> The manufacturers would then write device drivers that implement / fulfill the functionality of these open/generic APIs. (This is how things are done on PCs.)

> The manufacturers would then write device drivers that implement / fulfill the functionality of these open/generic APIs. (This is how things are done on PCs.) This is not a full picture how things work on PCs. There are also dependencies - i.e. you cannot power down the bus, while the device on the other end is not powered down. Things get more interesting, when you have SoC that implements multiple functions and there are interdependecies, where you would not expect them. The entire problem with Skylake mobile chips is, that nobody knows how to properly change the power states and Intel isn't telling anyone. Even linux distros are on their way to manage the system in image-like way. See project atomic, or this video: https://youtu.be/XNLPkMDf9LI https://youtu.be/XNLPkMDf9LI