6.misc类设备与蜂鸣器驱动

转自 https://edu.csdn.net/lecturer/505 朱老师物联网大讲堂
《5.linux驱动开发-第6部分-5.6.misc类设备与蜂鸣器驱动》

第一部分、章节目录
5.6.1.板载蜂鸣器驱动测试
5.6.2.misc类设备介绍
5.6.3.misc驱动框架源码分析1
5.6.4.misc驱动框架源码分析2
5.6.5.蜂鸣器驱动源码分析1
5.6.6.蜂鸣器驱动源码分析2

第二部分、章节介绍
5.6.1.板载蜂鸣器驱动测试
本节使用内核中提供的蜂鸣器驱动来实践测试蜂鸣器，要同时解决驱动层的问题和应用程序的编写。
5.6.2.misc类设备介绍
本节系统介绍misc类设备的概念和分类特点，并且对misc类设备的驱动框架详细讲解。
5.6.3.misc驱动框架源码分析1
本节分析misc类设备驱动框架中内核自己实现的部分，即misc.c。
5.6.4.misc驱动框架源码分析2
本节继续分析misc.c，重点是信号量及其使用的一般技巧。
5.6.5.蜂鸣器驱动源码分析1
本节分析九鼎提供的buzzer驱动源码
5.6.6.蜂鸣器驱动源码分析2
本节分析九鼎提供的buzzer驱动源码

第三部分、随堂记录
5.6.1.板载蜂鸣器驱动测试
5.6.1.1、驱动部分
(1)九鼎移植内核已经提供了蜂鸣器驱动源码
(2)make menuconfig
(3)bug排查。修改Makefile中的宏名，最终可以在系统中看到 /dev/buzzer
5.6.1.2、应用部分
(1)应用编写：打开文件+ioctl
(2)测试实践

#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>


#define DEVNAME		"/dev/buzzer"

#define PWM_IOCTL_SET_FREQ		1
#define PWM_IOCTL_STOP			0


int main(void)
{
	int fd = -1;
	
	fd = open(DEVNAME, O_RDWR);
	if (fd < 0)
	{
		perror("open");
		return -1;
	}
	
	ioctl(fd, PWM_IOCTL_SET_FREQ, 10000);
	sleep(3);
	ioctl(fd, PWM_IOCTL_STOP);
	sleep(3);
	ioctl(fd, PWM_IOCTL_SET_FREQ, 3000);
	sleep(3);
	ioctl(fd, PWM_IOCTL_STOP);
	sleep(3);
	
	
	close(fd);
	
	return 0;
}

5.6.2.misc类设备介绍
5.6.2.1、何为misc
(1)中文名：杂项设备\杂散设备
(2)/sys/class/misc
(3)典型的字符设备
(4)有一套驱动框架，内核实现一部分（misc.c），驱动实现一部分（x210-buzzer.c）。
(5)misc是对原始的字符设备注册接口的一个类层次的封装，很多典型字符设备都可以归类到misc类中，使用misc驱动框架来管理。
5.6.2.2、misc类设备驱动架构
(1)内核开发者实现部分，关键点有2个：一个是类的创建，另一个是开放给驱动开发者的接口
(2)具体设备驱动工程师实现部分
5.6.2.3、本部分学习方法
(1)蜂鸣器驱动源码已有，分析为主
(2)复习并验证前面讲的驱动框架的思维
(3)有余力的不妨开始注意一些细节

5.6.3.misc驱动框架源码分析1
5.6.3.1、misc源码框架基础
(1)misc源码框架本身也是一个模块，内核启动时自动加载
(2)源码框架的主要工作：注册misc类，使用老接口注册字符设备驱动（主设备号10），开放device注册的接口misc_register给驱动工程师
5.6.3.2、misc类设备的注册
(1)驱动工程师需要借助misc来加载自己的驱动时，只需要调用misc_register接口注册自己的设备即可，其余均不用管。
(2)misc_list链表的作用。内核定义了一个misc_list链表用来记录所有内核中注册了的杂散类设备。当我们向内核注册一个misc类设备时，内核就会向misc_list链表中insert一个节点。
#define LIST_HEAD_INIT(name) { &(name), &(name) }
#define LIST_HEAD(name)
struct list_head name = LIST_HEAD_INIT(name)

原式子：static LIST_HEAD(misc_list);
展开后：static struct list_head misc_list = { &(misc_list), &(misc_list) }
(3)主设备号和次设备号的作用和区分

/*
 * linux/drivers/char/misc.c
 *
 * Generic misc open routine by Johan Myreen
 *
 * Based on code from Linus
 *
 * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
 *   changes incorporated into 0.97pl4
 *   by Peter Cervasio (pete%[email protected]) (08SEP92)
 *   See busmouse.c for particulars.
 *
 * Made things a lot mode modular - easy to compile in just one or two
 * of the misc drivers, as they are now completely independent. Linus.
 *
 * Support for loadable modules. 8-Sep-95 Philip Blundell <[email protected]>
 *
 * Fixed a failing symbol register to free the device registration
 *		Alan Cox <[email protected]> 21-Jan-96
 *
 * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
 *
 * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
 *
 * Handling of mouse minor numbers for kerneld:
 *  Idea by Jacques Gelinas <[email protected]>,
 *  adapted by Bjorn Ekwall <[email protected]>
 *  corrected by Alan Cox <[email protected]>
 *
 * Changes for kmod (from kerneld):
 *	Cyrus Durgin <[email protected]>
 *
 * Added devfs support. Richard Gooch <[email protected]>  10-Jan-1998
 */

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>

/*
 * Head entry for the doubly linked miscdevice list
 */
static LIST_HEAD(misc_list);
static DEFINE_MUTEX(misc_mtx);

/*
 * Assigned numbers, used for dynamic minors
 */
#define DYNAMIC_MINORS 64 /* like dynamic majors */
static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);

#ifdef CONFIG_PROC_FS
static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
{
	mutex_lock(&misc_mtx);
	return seq_list_start(&misc_list, *pos);
}

static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	return seq_list_next(v, &misc_list, pos);
}

static void misc_seq_stop(struct seq_file *seq, void *v)
{
	mutex_unlock(&misc_mtx);
}

static int misc_seq_show(struct seq_file *seq, void *v)
{
	const struct miscdevice *p = list_entry(v, struct miscdevice, list);

	seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
	return 0;
}


static const struct seq_operations misc_seq_ops = {
	.start = misc_seq_start,
	.next  = misc_seq_next,
	.stop  = misc_seq_stop,
	.show  = misc_seq_show,
};

static int misc_seq_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &misc_seq_ops);
}

static const struct file_operations misc_proc_fops = {
	.owner	 = THIS_MODULE,
	.open    = misc_seq_open,
	.read    = seq_read,
	.llseek  = seq_lseek,
	.release = seq_release,
};
#endif

static int misc_open(struct inode * inode, struct file * file)
{
	int minor = iminor(inode);
	struct miscdevice *c;
	int err = -ENODEV;
	const struct file_operations *new_fops = NULL;

	mutex_lock(&misc_mtx);

	list_for_each_entry(c, &misc_list, list) {
		if (c->minor == minor) {
			new_fops = fops_get(c->fops);
			break;
		}
	}

	if (!new_fops) {
		mutex_unlock(&misc_mtx);
		request_module("char-major-%d-%d", MISC_MAJOR, minor);
		mutex_lock(&misc_mtx);

		list_for_each_entry(c, &misc_list, list) {
			if (c->minor == minor) {
				new_fops = fops_get(c->fops);
				break;
			}
		}
		if (!new_fops)
			goto fail;
	}

	/*
	 * Place the miscdevice in the file's
	 * private_data so it can be used by the
	 * file operations, including f_op->open below
	 */
	file->private_data = c;

	err = 0;
	replace_fops(file, new_fops);
	if (file->f_op->open)
		err = file->f_op->open(inode,file);
fail:
	mutex_unlock(&misc_mtx);
	return err;
}

static struct class *misc_class;

static const struct file_operations misc_fops = {
	.owner		= THIS_MODULE,
	.open		= misc_open,
	.llseek		= noop_llseek,
};

/**
 *	misc_register	-	register a miscellaneous device
 *	@misc: device structure
 *
 *	Register a miscellaneous device with the kernel. If the minor
 *	number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 *	and placed in the minor field of the structure. For other cases
 *	the minor number requested is used.
 *
 *	The structure passed is linked into the kernel and may not be
 *	destroyed until it has been unregistered. By default, an open()
 *	syscall to the device sets file->private_data to point to the
 *	structure. Drivers don't need open in fops for this.
 *
 *	A zero is returned on success and a negative errno code for
 *	failure.
 */

int misc_register(struct miscdevice * misc)
{
	dev_t dev;
	int err = 0;
	bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);

	INIT_LIST_HEAD(&misc->list);

	mutex_lock(&misc_mtx);

	if (is_dynamic) {
		int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
		if (i >= DYNAMIC_MINORS) {
			err = -EBUSY;
			goto out;
		}
		misc->minor = DYNAMIC_MINORS - i - 1;
		set_bit(i, misc_minors);
	} else {
		struct miscdevice *c;

		list_for_each_entry(c, &misc_list, list) {
			if (c->minor == misc->minor) {
				err = -EBUSY;
				goto out;
			}
		}
	}

	dev = MKDEV(MISC_MAJOR, misc->minor);

	misc->this_device =
		device_create_with_groups(misc_class, misc->parent, dev,
					  misc, misc->groups, "%s", misc->name);
	if (IS_ERR(misc->this_device)) {
		if (is_dynamic) {
			int i = DYNAMIC_MINORS - misc->minor - 1;

			if (i < DYNAMIC_MINORS && i >= 0)
				clear_bit(i, misc_minors);
			misc->minor = MISC_DYNAMIC_MINOR;
		}
		err = PTR_ERR(misc->this_device);
		goto out;
	}

	/*
	 * Add it to the front, so that later devices can "override"
	 * earlier defaults
	 */
	list_add(&misc->list, &misc_list);
 out:
	mutex_unlock(&misc_mtx);
	return err;
}

/**
 *	misc_deregister - unregister a miscellaneous device
 *	@misc: device to unregister
 *
 *	Unregister a miscellaneous device that was previously
 *	successfully registered with misc_register().
 */

void misc_deregister(struct miscdevice *misc)
{
	int i = DYNAMIC_MINORS - misc->minor - 1;

	if (WARN_ON(list_empty(&misc->list)))
		return;

	mutex_lock(&misc_mtx);
	list_del(&misc->list);
	device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
	if (i < DYNAMIC_MINORS && i >= 0)
		clear_bit(i, misc_minors);
	mutex_unlock(&misc_mtx);
}

EXPORT_SYMBOL(misc_register);
EXPORT_SYMBOL(misc_deregister);

static char *misc_devnode(struct device *dev, umode_t *mode)
{
	struct miscdevice *c = dev_get_drvdata(dev);

	if (mode && c->mode)
		*mode = c->mode;
	if (c->nodename)
		return kstrdup(c->nodename, GFP_KERNEL);
	return NULL;
}

static int __init misc_init(void)
{
	int err;
	struct proc_dir_entry *ret;

	ret = proc_create("misc", 0, NULL, &misc_proc_fops);
	misc_class = class_create(THIS_MODULE, "misc");
	err = PTR_ERR(misc_class);
	if (IS_ERR(misc_class))
		goto fail_remove;

	err = -EIO;
	if (register_chrdev(MISC_MAJOR,"misc",&misc_fops))
		goto fail_printk;
	misc_class->devnode = misc_devnode;
	return 0;

fail_printk:
	printk("unable to get major %d for misc devices\n", MISC_MAJOR);
	class_destroy(misc_class);
fail_remove:
	if (ret)
		remove_proc_entry("misc", NULL);
	return err;
}
subsys_initcall(misc_init);

5.6.4.misc驱动框架源码分析2
5.6.4.1、open函数分析
5.6.4.2、misc在proc下的展现
5.6.4.3、内核互斥锁
(1)何为互斥锁
(2)定义：DEFINE_MUTEX
(3)上锁mutex_lock和解锁mutex_unlock
(4)内核防止竞争状态的手段：原子访问、自旋锁、互斥锁、信号量
(5)原子访问主要用来做计数、自旋锁后面讲中断会详细讲、互斥锁和信号量很相似（其实就是计数值为1的信号量），互斥锁的出现比信号量晚，实现上比信号量优秀，尽量使用互斥锁。

5.6.5.蜂鸣器驱动源码分析1
5.6.5.1、dev_init
(1)信号量
(2)miscdevice
(3)gpio_request
(4)printk
5.6.5.2、ioctl
(1)为什么需要ioctl（input output control，输入输出控制）。
(2)ioctl怎么用

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/poll.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <mach/hardware.h>
#include <plat/regs-timer.h>
#include <mach/regs-irq.h>
#include <asm/mach/time.h>
#include <linux/clk.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
 
#include <linux/gpio.h>
 
#include <plat/gpio-cfg.h>
//#include <plat/regs-clock.h>
//#include <plat/regs-gpio.h>
 
//#include <plat/gpio-bank-e.h>
//#include <plat/gpio-bank-f.h>
//#include <plat/gpio-bank-k.h>
 
#define DEVICE_NAME     "buzzer"
 
#define PWM_IOCTL_SET_FREQ     1
#define PWM_IOCTL_STOP         0
 
static struct semaphore lock;	//定义一个信号量
 
// TCFG0在Uboot中设置，这里不再重复设置
// Timer0输入频率Finput=pclk/(prescaler1+1)/MUX1
//                     =66M/16/16
// TCFG0 = tcnt = (pclk/16/16)/freq;
// PWM0输出频率Foutput =Finput/TCFG0= freq
static void PWM_Set_Freq( unsigned long freq )
{
    unsigned long tcon;
    unsigned long tcnt;
    unsigned long tcfg1;
 
    struct clk *clk_p;
    unsigned long pclk;
 
    //unsigned tmp;
     
    //设置GPD0_2为PWM输出
    s3c_gpio_cfgpin(S5PV210_GPD0(2), S3C_GPIO_SFN(2));
 
    tcon = __raw_readl(S3C2410_TCON);
    tcfg1 = __raw_readl(S3C2410_TCFG1);
 
    //mux = 1/16
    tcfg1 &= ~(0xf<<8);
    tcfg1 |= (0x4<<8);
    __raw_writel(tcfg1, S3C2410_TCFG1);
     
    clk_p = clk_get(NULL, "pclk");
    pclk  = clk_get_rate(clk_p);
 
    tcnt  = (pclk/16/16)/freq;
     
    __raw_writel(tcnt, S3C2410_TCNTB(2));
    __raw_writel(tcnt/2, S3C2410_TCMPB(2));//占空比为50%
 
    tcon &= ~(0xf<<12);
    tcon |= (0xb<<12);      //disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 0
    __raw_writel(tcon, S3C2410_TCON);
     
    tcon &= ~(2<<12);           //clear manual update bit
    __raw_writel(tcon, S3C2410_TCON);
}
 
void PWM_Stop( void )
{
    //将GPD0_2设置为input
    s3c_gpio_cfgpin(S5PV210_GPD0(2), S3C_GPIO_SFN(0));
}
 
static int x210_pwm_open(struct inode *inode, struct file *file)
{
    if (!down_trylock(&lock))
        return 0;
    else
        return -EBUSY;
     
}
 
 
static int x210_pwm_close(struct inode *inode, struct file *file)
{
    up(&lock);
    return 0;
}
 
// PWM:GPF14->PWM0
static int x210_pwm_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
    switch (cmd) 
    {
        case PWM_IOCTL_SET_FREQ:
            printk("PWM_IOCTL_SET_FREQ:\r\n");
            if (arg == 0)
                return -EINVAL;
            PWM_Set_Freq(arg);
            break;
 
        case PWM_IOCTL_STOP:
        default:
            printk("PWM_IOCTL_STOP:\r\n");
            PWM_Stop();
            break;
    }
 
    return 0;
}
 
 
static struct file_operations dev_fops = {
    .owner   =   THIS_MODULE,
    .open    =   x210_pwm_open,
    .release =   x210_pwm_close, 
    .ioctl   =   x210_pwm_ioctl,
};
 
static struct miscdevice misc = {
    .minor = MISC_DYNAMIC_MINOR,	//255 系统自动分配次设备号
    .name = DEVICE_NAME,	//设备名字
    .fops = &dev_fops,	//file_operations结构体
};
 
static int __init dev_init(void)
{
    int ret;
 
    init_MUTEX(&lock);	//初始化信号量
    ret = misc_register(&misc);	//内核开放给驱动开发的接口注册misc设备
     
    /* GPD0_2 (PWMTOUT2)对硬件初始化 */
    ret = gpio_request(S5PV210_GPD0(2), "GPD0");	//向内核申请S5PV210_GPD0(2)引脚
    if(ret)
        printk("buzzer-x210: request gpio GPD0(2) fail");
         
    s3c_gpio_setpull(S5PV210_GPD0(2), S3C_GPIO_PULL_UP);	//设置为上拉模式
    s3c_gpio_cfgpin(S5PV210_GPD0(2), S3C_GPIO_SFN(1));	//设置为输出模式
    gpio_set_value(S5PV210_GPD0(2), 0);	//输出值0
 
    printk ("x210 "DEVICE_NAME" initialized\n");	//"内核自动把字符串拼接为一个字符串
        return ret;
}
 
static void __exit dev_exit(void)
{
    misc_deregister(&misc);
}
 
module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("www.9tripod.com");
MODULE_DESCRIPTION("x210 PWM Driver");

5.6.6.蜂鸣器驱动源码分析2
硬件操作有关的代码