Driver Model

A common Linux driver problem looks like this: the driver is built into the kernel, the Device Tree node exists, but probe never runs. Or probe runs but cannot obtain resources. Or the module loads successfully, but no device node appears.

If you only stare at the driver C file, this kind of problem is easy to misread.

A Linux driver is not “a hardware library function called by an application.” It first has to enter the kernel device model. The kernel needs to know which devices exist, which drivers exist, and what rules match them. Only after a match succeeds does the driver get a chance to initialize the hardware.