1, the development of each driver, the first step to understand the driving framework, drive the difficulty is also understanding the driving framework. For example, the SPI driver is composed of a controller driver and a device driver. In general, we only care about device drivers. The controller driver is supplied by the factory. If you don't understand the SPI's drive frame, you don't know where to start.
2, the driver is generally provided by the original, the development drive, generally can find the corresponding OEM template drive. Understand the original, and then on this basis to modify on it. The drivers to develop themselves starting from 0 are very few. Complex drivers may also have to learn a lot of protocol specifications.
3, there are ready-made drivers can be consulted, we should be concerned about the corresponding equipment how to operate, timing requirements. For example, the installation of the sensor in Sony's sensor, using the SPI. The start setting was unsuccessful and was later found to be unfamiliar with the return of the sensor data. When the SPI is written, sensor gives you the value. If the SPI reads and then goes to SPI Read will read to 0.