linux i2c driver 2
分析i2c-Dev的注册，此设备是个通用的设备，2cdev只是一个虚拟的从设备，因为它并不对应一个实际的从设备，而是和IIC控制器adapter绑定，只有当用户调用open()打开一个设备文件时，才会创建一个虚拟的client。那么怎么知道该i2cdev对应哪个从设备呢？其实很简单，只需要用户在用户空间多做一个工作，就是通过Iocntl()函数来设定从设备的地址，当然这个从设备必须是挂接在对应的adapter下的。所以i2cdev作为一个虚拟设备，本身并不对应任何设备，但又可以对应任意一个挂接在其依附的adapter下的设备。
struct i2c_dev {
struct list_head list;
struct i2c_adapter *adap;
struct device *dev;
};
static int __init i2c_dev_init(void)
{
int res;
printk(KERN_INFO "i2c /dev entries driver\n");
/*注册i2c设备，为字符设备*/
res = register_chrdev(I2C_MAJOR, "i2c", &i2cdev_fops);
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;
}
/*向总线中加载驱动*/
res = i2c_add_driver(&i2cdev_driver);
if (res)
goto out_unreg_class;
return 0;
out_unreg_class:
class_destroy(i2c_dev_class);
out_unreg_chrdev:
unregister_chrdev(I2C_MAJOR, "i2c");
out:
printk(KERN_ERR "%s: Driver Initialisation failed\n", __FILE__);
return res;
}
在i2c_add_driver(&i2cdev_driver)后会调用<pre name="code" class="cpp" style="color: rgb(51, 51, 51); line-height: 25.984375px;">i2c_register_driver 两个主要操作；
1：driver_register 并绑定device；
2：<span style="font-family: Arial;">bus_for_each_dev(&i2c_bus_type, NULL, driver, __process_new_driver);</span>
int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
{
<span style="white-space:pre"> </span>int res;
<span style="white-space:pre"> </span>/* Can't register until after driver model init */
<span style="white-space:pre"> </span>if (unlikely(WARN_ON(!i2c_bus_type.p)))
<span style="white-space:pre"> </span>/* add the driver to the list of i2c drivers in the driver core */
<span style="white-space:pre"> </span>driver->driver.owner = owner;
<span style="white-space:pre"> </span>driver->driver.bus = &i2c_bus_type;
<span style="white-space:pre"> </span>/* When registration returns, the driver core
<span style="white-space:pre"> </span> * will have called probe() for all matching-but-unbound devices.
<span style="white-space:pre"> </span> */
<span style="white-space:pre"> </span>res = driver_register(&driver->driver);
<span style="white-space:pre"> </span>if (res)
<span style="white-space:pre"> </span>return res;
<span style="white-space:pre"> </span>/* Drivers should switch to dev_pm_ops instead. */
<span style="white-space:pre"> </span>if (driver->suspend)
<span style="white-space:pre"> </span>pr_warn("i2c-core: driver [%s] using legacy suspend method\n",
<span style="white-space:pre"> </span>driver->driver.name);
<span style="white-space:pre"> </span>if (driver->resume)
<span style="white-space:pre"> </span>pr_warn("i2c-core: driver [%s] using legacy resume method\n",
<span style="white-space:pre"> </span>driver->driver.name);
<span style="white-space:pre"> </span>pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);
<span style="white-space:pre"> </span>INIT_LIST_HEAD(&driver->clients);
<span style="white-space:pre"> </span>/* Walk the adapters that are already present */
<span style="white-space:pre"> </span>mutex_lock(&core_lock);
<span style="white-space:pre"> </span>bus_for_each_dev(&i2c_bus_type, NULL, driver, __process_new_driver);
<span style="white-space:pre"> </span>mutex_unlock(&core_lock);
<span style="white-space:pre"> </span>return 0;
}
</pre>在driver_register()并不会绑定；<span style="color:rgb(51,51,51); font-family:Arial; font-size:18.18181800842285px; line-height:25.99431800842285px">因为它无法完成i2cdev_driver和从设备的匹配</span><p></p><p><span style="font-size:18px"><span style="color:rgb(51,51,51); font-family:Arial; line-height:25.99431800842285px"></span></span></p><pre name="code" class="objc">static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
struct i2c_client *client = i2c_verify_client(dev);
struct i2c_driver *driver;
if (!client)
return 0;
/* Attempt an OF style match */
if (of_driver_match_device(dev, drv))
return 1;
driver = to_i2c_driver(drv);
/* match on an id table if there is one */
if (driver->id_table)
return i2c_match_id(driver->id_table, client) != NULL;
return 0;
}
static const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
const struct i2c_client *client)
{
while (id->name[0]) {
if (strcmp(client->name, id->name) == 0)
return id;
id++;
}
return NULL;
}
因为i2c_driver 中没有id table
static struct i2c_driver i2cdev_driver = {
.driver = {
.name = "dev_driver",
},
.attach_adapter= i2cdev_attach_adapter,
.detach_adapter= i2cdev_detach_adapter,
};
调用bus_for_each_dev(&i2c_bus_type, NULL, driver, __process_new_driver);
最后调用static int i2c_do_add_adapter(struct i2c_driver *driver,struct i2c_adapter *adap)
{
/* Detect supported devices on that bus, and instantiate them */
i2c_detect(adap, driver);
/* Let legacy drivers scan this bus for matching devices */
if (driver->attach_adapter) {
/* We ignore the return code; if it fails, too bad */
driver->attach_adapter(adap);
}
return 0;
}
static struct i2c_driver i2cdev_driver = {
.driver = {
.name = "dev_driver",
},
.attach_adapter = i2cdev_attach_adapter,
.detach_adapter = i2cdev_detach_adapter,
};
即i2c_driver的i2cdev_attach_adapter
static int i2cdev_attach_adapter(struct i2c_adapter *adap)
{
struct i2c_dev *i2c_dev;
int res;
i2c_dev = get_free_i2c_dev(adap);
if (IS_ERR(i2c_dev))
return PTR_ERR(i2c_dev);
/* 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;
}
res = device_create_file(i2c_dev->dev, &dev_attr_name);
if (res)
goto error_destroy;
pr_debug("i2c-dev: adapter [%s] registered as minor %d\n",
adap->name, adap->nr);
return 0;
error_destroy:
device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr));
error:
return_i2c_dev(i2c_dev);
return res;
}get_free_i2c_dev实现的功能有
<pre name="code" class="cpp">static struct i2c_dev *get_free_i2c_dev(struct i2c_adapter *adap)
{
struct i2c_dev *i2c_dev;
if (adap->nr >= I2C_MINORS) {
printk(KERN_ERR "i2c-dev: Out of device minors (%d)\n",
adap->nr);
return ERR_PTR(-ENODEV);
}
i2c_dev = kzalloc(sizeof(*i2c_dev), GFP_KERNEL);
if (!i2c_dev)
return ERR_PTR(-ENOMEM);
i2c_dev->adap = adap;
spin_lock(&i2c_dev_list_lock);
list_add_tail(&i2c_dev->list, &i2c_dev_list);
spin_unlock(&i2c_dev_list_lock);
return i2c_dev;
}
根据adapt得到i2cdev；
在调用device_create()函数时
i2c_dev->dev = device_create(i2c_dev_class, &adap->dev, MKDEV(I2C_MAJOR, adap->nr),
NULL,"i2c-%d",adap->nr);
i2c_dev_class是在i2c_dev_init(void)中i2c_dev_class = class_create(THIS_MODULE, "i2c-dev");创建的
到此i2c注册完成；
open函数的映射；
static int i2cdev_open(struct inode *inode, struct file *file)
{
unsigned int minor = iminor(inode);
struct i2c_client *client;
struct i2c_adapter *adap;
struct i2c_dev *i2c_dev;
i2c_dev = i2c_dev_get_by_minor(minor);
if (!i2c_dev)
return -ENODEV;
adap = i2c_get_adapter(i2c_dev->adap->nr);
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.
*/
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);
client->driver = &i2cdev_driver;
client->adapter = adap;
file->private_data = client;
return 0;
}
read write 映射
static ssize_t i2cdev_write(struct file *file, const char __user *buf,
size_t count, loff_t *offset)
{
int ret;
char *tmp;
struct i2c_client *client = file->private_data;
if (count > 8192)
count = 8192;
tmp = memdup_user(buf, count);
if (IS_ERR(tmp))
return PTR_ERR(tmp);
pr_debug("i2c-dev: i2c-%d writing %zu bytes.\n",
iminor(file->f_path.dentry->d_inode), count);
ret = i2c_master_send(client, tmp, count);
kfree(tmp);
return ret;
}
int i2c_master_send(const struct i2c_client *client, const char *buf, int count)
{
int ret;
struct i2c_adapter *adap = client->adapter;
struct i2c_msg msg;
msg.addr = client->addr;
msg.flags = client->flags & I2C_M_TEN;
msg.len = count;
msg.buf = (char *)buf;
ret = i2c_transfer(adap, &msg, 1);
/* If everything went ok (i.e. 1 msg transmitted), return #bytes
transmitted, else error code. */
return (ret == 1) ? count : ret;
}
int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
unsigned long orig_jiffies;
int ret, try;
/* REVISIT the fault reporting model here is weak:
*
* - When we get an error after receiving N bytes from a slave,
* there is no way to report "N".
*
* - When we get a NAK after transmitting N bytes to a slave,
* there is no way to report "N" ... or to let the master
* continue executing the rest of this combined message, if
* that's the appropriate response.
*
* - When for example "num" is two and we successfully complete
* the first message but get an error part way through the
* second, it's unclear whether that should be reported as
* one (discarding status on the second message) or errno
* (discarding status on the first one).
*/
if (adap->algo->master_xfer) {
#ifdef DEBUG
for (ret = 0; ret < num; ret++) {
dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, "
"len=%d%s\n", ret, (msgs[ret].flags & I2C_M_RD)
? 'R' : 'W', msgs[ret].addr, msgs[ret].len,
(msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
}
#endif
if (in_atomic() || irqs_disabled()) {
ret = i2c_trylock_adapter(adap);
if (!ret)
/* I2C activity is ongoing. */
return -EAGAIN;
} else {
i2c_lock_adapter(adap);
}
/* Retry automatically on arbitration loss */
orig_jiffies = jiffies;
for (ret = 0, try = 0; try <= adap->retries; try++) {
<span style="color:#ff0000;">ret = adap->algo->master_xfer(adap, msgs, num);</span>
if (ret != -EAGAIN)
break;
if (time_after(jiffies, orig_jiffies + adap->timeout))
break;
}
i2c_unlock_adapter(adap);
return ret;
} else {
dev_dbg(&adap->dev, "I2C level transfers not supported\n");
return -EOPNOTSUPP;
}
}