基於linux（2.6.32）通用adc接口的簡單測試驅動

1. 在arch/arm/mach-s3c2440/mini2440.c中添加：

static struct platform_device mini2440_adc = {
	.name = "mini2440_adc",
	.id = -1,
	.dev.parent = &s3c_device_adc.dev,
//	.num_resources	  = ARRAY_SIZE(s3c_adc_resource),
//	.resource	  = s3c_adc_resource,
};

static struct platform_device *mini2440_devices[] __initdata = {
	&s3c_device_usb,
	&s3c_device_rtc,
	&s3c_device_lcd,
	&s3c_device_wdt,
	&s3c_device_i2c0,
	&s3c_device_iis,
	&mini2440_device_eth,
	&s3c24xx_uda134x,
	&s3c_device_nand,
	&s3c_device_sdi,
	&s3c_device_usbgadget,
	&s3c_device_adc,		//添加下兩行
	&mini2440_adc,
};

2. 寫自己的驅動

/*===============================================================
 *   Copyright (C) 2014 All rights reserved.
 *   
 *   文件名稱：adc.c
 *   創 建 者：Gavin([email protected])
 *   創建日期：2014年12月15日
 *   描    述：
 *
 ================================================================*/

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include <linux/platform_device.h>
#include <plat/adc.h>
#include <plat/regs-adc.h>

MODULE_LICENSE ("GPL");

int adc_major = 250;
int adc_minor = 0;
int number_of_devices = 1;
struct s3c_adc_client *client;

static struct class *cls;

struct cdev cdev;
dev_t devno = 0;

static ssize_t adc_mini2440_read(struct file *file, char __user *buff, size_t count, loff_t *offset) 
{
	unsigned int data;
	unsigned int ch;
	data = 10;
	ch = 0;

	/*read*/
	data = s3c_adc_read(client, ch);
	printk("data0 = %d\n", data);

	if(copy_to_user(buff, (char *)&data, sizeof(data)))
		return -EFAULT;

	return 0;
}

static int adc_mini2440_open(struct inode *inode, struct file *file)
{
	return 0;
}

static int adc_mini2440_release(struct inode *inode, struct file *file)
{
	return 0;
}

static struct file_operations adc_mini2440_fops = {
	.owner	 = 	THIS_MODULE,
	.read	 = 	adc_mini2440_read,
	.open	 = 	adc_mini2440_open,
	.release =	adc_mini2440_release,
};
static int __devinit adc_mini2440_probe( struct platform_device *pdev )
{
	struct device *dev = &pdev->dev;
	int ret;

	printk("mini2440 adc : function = %s\n", __func__);
	devno = MKDEV(adc_major, adc_minor);
	/* 申請設備 */
	ret = register_chrdev_region(devno, number_of_devices, "mini2440_adc");
	if(ret) {
		dev_err(dev, "failed to register device number\n");
		goto err_register_chrdev_region;
	}
	/*初始化設備*/
	cdev_init(&cdev, &adc_mini2440_fops);
	cdev.owner = THIS_MODULE;
	/* 加入到內核 */
	ret = cdev_add(&cdev, devno, number_of_devices);
	if(ret) {
		dev_err(dev, "failed to add device\n");
		goto err_cdev_add;
	}
	/* 申請adc */
	client = s3c_adc_register (pdev, NULL, NULL, 0);
	if(IS_ERR(client)) {
		dev_err(dev, "failed to register adc client\n");
		goto err_s3c_adc_register;
	}
	/* 創class自動創建節點 */
	cls = class_create(THIS_MODULE, "s3c_adc");
	device_create(cls, NULL, MKDEV(adc_major, 0), NULL, "adc");

	return 0;

err_s3c_adc_register:
	cdev_del(&cdev);
err_cdev_add:
	unregister_chrdev_region(devno, number_of_devices);
err_register_chrdev_region:

	return ret; 
}

static int __devexit adc_mini2440_remove(struct platform_device *pdev)
{
	s3c_adc_release(client);
	device_destroy(cls, MKDEV(adc_major, 0));
	class_destroy(cls);
	cdev_del(&cdev);
	unregister_chrdev_region(devno, number_of_devices);

	return 0;
}

static struct platform_driver adc_mini2440_driver = {
	.driver = {
		.name = "mini2440_adc",
		.owner = THIS_MODULE,
	},
	.probe	= adc_mini2440_probe,
	.remove = __devexit_p(adc_mini2440_remove)
};

static int __init adc_mini2440_init (void)
{
	return platform_driver_register( &adc_mini2440_driver );
}

static void __exit adc_mini2440_exit (void) 
{
	platform_driver_unregister(&adc_mini2440_driver );
}

module_init (adc_mini2440_init);
module_exit (adc_mini2440_exit);

3. Makefile：

NAME=adc
obj-m = $(NAME).o
PATH_=/home/nfs_share/rootfs

KERN_DIR := /home/lu/study_mini2440/kernel/linux-2.6.32.2_mini22440/

#用uname -r可顯示出內核版本號
PWD := $(shell pwd)

all:
	make -C $(KERN_DIR)   M=$(PWD)  modules
	sudo cp $(NAME).ko $(PATH_)
	sudo chmod 777 $(PATH_) $(NAME).ko

clean:
	rm -rf *.o  *.ko  *.mod.c  *.order  *.symvers

4. 測試文件：

/*===============================================================
 *   Copyright (C) 2014 All rights reserved.
 *   
 *   文件名稱：test.c
 *   創 建 者：Gavin
 *   創建日期：2014年12月15日
 *   描    述：
 *
 ================================================================*/
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>

int main (void) 
{
	int fd;
	int data;
	
	fd = open ("/dev/adc",O_RDWR);
	if (fd < 0) {
		perror("open");
		return -1;
	}
	
	while(1)
	{
		read (fd, (char *)&data, sizeof(data));
		printf("Voltage = %.2f\n", 3.3/1024*data);
		sleep(1);
	}
	
	close (fd);
	printf ("/dev/adc closed :)\n");
	
	return 0;
}

附：linux通用adc接口：

/* arch/arm/plat-s3c24xx/adc.c
 *
 * Copyright (c) 2008 Simtec Electronics
 *	http://armlinux.simtec.co.uk/
 *	Ben Dooks <[email protected]>, <[email protected]>
 *
 * S3C24XX ADC device core
 *
 * 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; either version 2 of the License.
*/

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/list.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/io.h>

#include <plat/regs-adc.h>
#include <plat/adc.h>

/* This driver is designed to control the usage of the ADC block between
 * the touchscreen and any other drivers that may need to use it, such as
 * the hwmon driver.
 *
 * Priority will be given to the touchscreen driver, but as this itself is
 * rate limited it should not starve other requests which are processed in
 * order that they are received.
 *
 * Each user registers to get a client block which uniquely identifies it
 * and stores information such as the necessary functions to callback when
 * action is required.
 */

struct s3c_adc_client {
	struct platform_device	*pdev;
	struct list_head	 pend;
	wait_queue_head_t	*wait;

	unsigned int		 nr_samples;
	int			 result;
	unsigned char		 is_ts;
	unsigned char		 channel;

	void	(*select_cb)(struct s3c_adc_client *c, unsigned selected);
	void	(*convert_cb)(struct s3c_adc_client *c,
			      unsigned val1, unsigned val2,
			      unsigned *samples_left);
};

struct adc_device {
	struct platform_device	*pdev;
	struct platform_device	*owner;
	struct clk		*clk;
	struct s3c_adc_client	*cur;
	struct s3c_adc_client	*ts_pend;
	void __iomem		*regs;

	unsigned int		 prescale;

	int			 irq;
};

static struct adc_device *adc_dev;

static LIST_HEAD(adc_pending);

#define adc_dbg(_adc, msg...) dev_dbg(&(_adc)->pdev->dev, msg)

static inline void s3c_adc_convert(struct adc_device *adc)
{
	unsigned con = readl(adc->regs + S3C2410_ADCCON);

	con |= S3C2410_ADCCON_ENABLE_START;
	writel(con, adc->regs + S3C2410_ADCCON);
}

static inline void s3c_adc_select(struct adc_device *adc,
				  struct s3c_adc_client *client)
{
	unsigned con = readl(adc->regs + S3C2410_ADCCON);

	client->select_cb(client, 1);

	con &= ~S3C2410_ADCCON_MUXMASK;
	con &= ~S3C2410_ADCCON_STDBM;
	con &= ~S3C2410_ADCCON_STARTMASK;

	if (!client->is_ts)
		con |= S3C2410_ADCCON_SELMUX(client->channel);

	writel(con, adc->regs + S3C2410_ADCCON);
}

static void s3c_adc_dbgshow(struct adc_device *adc)
{
	adc_dbg(adc, "CON=%08x, TSC=%08x, DLY=%08x\n",
		readl(adc->regs + S3C2410_ADCCON),
		readl(adc->regs + S3C2410_ADCTSC),
		readl(adc->regs + S3C2410_ADCDLY));
}

static void s3c_adc_try(struct adc_device *adc)
{
	struct s3c_adc_client *next = adc->ts_pend;

	if (!next && !list_empty(&adc_pending)) {
		next = list_first_entry(&adc_pending,
					struct s3c_adc_client, pend);
		list_del(&next->pend);
	} else
		adc->ts_pend = NULL;

	if (next) {
		adc_dbg(adc, "new client is %p\n", next);
		adc->cur = next;
		s3c_adc_select(adc, next);
		s3c_adc_convert(adc);
		s3c_adc_dbgshow(adc);
	}
}

int s3c_adc_start(struct s3c_adc_client *client,
		  unsigned int channel, unsigned int nr_samples)
{
	struct adc_device *adc = adc_dev;
	unsigned long flags;

	if (!adc) {
		printk(KERN_ERR "%s: failed to find adc\n", __func__);
		return -EINVAL;
	}

	if (client->is_ts && adc->ts_pend)
		return -EAGAIN;

	local_irq_save(flags);

	client->channel = channel;
	client->nr_samples = nr_samples;

	if (client->is_ts)
		adc->ts_pend = client;
	else
		list_add_tail(&client->pend, &adc_pending);

	if (!adc->cur)
		s3c_adc_try(adc);
	local_irq_restore(flags);

	return 0;
}
EXPORT_SYMBOL_GPL(s3c_adc_start);

static void s3c_convert_done(struct s3c_adc_client *client,
			     unsigned v, unsigned u, unsigned *left)
{
	client->result = v;
	wake_up(client->wait);
}

int s3c_adc_read(struct s3c_adc_client *client, unsigned int ch)
{
	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wake);
	int ret;

	client->convert_cb = s3c_convert_done;
	client->wait = &wake;
	client->result = -1;

	ret = s3c_adc_start(client, ch, 1);
	if (ret < 0)
		goto err;

	ret = wait_event_timeout(wake, client->result >= 0, HZ / 2);
	if (client->result < 0) {
		ret = -ETIMEDOUT;
		goto err;
	}

	client->convert_cb = NULL;
	return client->result;

err:
	return ret;
}
EXPORT_SYMBOL_GPL(s3c_adc_read);

static void s3c_adc_default_select(struct s3c_adc_client *client,
				   unsigned select)
{
}

struct s3c_adc_client *s3c_adc_register(struct platform_device *pdev,
					void (*select)(struct s3c_adc_client *client,
						       unsigned int selected),
					void (*conv)(struct s3c_adc_client *client,
						     unsigned d0, unsigned d1,
						     unsigned *samples_left),
					unsigned int is_ts)
{
	struct s3c_adc_client *client;

	WARN_ON(!pdev);

	if (!select)
		select = s3c_adc_default_select;

	if (!pdev)
		return ERR_PTR(-EINVAL);

	client = kzalloc(sizeof(struct s3c_adc_client), GFP_KERNEL);
	if (!client) {
		dev_err(&pdev->dev, "no memory for adc client\n");
		return ERR_PTR(-ENOMEM);
	}

	client->pdev = pdev;
	client->is_ts = is_ts;
	client->select_cb = select;
	client->convert_cb = conv;

	return client;
}
EXPORT_SYMBOL_GPL(s3c_adc_register);

void s3c_adc_release(struct s3c_adc_client *client)
{
	/* We should really check that nothing is in progress. */
	if (adc_dev->cur == client)
		adc_dev->cur = NULL;
	if (adc_dev->ts_pend == client)
		adc_dev->ts_pend = NULL;
	else {
		struct list_head *p, *n;
		struct s3c_adc_client *tmp;

		list_for_each_safe(p, n, &adc_pending) {
			tmp = list_entry(p, struct s3c_adc_client, pend);
			if (tmp == client)
				list_del(&tmp->pend);
		}
	}

	if (adc_dev->cur == NULL)
		s3c_adc_try(adc_dev);
	kfree(client);
}
EXPORT_SYMBOL_GPL(s3c_adc_release);

static irqreturn_t s3c_adc_irq(int irq, void *pw)
{
	struct adc_device *adc = pw;
	struct s3c_adc_client *client = adc->cur;
	unsigned long flags;
	unsigned data0, data1;

	if (!client) {
		dev_warn(&adc->pdev->dev, "%s: no adc pending\n", __func__);
		return IRQ_HANDLED;
	}

	data0 = readl(adc->regs + S3C2410_ADCDAT0);
	data1 = readl(adc->regs + S3C2410_ADCDAT1);
	adc_dbg(adc, "read %d: 0x%04x, 0x%04x\n", client->nr_samples, data0, data1);

	client->nr_samples--;

	if (client->convert_cb)
		(client->convert_cb)(client, data0 & 0x3ff, data1 & 0x3ff,
				     &client->nr_samples);

	if (client->nr_samples > 0) {
		/* fire another conversion for this */

		client->select_cb(client, 1);
		s3c_adc_convert(adc);
	} else {
		local_irq_save(flags);
		(client->select_cb)(client, 0);
		adc->cur = NULL;

		s3c_adc_try(adc);
		local_irq_restore(flags);
	}

	return IRQ_HANDLED;
}

static int s3c_adc_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct adc_device *adc;
	struct resource *regs;
	int ret;

	adc = kzalloc(sizeof(struct adc_device), GFP_KERNEL);
	if (adc == NULL) {
		dev_err(dev, "failed to allocate adc_device\n");
		return -ENOMEM;
	}

	adc->pdev = pdev;
	adc->prescale = S3C2410_ADCCON_PRSCVL(49);

	adc->irq = platform_get_irq(pdev, 1);
	if (adc->irq <= 0) {
		dev_err(dev, "failed to get adc irq\n");
		ret = -ENOENT;
		goto err_alloc;
	}

	ret = request_irq(adc->irq, s3c_adc_irq, 0, dev_name(dev), adc);
	if (ret < 0) {
		dev_err(dev, "failed to attach adc irq\n");
		goto err_alloc;
	}

	adc->clk = clk_get(dev, "adc");
	if (IS_ERR(adc->clk)) {
		dev_err(dev, "failed to get adc clock\n");
		ret = PTR_ERR(adc->clk);
		goto err_irq;
	}

	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!regs) {
		dev_err(dev, "failed to find registers\n");
		ret = -ENXIO;
		goto err_clk;
	}

	adc->regs = ioremap(regs->start, resource_size(regs));
	if (!adc->regs) {
		dev_err(dev, "failed to map registers\n");
		ret = -ENXIO;
		goto err_clk;
	}

	clk_enable(adc->clk);

	writel(adc->prescale | S3C2410_ADCCON_PRSCEN,
	       adc->regs + S3C2410_ADCCON);

	dev_info(dev, "attached adc driver\n");

	platform_set_drvdata(pdev, adc);
	adc_dev = adc;

	return 0;

 err_clk:
	clk_put(adc->clk);

 err_irq:
	free_irq(adc->irq, adc);

 err_alloc:
	kfree(adc);
	return ret;
}

static int s3c_adc_remove(struct platform_device *pdev)
{
	struct adc_device *adc = platform_get_drvdata(pdev);

	iounmap(adc->regs);
	free_irq(adc->irq, adc);
	clk_disable(adc->clk);
	clk_put(adc->clk);
	kfree(adc);

	return 0;
}

#ifdef CONFIG_PM
static int s3c_adc_suspend(struct platform_device *pdev, pm_message_t state)
{
	struct adc_device *adc = platform_get_drvdata(pdev);
	u32 con;

	con = readl(adc->regs + S3C2410_ADCCON);
	con |= S3C2410_ADCCON_STDBM;
	writel(con, adc->regs + S3C2410_ADCCON);

	clk_disable(adc->clk);

	return 0;
}

static int s3c_adc_resume(struct platform_device *pdev)
{
	struct adc_device *adc = platform_get_drvdata(pdev);

	clk_enable(adc->clk);

	writel(adc->prescale | S3C2410_ADCCON_PRSCEN,
	       adc->regs + S3C2410_ADCCON);

	return 0;
}

#else
#define s3c_adc_suspend NULL
#define s3c_adc_resume NULL
#endif

static struct platform_driver s3c_adc_driver = {
	.driver		= {
		.name	= "s3c24xx-adc",
		.owner	= THIS_MODULE,
	},
	.probe		= s3c_adc_probe,
	.remove		= __devexit_p(s3c_adc_remove),
	.suspend	= s3c_adc_suspend,
	.resume		= s3c_adc_resume,
};

static int __init adc_init(void)
{
	int ret;

	ret = platform_driver_register(&s3c_adc_driver);
	if (ret)
		printk(KERN_ERR "%s: failed to add adc driver\n", __func__);

	return ret;
}

arch_initcall(adc_init);