The Linux kernel provides a general-purpose SPI driver named spidev. The spidev driver is a simple interface that abstracts many of the housekeeping details involved in SPI communications. The spidev driver is exposed via the /dev filesystem as the /dev/spidevX.Y file. Multiple versions of these spidev files can be present depending upon the number of SPI buses configured in the Device Tree. The X value in the spidev filename refers to the SPI controller number (1 for SPI0 and 2 for SPI1), and the Y value refers to the SPI bus of that controller (0 for the first bus and 1 for the second bus). For the examples in this book, you will only be using the first SPI bus of the SPI0 controller, so /dev/spidev1.0 is the only file with which PacktHAL will interact.