How can a driver call a driver?

This is an entry-level problem. I used to struggle with Wince and did not know how to solve it.

Later, we saw the camera driver of wince6.0 6410/s5pv210 and found that the call and application between the original driver and the driverProgramThe call driver is the same.

There is no difference at all.

Createfile open another driver
Deviceiocontrol
Gooogleman 22:33:33
The IIC driver is called by the camera driver.
Gooogleman 22:33:36
That's how it works.
Gooogleman 22:33:40
Ok6410 has the source code of the camera driver. You can see what is going on. Haha.