Assenat <raph@8d.com>, Trent Piepho <tpiepho@freescale.com>");
- MODULE_DESCRIPTION("GPIO LED driver");
- MODULE_LICENSE("GPL");
- MODULE_ALIAS("platform:leds-gpio");
复制代码 从上边的源程序里我们找到一些相关的信息,brightness等,这就明白了,/sys/class/leds/目录下和/sys/firmware/devicetree/base/leds目录下的内容为何不同了,说的明白一点就是这两个目录是分别由drivers和devicetree生成的。从而也就解开了心中的谜团。
2. 第一步的这种写法虽然比较规范,但有些过于复杂,适合lcd之类的驱动,其实简单的驱动例如gpio_key并不需要专门再写个驱动的,这样就比较灵活了,也可以简单的使用echo命令直接驱动gpio
echo 9 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio9/direction
echo 1 > /sys/class/gpio/gpio9/value ---> 写高电平
echo 0 > /sys/class/gpio/gpio9/value ---> 写低电平
通过这种方式直接可以简单的操控gpio,非常的灵活。
3. 也可以通过程序来直接读取和操作gpio,不过者和第2步一样,都是必须在编译内核的时候要加入gpio support才行,也就是说在/sys/class/目录下有个gpio目录才行。我从网上找了一个例程供参考,如下
- #include stdlib.h
- #include stdio.h
- #include string.h
- #include unistd.h
- #include fcntl.h //define O_WRONLY and O_RDONLY
- //芯片复位引脚: P1_16
- #define SYSFS_GPIO_EXPORT "/sys/class/gpio/export"
- #define SYSFS_GPIO_RST_PIN_VAL "48"
- #define SYSFS_GPIO_RST_DIR "/sys/class/gpio/gpio48/direction"
- #define SYSFS_GPIO_RST_DIR_VAL "OUT"
- #define SYSFS_GPIO_RST_VAL "/sys/class/gpio/gpio48/value"
- #define SYSFS_GPIO_RST_VAL_H "1"
- #define SYSFS_GPIO_RST_VAL_L "0"
- int main()
- {
- int fd;
- //打开端口/sys/class/gpio# echo 48 > export
- fd = open(SYSFS_GPIO_EXPORT, O_WRONLY);
- if(fd == -1)
- {
- printf("ERR: Radio hard reset pin open error.\n");
- return EXIT_FAILURE;
- }
- write(fd, SYSFS_GPIO_RST_PIN_VAL ,sizeof(SYSFS_GPIO_RST_PIN_VAL));
- close(fd);
- //设置端口方向/sys/class/gpio/gpio48# echo out > direction
- fd = open(SYSFS_GPIO_RST_DIR, O_WRONLY);
- if(fd == -1)
- {
- printf("ERR: Radio hard reset pin direction open error.\n");
- return EXIT_FAILURE;
- }
- write(fd, SYSFS_GPIO_RST_DIR_VAL, sizeof(SYSFS_GPIO_RST_DIR_VAL));
- close(fd);
- //输出复位信号: 拉高>100ns
- fd = open(SYSFS_GPIO_RST_VAL, O_RDWR);
- if(fd == -1)
- {
- printf("ERR: Radio hard reset pin value open error.\n");
- return EXIT_FAILURE;
- }
- while(1)
- {
- write(fd, SYSFS_GPIO_RST_VAL_H, sizeof(SYSFS_GPIO_RST_VAL_H));
- usleep(1000000);
- write(fd, SYSFS_GPIO_RST_VAL_L, sizeof(SYSFS_GPIO_RST_VAL_L));
- usleep(1000000);
- }
- close(fd);
- printf("INFO: Radio hard reset pin value open error.\n");
- return 0;
- }
复制代码 【综述】通过上边gpio灵活多样的操作,并不局限于某种方式,在我没有理解devicetree和driver区别之前还是有些懵的,至少在我写完这篇之后,感觉又进一层了解了嵌入式开发的原理。
|
|