Linux红外驱动重点解析
初次接触Linux内核，好仔细阅读顶层目录的readme文件，它是Linux内核的概述和编译命令说明。readme的说明侧重于X86等通用的平台，对于某些特殊的体系结构，可能有些特殊的说明。红外遥控是我们经常见到的一种无线收发设备，比如电视遥控，空调遥控，现在电视遥控有些慢慢变成了蓝牙装置。昨天是在知识星球里面看到有人提问，今天来解析一份网友写的驱动程序。
调试红外需要注意几个细节
1、我们发射的遥控器用肉眼是看不到的，需要拿相机来观察。
2、红外接收管和普通的二极管不同，如果用错物料也是不行的。
1.NEC协议无线传输数据原理
NEC协议的特征：
1、8位地址和8位指令长度；
2、地址和命令两次传输；（确保可靠性）
3、PWM脉冲宽度调制，以发射红外载波的占空比代表“0”和“1”；
4、载波频率为38KHz
5、位时间为1.125ms和2.25ms
NEC码位的定义：一个脉冲对应560us的连续载波，一个逻辑1传输需要2.25ms（560us脉冲+1680us低电平），一个逻辑0的 传输需要1.125ms（560us脉冲+560us低电平）。
而遥控接收头在收到脉冲时为低电平，在没有收到脉冲时为高电平，因此， 我们在接收头端收到的信号为：逻辑1应该是560us低+1680us高，逻辑0应该是560us低+560us高。
如下图：
硬件
2. Linux下的驱动接收程序
参考原文：
https://blog.csdn.net/wllw7176/article/details/110506677
两个驱动文件
[*]gpio-ir-recv.c
[*]/* Copyright (c) 2012, Code Aurora Forum. All rights reserved.
[*] *
[*] * This program is free software; you can redistribute it and/or modify
[*] * it under the terms of the GNU General Public License version 2 and
[*] * only version 2 as published by the Free Software Foundation.
[*] *
[*] * This program is distributed in the hope that it will be useful,
[*] * but WITHOUT ANY WARRANTY; without even the implied warranty of
[*] * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
[*] * GNU General Public License for more details.
[*] */
[*]#include <linux/kernel.h>
[*]#include <linux/init.h>
[*]#include <linux/module.h>
[*]#include <linux/interrupt.h>
[*]#include <linux/gpio.h>
[*]#include <linux/slab.h>
[*]#include <linux/of.h>
[*]#include <linux/of_gpio.h>
[*]#include <linux/platform_device.h>
[*]#include <linux/irq.h>
[*]#include <media/rc-core.h>
[*]#include <media/gpio-ir-recv.h>
[*]#define GPIO_IR_DRIVER_NAME "gpio-rc-recv"
[*]#define GPIO_IR_DEVICE_NAME "gpio_ir_recv"
[*]struct gpio_rc_dev {
[*] struct rc_dev *rcdev;
[*] int gpio_nr;
[*] bool active_low;
[*]};
[*]#ifdef CONFIG_OF
[*]/*
[*] * Translate OpenFirmware node properties into platform_data
[*] */
[*]static int gpio_ir_recv_get_devtree_pdata(struct device *dev,
[*] struct gpio_ir_recv_platform_data *pdata)
[*]{
[*] struct device_node *np = dev->of_node;
[*] enum of_gpio_flags flags;
[*] int gpio;
[*] gpio = of_get_gpio_flags(np, 0, &flags);
[*] if (gpio < 0) {
[*]if (gpio != -EPROBE_DEFER)
[*] dev_err(dev, "Failed to get gpio flags (%d)\n", gpio);
[*]return gpio;
[*] }
[*] pdata->gpiogpio_nr = gpio;
[*] pdata->active_low = (flags & OF_GPIO_ACTIVE_LOW);
[*] /* probe() takes care of map_name == NULL or allowed_protos == 0 */
[*] pdata->map_name = of_get_property(np, "linux,rc-map-name", NULL);
[*] pdata->allowed_protos = 0;
[*] return 0;
[*]}
[*]static const struct of_device_id gpio_ir_recv_of_match[] = {
[*] { .compatible = "gpio-ir-receiver", },
[*] { },
[*]};
[*]MODULE_DEVICE_TABLE(of, gpio_ir_recv_of_match);
[*]#else /* !CONFIG_OF */
[*]#define gpio_ir_recv_get_devtree_pdata(dev, pdata) (-ENOSYS)
[*]#endif
[*]static irqreturn_t gpio_ir_recv_irq(int irq, void *dev_id)
[*]{
[*] struct gpio_rc_dev *gpio_dev = dev_id;
[*] int gval;
[*] int rc = 0;
[*] enum raw_event_type type = IR_SPACE;
[*] gval = gpio_get_value(gpio_dev->gpio_nr);
[*] if (gval < 0)
[*]goto err_get_value;
[*] if (gpio_dev->active_low)
[*]gval = !gval;
[*] if (gval == 1)
[*]type = IR_PULSE;
[*] rc = ir_raw_event_store_edge(gpio_dev->rcdev, type);
[*] if (rc < 0)
[*]goto err_get_value;
[*] ir_raw_event_handle(gpio_dev->rcdev);
[*]err_get_value:
[*] return IRQ_HANDLED;
[*]}
[*]static int gpio_ir_recv_probe(struct platform_device *pdev)
[*]{
[*] struct gpio_rc_dev *gpio_dev;
[*] struct rc_dev *rcdev;
[*] const struct gpio_ir_recv_platform_data *pdata =
[*] pdev->dev.platform_data;
[*] int rc;
[*] if (pdev->dev.of_node) {
[*]struct gpio_ir_recv_platform_data *dtpdata =
[*] devm_kzalloc(&pdev->dev, sizeof(*dtpdata), GFP_KERNEL);
[*]if (!dtpdata)
[*] return -ENOMEM;
[*]rc = gpio_ir_recv_get_devtree_pdata(&pdev->dev, dtpdata);
[*]if (rc)
[*] return rc;
[*]pdata = dtpdata;
[*] }
[*] if (!pdata)
[*]return -EINVAL;
[*] if (pdata->gpio_nr < 0)
[*]return -EINVAL;
[*] gpio_dev = kzalloc(sizeof(struct gpio_rc_dev), GFP_KERNEL);
[*] if (!gpio_dev)
[*]return -ENOMEM;
[*] rcdev = rc_allocate_device();
[*] if (!rcdev) {
[*]rc = -ENOMEM;
[*]goto err_allocate_device;
[*] }
[*] rcdev->priv = gpio_dev;
[*] rcdev->driver_type = RC_DRIVER_IR_RAW;
[*] rcdev->input_name = GPIO_IR_DEVICE_NAME;
[*] rcdev->input_phys = GPIO_IR_DEVICE_NAME "/input0";
[*] rcdev->input_id.bustype = BUS_HOST;
[*] rcdev->input_id.vendor = 0x0001;
[*] rcdev->input_id.product = 0x0001;
[*] rcdev->input_id.version = 0x0100;
[*] rcdev->dev.parent = &pdev->dev;
[*] rcdev->driver_name = GPIO_IR_DRIVER_NAME;
[*] if (pdata->allowed_protos)
[*]rcdev->allowed_protocols = pdata->allowed_protos;
[*] else
[*]rcdev->allowed_protocols = RC_BIT_ALL;
[*] rcdev->map_name = pdata->map_name ?: RC_MAP_EMPTY;
[*] gpio_dev->rcdevrcdev = rcdev;
[*] gpio_dev->gpio_nr = pdata->gpio_nr;
[*] gpio_dev->active_low = pdata->active_low;
[*] rc = gpio_request(pdata->gpio_nr, "gpio-ir-recv");
[*] if (rc < 0)
[*]goto err_gpio_request;
[*] rc= gpio_direction_input(pdata->gpio_nr);
[*] if (rc < 0)
[*]goto err_gpio_direction_input;
[*] rc = rc_register_device(rcdev);
[*] if (rc < 0) {
[*]dev_err(&pdev->dev, "failed to register rc device\n");
[*]goto err_register_rc_device;
[*] }
[*] platform_set_drvdata(pdev, gpio_dev);
[*] rc = request_any_context_irq(gpio_to_irq(pdata->gpio_nr),
[*] gpio_ir_recv_irq,
[*] IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING,
[*] "gpio-ir-recv-irq", gpio_dev);
[*] if (rc < 0)
[*]goto err_request_irq;
[*] return 0;
[*]err_request_irq:
[*] rc_unregister_device(rcdev);
[*] rcdev = NULL;
[*]err_register_rc_device:
[*]err_gpio_direction_input:
[*] gpio_free(pdata->gpio_nr);
[*]err_gpio_request:
[*] rc_free_device(rcdev);
[*]err_allocate_device:
[*] kfree(gpio_dev);
[*] return rc;
[*]}
[*]static int gpio_ir_recv_remove(struct platform_device *pdev)
[*]{
[*] struct gpio_rc_dev *gpio_dev = platform_get_drvdata(pdev);
[*] free_irq(gpio_to_irq(gpio_dev->gpio_nr), gpio_dev);
[*] rc_unregister_device(gpio_dev->rcdev);
[*] gpio_free(gpio_dev->gpio_nr);
[*] kfree(gpio_dev);
[*] return 0;
[*]}
[*]#ifdef CONFIG_PM
[*]static int gpio_ir_recv_suspend(struct device *dev)
[*]{
[*] struct platform_device *pdev = to_platform_device(dev);
[*] struct gpio_rc_dev *gpio_dev = platform_get_drvdata(pdev);
[*] if (device_may_wakeup(dev))
[*]enable_irq_wake(gpio_to_irq(gpio_dev->gpio_nr));
[*] else
[*]disable_irq(gpio_to_irq(gpio_dev->gpio_nr));
[*] return 0;
[*]}
[*]static int gpio_ir_recv_resume(struct device *dev)
[*]{
[*] struct platform_device *pdev = to_platform_device(dev);
[*] struct gpio_rc_dev *gpio_dev = platform_get_drvdata(pdev);
[*] if (device_may_wakeup(dev))
[*]disable_irq_wake(gpio_to_irq(gpio_dev->gpio_nr));
[*] else
[*]enable_irq(gpio_to_irq(gpio_dev->gpio_nr));
[*] return 0;
[*]}
[*]static const struct dev_pm_ops gpio_ir_recv_pm_ops = {
[*] .suspend = gpio_ir_recv_suspend,
[*] .resume = gpio_ir_recv_resume,
[*]};
[*]#endif
[*]static struct platform_driver gpio_ir_recv_driver = {
[*] .probe= gpio_ir_recv_probe,
[*] .remove = gpio_ir_recv_remove,
[*] .driver = {
[*].name = GPIO_IR_DRIVER_NAME,
[*].of_match_table = of_match_ptr(gpio_ir_recv_of_match),
[*]#ifdef CONFIG_PM
[*].pm = &gpio_ir_recv_pm_ops,
[*]#endif
[*] },
[*]};
[*]module_platform_driver(gpio_ir_recv_driver);
[*]MODULE_DESCRIPTION("GPIO IR Receiver driver");
[*]MODULE_LICENSE("GPL v2");
ir-nec-decoder.c
[*]/* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
[*] *
[*] * Copyright (C) 2010 by Mauro Carvalho Chehab
[*] *
[*] * This program is free software; you can redistribute it and/or modify
[*] *it under the terms of the GNU General Public License as published by
[*] *the Free Software Foundation version 2 of the License.
[*] *
[*] *This program is distributed in the hope that it will be useful,
[*] *but WITHOUT ANY WARRANTY; without even the implied warranty of
[*] *MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
[*] *GNU General Public License for more details.
[*] */
[*]#include <linux/bitrev.h>
[*]#include <linux/module.h>
[*]#include "rc-core-priv.h"
[*]#define NEC_NBITS32
[*]#define NEC_UNIT562500/* ns */
[*]#define NEC_HEADER_PULSE (16 * NEC_UNIT)
[*]#define NECX_HEADER_PULSE (8* NEC_UNIT) /* Less common NEC variant */
[*]#define NEC_HEADER_SPACE (8* NEC_UNIT)
[*]#define NEC_REPEAT_SPACE (4* NEC_UNIT)
[*]#define NEC_BIT_PULSE(1* NEC_UNIT)
[*]#define NEC_BIT_0_SPACE(1* NEC_UNIT)
[*]#define NEC_BIT_1_SPACE(3* NEC_UNIT)
[*]#define NEC_TRAILER_PULSE (1* NEC_UNIT)
[*]#define NEC_TRAILER_SPACE (10 * NEC_UNIT) /* even longer in reality */
[*]#define NECX_REPEAT_BITS 1
[*]enum nec_state {
[*] STATE_INACTIVE,
[*] STATE_HEADER_SPACE,
[*] STATE_BIT_PULSE,
[*] STATE_BIT_SPACE,
[*] STATE_TRAILER_PULSE,
[*] STATE_TRAILER_SPACE,
[*]};
[*]/**
[*] * ir_nec_decode() - Decode one NEC pulse or space
[*] * @dev: the struct rc_dev descriptor of the device
[*] * @duration: the struct ir_raw_event descriptor of the pulse/space
[*] *
[*] * This function returns -EINVAL if the pulse violates the state machine
[*] */
[*]static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
[*]{
[*] struct nec_dec *data = &dev->raw->nec;
[*] u32 scancode;
[*] u8 address, not_address, command, not_command;
[*] bool send_32bits = false;
[*] if (!(dev->enabled_protocols & RC_BIT_NEC))
[*]return 0;
[*] if (!is_timing_event(ev)) {
[*]if (ev.reset)
[*] data->state = STATE_INACTIVE;
[*]return 0;
[*] }
[*] IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
[*] data->state, TO_US(ev.duration), TO_STR(ev.pulse));
[*] switch (data->state) {
[*] case STATE_INACTIVE:
[*]if (!ev.pulse)
[*] break;
[*]if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {
[*] data->is_nec_x = false;
[*] data->necx_repeat = false;
[*]} else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
[*] data->is_nec_x = true;
[*]else
[*] break;
[*]data->count = 0;
[*]data->state = STATE_HEADER_SPACE;
[*]return 0;
[*] case STATE_HEADER_SPACE:
[*]if (ev.pulse)
[*] break;
[*]if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
[*] data->state = STATE_BIT_PULSE;
[*] return 0;
[*]} else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
[*] if (!dev->keypressed) {
[*] IR_dprintk(1, "Discarding last key repeat: event after key up\n");
[*] } else {
[*] rc_repeat(dev);
[*] IR_dprintk(1, "Repeat last key\n");
[*] data->state = STATE_TRAILER_PULSE;
[*] }
[*] return 0;
[*]}
[*]break;
[*] case STATE_BIT_PULSE:
[*]if (!ev.pulse)
[*] break;
[*]if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
[*] break;
[*]data->state = STATE_BIT_SPACE;
[*]return 0;
[*] case STATE_BIT_SPACE:
[*]if (ev.pulse)
[*] break;
[*]if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
[*] geq_margin(ev.duration,
[*] NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
[*] IR_dprintk(1, "Repeat last key\n");
[*] rc_repeat(dev);
[*] data->state = STATE_INACTIVE;
[*] return 0;
[*]} else if (data->count > NECX_REPEAT_BITS)
[*] data->necx_repeat = false;
[*]data->bits <<= 1;
[*]if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2)
[*] data->bits |= 1;
[*]else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
[*] break;
[*]data->count++;
[*]if (data->count == NEC_NBITS)
[*] data->state = STATE_TRAILER_PULSE;
[*]else
[*] data->state = STATE_BIT_PULSE;
[*]return 0;
[*] case STATE_TRAILER_PULSE:
[*]if (!ev.pulse)
[*] break;
[*]if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
[*] break;
[*]data->state = STATE_TRAILER_SPACE;
[*]return 0;
[*] case STATE_TRAILER_SPACE:
[*]if (ev.pulse)
[*] break;
[*]if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
[*] break;
[*]address = bitrev8((data->bits >> 24) & 0xff);
[*]not_address = bitrev8((data->bits >> 16) & 0xff);
[*]command = bitrev8((data->bits >>8) & 0xff);
[*]not_command = bitrev8((data->bits >>0) & 0xff);
[*]if ((command ^ not_command) != 0xff) {
[*] IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
[*] data->bits);
[*] send_32bits = true;
[*]}
[*]if (send_32bits) {
[*] /* NEC transport, but modified protocol, used by at
[*] * least Apple and TiVo remotes */
[*] scancode = data->bits;
[*] IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode);
[*]} else if ((address ^ not_address) != 0xff) {
[*] /* Extended NEC */
[*] scancode = address << 16 |
[*] not_address <<8 |
[*] command;
[*] IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
[*]} else {
[*] /* Normal NEC */
[*] scancode = address << 8 | command;
[*] IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
[*]}
[*]if (data->is_nec_x)
[*] data->necx_repeat = true;
[*]rc_keydown(dev, RC_TYPE_NEC, scancode, 0);
[*]data->state = STATE_INACTIVE;
[*]return 0;
[*] }
[*] IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
[*] data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
[*] data->state = STATE_INACTIVE;
[*] return -EINVAL;
[*]}
[*]static struct ir_raw_handler nec_handler = {
[*] .protocols = RC_BIT_NEC,
[*] .decode= ir_nec_decode,
[*]};
[*]static int __init ir_nec_decode_init(void)
[*]{
[*] ir_raw_handler_register(&nec_handler);
[*] printk(KERN_INFO "IR NEC protocol handler initialized\n");
[*] return 0;
[*]}
[*]static void __exit ir_nec_decode_exit(void)
[*]{
[*] ir_raw_handler_unregister(&nec_handler);
[*]}
[*]module_init(ir_nec_decode_init);
[*]module_exit(ir_nec_decode_exit);
[*]MODULE_LICENSE("GPL");
[*]MODULE_AUTHOR("Mauro Carvalho Chehab");
[*]MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
[*]MODULE_DESCRIPTION("NEC IR protocol decoder");
参考文章中的dts文件：
[*]gpio-ir-receiver {
[*] compatible = "gpio-ir-receiver";
[*] gpios = <&gpio4 19 GPIO_ACTIVE_HIGH>; //连接红外的中断引脚
[*] active_low = <1>; //红外接收器是否将信号取反，有些红外接收器会将接收到的高低电平信号反向输出，比如我使用的hx1838红外接收器
[*] linux,rc-map-name = "rc-hx18380-carmp3"; //红外scancode与实际input_evnent code映射表名称，要在rc_register_device注册，具体见gpio-ir-recv.c
[*] allowed_protos = <0x100>; /*NEC protocol*/ //保留，驱动中并未使用
[*]};
另一个文件里面调用的
ir-nec-decoder.c
这个函数是Linux内核中的红外处理申请函数
这里主要是注册一个解码的结构体
ir-nec-decoder.c
3.中断处理程序解析
gpio-ir-recv.c
ir_raw_event_store_edge（） 这个函数用来计算电平的持续时间。
ir_raw_event_handle（） 用来处理这个电平表示什么含义。
驱动程序里面，首先是判断当前GPIO电平，如果是低电平，就进入红外解析，如果不是，或者获取失败，就退出程序。
4.红外数据处理程序解析
内核专门开了一个线程来处理数据解析
rc-ir-raw.c
处理函数其实就是处理电平时间长短来决定数字信号
ir-nec-decoder.c
这里是判断头，这个时间和9ms进行比较
9ms 从哪里来的,可以看看这里
ir-nec-decoder.c
拿到头后，这个switch函数就继续往下跑
ir-nec-decoder.c
然后就是判断 1 和 0的时候了
ir-nec-decoder.c
上面那个就是1，下面那个就是0。
4.然后数据怎么上报呢？
ir-nec-decoder.c
这里是在另一个模块中注册的映射
不同的红外键值对应不同的上报按键键值
rc-trekstor.c
原文链接：https://mp.weixin.qq.com/s/mwjY69oSF8WjnZ2B8a8Xeg
http://www.zzvips.com/article/165392.html
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