How to read data from a serial (SPI) connection in C?

Question

I am trying to write a program that will be installed on a Linux MCU (Raspberry Pi) that will read serial data coming to it from yet another MCU (something homegrown that I will

Answer 1

On Unix everything is a file

If the spi_bcm2708 driver installed correctly there should be a /dev/whatever file for the device ( or several for accessing the device in different ways).

If one wasn't created automatically you can make an entry with mknod

User space code simply has to open the /dev/whatever file as if it was any other regular file and read/write data from it. That's the whole point of Unix.

edit: that's exactly what the code in the linked question is doing, it's opening the terminal /dev/ttyS0 as a file with open() and reading/writing to it.