Red Hat also customizes the kernel they've standardized on to disable hardware functionality which they do not want to support under SLA; they have two general ways of doing it, disable compilation of the entire module (where possible) or add the specific PCI ID to a filter-out on that module's supported hardware. The methods tend to route through a custom routine in their kernel patches which notify the user the hardware has been seen but will not function/be supported by their kernel.
This goes the other way around a well, they often cherry-pick new code and pull it back into their curated kernels to support the latest hardware offerings of their partners (Dell, HP, Broadcom, etc.) without pulling in possible unstable newer kernel code around it; they have contractors from those hardware companies assisting in the work to backport hardware module features.
This goes the other way around a well, they often cherry-pick new code and pull it back into their curated kernels to support the latest hardware offerings of their partners (Dell, HP, Broadcom, etc.) without pulling in possible unstable newer kernel code around it; they have contractors from those hardware companies assisting in the work to backport hardware module features.