spi驱动程序中的基本设备操作

I need to write an spi driver for omap4 from scratch. I am referring https://lxr.free-electrons.com/source/drivers/spi/spi-omap2-mcspi.c driver code. But, I am unable to understand how basic device operations are handled in this driver code. For example a char driver has the structure I need to write an spi driver for omap4 from sc