Comment by comex

The EFI environment does provide some basic drivers for the boot environment, but they all go away once the OS loads, except for a handful of functions such as EFI variable management. (Linux can also reuse a framebuffer originally obtained from EFI for a very limited form of video support - efifb - but that’s not proper video support.) So EFI doesn’t get credit for video drivers or power management.

For power management, you can however give some credit to ACPI, which is not directly related to UEFI (it predates it), but is likewise an open standard, and is generally found on the same devices as UEFI (i.e. PCs and ARM servers). ACPI also provides the initial gateway to PCIe, another open standard; so if you have a discrete video card then you can theoretically access it without chipset-specific drivers (but of course you still need a driver for the card itself).

But for onboard video, and I believe a good chunk of power management as well, the credit goes to drivers written for Linux by the hardware vendors.