Linux Write down the drive control gpio when , There are two ways ：
- use request_mem_region Functions and ioremap Wait to get the address of the control register , And then use iowrite32 The function controls the gpio
- use gpio_request and gpio_set_value Function to control gpio Pin
- The second is provided by the kernel gpio Subsystem , It's usually used . The first is to realize something similar to the second .
Linux3.0 How to operate the kernel
Because the previous transplant was Linux4.0 kernel , I do not know!
gpio_num Cannot use kernel provided GPIO The operation did not
EXYNOS4_GPL1(0) The macro , So I realize a pin operation enable LVDS：