i2c_check_functionality函数的实现

来源：互联网发布：淘大象软件下载编辑：程序博客网时间：2024/06/16 01:03

下面再来讨论下前面一章中i2c_probe函数中调用的i2c_check_functionality函数的实现。

I2c_probe函数中有这样一段：

/* Stop here if we can't use SMBUS_QUICK */

if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_QUICK)) {

if (address_data->probe[0] == I2C_CLIENT_END

&& address_data->normal_i2c[0] == I2C_CLIENT_END)

return 0;

dev_warn(&adapter->dev, "SMBus Quick command not supported, "

"can't probe for chips\n");

return -1;

}

追踪i2c_check_functionality：

static inline int i2c_check_functionality(struct i2c_adapter *adap, u32 func)

{

return (func & i2c_get_functionality(adap)) == func;

}

static inline u32 i2c_get_functionality(struct i2c_adapter *adap)

{

return adap->algo->functionality(adap);

}

可见还是调用了algothm的functionlity函数。

我们来看看该驱动中这个函数的实现：

static struct i2c_algorithm mxc_i2c_algorithm = {

.master_xfer = mxc_i2c_xfer,

.functionality = mxc_i2c_func

};

static u32 mxc_i2c_func(struct i2c_adapter *adap)

{

return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;

}

可见就是要该适配器支持I2C_FUNC_SMBUS_QUICK的功能。

头文件中I2C_FUNC_I2C和I2C_FUNC_SMBUS_QUICK的定义

I2C_FUNC_I2C                    Plain i2c-level commands (Pure SMBus                                  adapters typically can not do these)

I2C_FUNC_SMBUS_QUICK            Handles the SMBus write_quick command

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