linux-kernel - 在哪里可以找到 i2c“master_xfer”函数的一般定义？

Question

struct i2c_algorithmmaster_xfer具有用于 i2c 总线实现的函数指针模板。我在哪里可以找到master_xferlinux内核源代码中的默认函数例程。？请有人指导我..

Answer 1

master_xfer 的设置取决于您的平台和总线。在 drivers/i2c/busses/ 下查找该函数指针的设置位置。请注意，它可以设置为 NULL。

在 drivers/i2c/busses/i2c-pxa.c 中设置了一个示例：

static const struct i2c_algorithm i2c_pxa_algorithm = {
        .master_xfer    = i2c_pxa_xfer,
        .functionality  = i2c_pxa_functionality,
};

另请查看 include/linux/i2c.h：

struct i2c_algorithm {
        /* If an adapter algorithm can't do I2C-level access, set master_xfer
           to NULL. If an adapter algorithm can do SMBus access, set
           smbus_xfer. If set to NULL, the SMBus protocol is simulated
           using common I2C messages */
        /* master_xfer should return the number of messages successfully
           processed, or a negative value on error */
        int (*master_xfer)(struct i2c_adapter *adap, struct i2c_msg *msgs,
                           int num);
        int (*smbus_xfer) (struct i2c_adapter *adap, u16 addr,
                           unsigned short flags, char read_write,
                           u8 command, int size, union i2c_smbus_data *data);

        /* To determine what the adapter supports */
        u32 (*functionality) (struct i2c_adapter *);
};

：

 * An i2c_msg is the low level representation of one segment of an I2C
 * transaction.  It is visible to drivers in the @i2c_transfer() procedure,
 * to userspace from i2c-dev, and to I2C adapter drivers through the
 * @i2c_adapter.@master_xfer() method.
 *

Answer 2

/driver/i2c/busses/ 中有 i2c-gpio.c 文件。我们正在用 填充master_xfer函数bit_xfer。它确实有点猛烈的实施。