Quote Originally Posted by Tweenk View Post
The problem here is the closed-source driver, not the change in kernel API. Do not upgrade your kernel if your closed-source driver supplier does not support it. If you don't want the driver supplier to prevent you from kernel upgrades, convince them to release an open-source driver.
And this is the reason no one develops for Linux: Developers will not constantly upgrade their SW because people like you feel the need to constantly re-write the Kernel API's. Then people are stuck choosing between either an old, underperforming Kernel, or unsupported HW. Then, they give up and go back to Windows.

What if some API function turns out later to be poorly designed / unsafe / not general enough? By never removing any functions you prevent the removal of cruft as well as a good deal of improvement.
Mark it as unsafe. Kernel API calls should RARELY be removed, due to compatability reasons. The only time you can make an argument for doing so is in the case where you re-write the entire API from scratch [which I again note should be done very rarely, with VERY close support from the hardware devs].