28 IIC(六)i2c-dev.c

1. 简介

i2c-dev可以看做一个通用的i2c设备驱动,不过对它而言它是虚拟的。相当于i2c-dev文件实现了一个通用的i2c_driver功能。当然具体的细节就需要放到应用态去实现了。

需要注意的是i2c-dev.c文件中实现的read、write一般而言只能实现单条信息发送。对于两条及其以上信息的发送需要使用ioctl

2 IIC dev 分析

2.1 i2c_dev_init

初始化之前的相关操作

static int __init i2c_dev_init(void)
{
	int res;

	printk(KERN_INFO "i2c /dev entries driver\n");

	/* 注册的主设备号为89 */
	res = register_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS, "i2c");
	if (res)
		goto out;

	i2c_dev_class = class_create(THIS_MODULE, "i2c-dev");
	if (IS_ERR(i2c_dev_class)) {
		res = PTR_ERR(i2c_dev_class);
		goto out_unreg_chrdev;
	}
	i2c_dev_class->dev_groups = i2c_groups;

	/* Keep track of adapters which will be added or removed later */
	/* 通知链 */
	res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier);
	if (res)
		goto out_unreg_class;

	/* Bind to already existing adapters right away */
	/* 遍历每个存在的i2c adapter 调用i2cdev_attach_adapter去注册i2c adapter驱动 */
	i2c_for_each_dev(NULL, i2cdev_attach_adapter);

	return 0;

out_unreg_class:
	class_destroy(i2c_dev_class);
out_unreg_chrdev:
	unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
out:
	printk(KERN_ERR "%s: Driver Initialisation failed\n", __FILE__);
	return res;
}

module_init(i2c_dev_init);

2.2 i2cdev_attach_adapter

i2c adapter注册函数

static int i2cdev_attach_adapter(struct device *dev, void *dummy)
{
	struct i2c_adapter *adap;
	struct i2c_dev *i2c_dev;
	int res;

	if (dev->type != &i2c_adapter_type)
		return 0;
	adap = to_i2c_adapter(dev);

	/* 为adapter分配一个free i2c dev,并将其放入i2c_dev_list */
	i2c_dev = get_free_i2c_dev(adap);
	if (IS_ERR(i2c_dev))
		return PTR_ERR(i2c_dev);

	/* select free i2c dev register chardev and init */
	cdev_init(&i2c_dev->cdev, &i2cdev_fops);
	i2c_dev->cdev.owner = THIS_MODULE;
	res = cdev_add(&i2c_dev->cdev, MKDEV(I2C_MAJOR, adap->nr), 1);
	if (res)
		goto error_cdev;

	/* register this i2c device with the driver core */
	i2c_dev->dev = device_create(i2c_dev_class, &adap->dev,
				     MKDEV(I2C_MAJOR, adap->nr), NULL,
				     "i2c-%d", adap->nr);
	if (IS_ERR(i2c_dev->dev)) {
		res = PTR_ERR(i2c_dev->dev);
		goto error;
	}

	pr_debug("i2c-dev: adapter [%s] registered as minor %d\n",
		 adap->name, adap->nr);
	return 0;
error:
	cdev_del(&i2c_dev->cdev);
error_cdev:
	put_i2c_dev(i2c_dev);
	return res;
}

2.3 i2cdev_fops

i2c dev的核心操作函数

static const struct file_operations i2cdev_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.read		= i2cdev_read,
	.write		= i2cdev_write,
	.unlocked_ioctl	= i2cdev_ioctl,
	.open		= i2cdev_open,
	.release	= i2cdev_release,
};

2.4 i2cdev_open


static int i2cdev_open(struct inode *inode, struct file *file)
{
	unsigned int minor = iminor(inode);
	struct i2c_client *client;
	struct i2c_adapter *adap;

	/* 根据此设备号获取adapter
	 * 因为注册的时候使用89为主设备号,nr即设备的此设备号
	 */
	adap = i2c_get_adapter(minor);
	if (!adap)
		return -ENODEV;

	/* This creates an anonymous i2c_client, which may later be
	 * pointed to some address using I2C_SLAVE or I2C_SLAVE_FORCE.
	 *
	 * This client is ** NEVER REGISTERED ** with the driver model
	 * or I2C core code!!  It just holds private copies of addressing
	 * information and maybe a PEC flag.
	 */
	/* 申请一个空i2c client
	 */
	client = kzalloc(sizeof(*client), GFP_KERNEL);
	if (!client) {
		i2c_put_adapter(adap);
		return -ENOMEM;
	}
	snprintf(client->name, I2C_NAME_SIZE, "i2c-dev %d", adap->nr);

	/* 指定client的adapter,并将client储存到private中
	 */
	client->adapter = adap;
	file->private_data = client;

	return 0;
}

2.5 i2cdev_ioctl


static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct i2c_client *client = file->private_data;
	unsigned long funcs;

	dev_dbg(&client->adapter->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n",
		cmd, arg);

	switch (cmd) {
	/* set client addr */
	case I2C_SLAVE:
	case I2C_SLAVE_FORCE:
		if ((arg > 0x3ff) ||
		    (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
			return -EINVAL;
		if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
			return -EBUSY;
		/* REVISIT: address could become busy later */
		client->addr = arg;
		return 0;
	case I2C_TENBIT:
		if (arg)
			client->flags |= I2C_M_TEN;
		else
			client->flags &= ~I2C_M_TEN;
		return 0;
	case I2C_PEC:
		/*
		 * Setting the PEC flag here won't affect kernel drivers,
		 * which will be using the i2c_client node registered with
		 * the driver model core.  Likewise, when that client has
		 * the PEC flag already set, the i2c-dev driver won't see
		 * (or use) this setting.
		 */
		if (arg)
			client->flags |= I2C_CLIENT_PEC;
		else
			client->flags &= ~I2C_CLIENT_PEC;
		return 0;
	case I2C_FUNCS:
		funcs = i2c_get_functionality(client->adapter);
		return put_user(funcs, (unsigned long __user *)arg);
	/* i2c read and write */
	case I2C_RDWR:
		return i2cdev_ioctl_rdwr(client, arg);

	/* smbus read and write */
	case I2C_SMBUS:
		return i2cdev_ioctl_smbus(client, arg);

	/* 没有收到ack时retry次数 */
	case I2C_RETRIES:
		client->adapter->retries = arg;
		break;

	/* 超时 */
	case I2C_TIMEOUT:
		/* For historical reasons, user-space sets the timeout
		 * value in units of 10 ms.
		 */
		client->adapter->timeout = msecs_to_jiffies(arg * 10);
		break;
	default:
		/* NOTE:  returning a fault code here could cause trouble
		 * in buggy userspace code.  Some old kernel bugs returned
		 * zero in this case, and userspace code might accidentally
		 * have depended on that bug.
		 */
		return -ENOTTY;
	}
	return 0;
}

2.6 i2cdev_ioctl_rdwr

i2c read and write

static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
		unsigned long arg)
{
	struct i2c_rdwr_ioctl_data rdwr_arg;
	struct i2c_msg *rdwr_pa;
	u8 __user **data_ptrs;
	int i, res;

	/* 从用户空间拷贝msg信息 */
	if (copy_from_user(&rdwr_arg,
			   (struct i2c_rdwr_ioctl_data __user *)arg,
			   sizeof(rdwr_arg)))
		return -EFAULT;

	/* Put an arbitrary limit on the number of messages that can
	 * be sent at once */
	if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
		return -EINVAL;

	/* 从用户空间拷贝所有的msg */
	rdwr_pa = memdup_user(rdwr_arg.msgs,
			      rdwr_arg.nmsgs * sizeof(struct i2c_msg));
	if (IS_ERR(rdwr_pa))
		return PTR_ERR(rdwr_pa);

	data_ptrs = kmalloc(rdwr_arg.nmsgs * sizeof(u8 __user *), GFP_KERNEL);
	if (data_ptrs == NULL) {
		kfree(rdwr_pa);
		return -ENOMEM;
	}

	res = 0;
	for (i = 0; i < rdwr_arg.nmsgs; i++) {
		/* Limit the size of the message to a sane amount */
		if (rdwr_pa[i].len > 8192) {
			res = -EINVAL;
			break;
		}

		data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
		rdwr_pa[i].buf = memdup_user(data_ptrs[i], rdwr_pa[i].len);
		if (IS_ERR(rdwr_pa[i].buf)) {
			res = PTR_ERR(rdwr_pa[i].buf);
			break;
		}

		/*
		 * If the message length is received from the slave (similar
		 * to SMBus block read), we must ensure that the buffer will
		 * be large enough to cope with a message length of
		 * I2C_SMBUS_BLOCK_MAX as this is the maximum underlying bus
		 * drivers allow. The first byte in the buffer must be
		 * pre-filled with the number of extra bytes, which must be
		 * at least one to hold the message length, but can be
		 * greater (for example to account for a checksum byte at
		 * the end of the message.)
		 */
		if (rdwr_pa[i].flags & I2C_M_RECV_LEN) {
			if (!(rdwr_pa[i].flags & I2C_M_RD) ||
			    rdwr_pa[i].buf[0] < 1 ||
			    rdwr_pa[i].len < rdwr_pa[i].buf[0] +
					     I2C_SMBUS_BLOCK_MAX) {
				res = -EINVAL;
				break;
			}

			rdwr_pa[i].len = rdwr_pa[i].buf[0];
		}
	}
	if (res < 0) {
		int j;
		for (j = 0; j < i; ++j)
			kfree(rdwr_pa[j].buf);
		kfree(data_ptrs);
		kfree(rdwr_pa);
		return res;
	}

	/* 使用i2c_transfer传输所以msg */
	res = i2c_transfer(client->adapter, rdwr_pa, rdwr_arg.nmsgs);
	while (i-- > 0) {
		if (res >= 0 && (rdwr_pa[i].flags & I2C_M_RD)) {
			/* 如果需要读取,则将读取数据拷贝给用户空间 */
			if (copy_to_user(data_ptrs[i], rdwr_pa[i].buf,
					 rdwr_pa[i].len))
				res = -EFAULT;
		}
		kfree(rdwr_pa[i].buf);
	}
	kfree(data_ptrs);
	kfree(rdwr_pa);
	return res;
}

2.7 i2cdev_ioctl_smbus

static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
		unsigned long arg)
{
	struct i2c_smbus_ioctl_data data_arg;
	union i2c_smbus_data temp = {};
	int datasize, res;

	if (copy_from_user(&data_arg,
			   (struct i2c_smbus_ioctl_data __user *) arg,
			   sizeof(struct i2c_smbus_ioctl_data)))
		return -EFAULT;
	if ((data_arg.size != I2C_SMBUS_BYTE) &&
	    (data_arg.size != I2C_SMBUS_QUICK) &&
	    (data_arg.size != I2C_SMBUS_BYTE_DATA) &&
	    (data_arg.size != I2C_SMBUS_WORD_DATA) &&
	    (data_arg.size != I2C_SMBUS_PROC_CALL) &&
	    (data_arg.size != I2C_SMBUS_BLOCK_DATA) &&
	    (data_arg.size != I2C_SMBUS_I2C_BLOCK_BROKEN) &&
	    (data_arg.size != I2C_SMBUS_I2C_BLOCK_DATA) &&
	    (data_arg.size != I2C_SMBUS_BLOCK_PROC_CALL)) {
		dev_dbg(&client->adapter->dev,
			"size out of range (%x) in ioctl I2C_SMBUS.\n",
			data_arg.size);
		return -EINVAL;
	}
	/* Note that I2C_SMBUS_READ and I2C_SMBUS_WRITE are 0 and 1,
	   so the check is valid if size==I2C_SMBUS_QUICK too. */
	if ((data_arg.read_write != I2C_SMBUS_READ) &&
	    (data_arg.read_write != I2C_SMBUS_WRITE)) {
		dev_dbg(&client->adapter->dev,
			"read_write out of range (%x) in ioctl I2C_SMBUS.\n",
			data_arg.read_write);
		return -EINVAL;
	}

	/* Note that command values are always valid! */

	if ((data_arg.size == I2C_SMBUS_QUICK) ||
	    ((data_arg.size == I2C_SMBUS_BYTE) &&
	    (data_arg.read_write == I2C_SMBUS_WRITE)))
		/* These are special: we do not use data */
		return i2c_smbus_xfer(client->adapter, client->addr,
				      client->flags, data_arg.read_write,
				      data_arg.command, data_arg.size, NULL);

	if (data_arg.data == NULL) {
		dev_dbg(&client->adapter->dev,
			"data is NULL pointer in ioctl I2C_SMBUS.\n");
		return -EINVAL;
	}

	if ((data_arg.size == I2C_SMBUS_BYTE_DATA) ||
	    (data_arg.size == I2C_SMBUS_BYTE))
		datasize = sizeof(data_arg.data->byte);
	else if ((data_arg.size == I2C_SMBUS_WORD_DATA) ||
		 (data_arg.size == I2C_SMBUS_PROC_CALL))
		datasize = sizeof(data_arg.data->word);
	else /* size == smbus block, i2c block, or block proc. call */
		datasize = sizeof(data_arg.data->block);

	if ((data_arg.size == I2C_SMBUS_PROC_CALL) ||
	    (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) ||
	    (data_arg.size == I2C_SMBUS_I2C_BLOCK_DATA) ||
	    (data_arg.read_write == I2C_SMBUS_WRITE)) {
		if (copy_from_user(&temp, data_arg.data, datasize))
			return -EFAULT;
	}
	if (data_arg.size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
		/* Convert old I2C block commands to the new
		   convention. This preserves binary compatibility. */
		data_arg.size = I2C_SMBUS_I2C_BLOCK_DATA;
		if (data_arg.read_write == I2C_SMBUS_READ)
			temp.block[0] = I2C_SMBUS_BLOCK_MAX;
	}
	res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
	      data_arg.read_write, data_arg.command, data_arg.size, &temp);
	if (!res && ((data_arg.size == I2C_SMBUS_PROC_CALL) ||
		     (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) ||
		     (data_arg.read_write == I2C_SMBUS_READ))) {
		if (copy_to_user(data_arg.data, &temp, datasize))
			return -EFAULT;
	}
	return res;
}
posted @ 2023-06-03 15:26  人民广场的二道贩子  阅读(51)  评论(0编辑  收藏  举报