This is going to be an involved process, but I think it's a good idea to begin doing error checking in the HAL and reporting errors back up the stack and then aborting appropriately (maybe a HAL abort() function when things really go south? also returning errors when relevant).

Although it's safe to assume on Arduinos that functions will either succeed or fail in an irrecoverable way and therefore it doesn't really matter, on Linux and such this may not be the case. For example, we might not be able to open the GPIO device, or we can't acquire a resource.

I think this would be immensely helpful to consumers of the library, especially on non-Arduino platforms.