Re: Kindles, the full story is that, starting with the Oasis 2, there were remnants left in the kernel of an ioctl that would setup frontlight behavior during flashing nightmode updates, to the effect of dimming the frontlight during flashes, with a configurable ramp down/up.
(Which would be
this on mxcfb, and
this on mtk).
To my knowledge, an actual working/complete implementation of this never actually made it to a production kernel, though (I mean, the frontlight driver has code for it, but I don't see the symbol actually being used anywhere by the epdc). Even though the framework was, weirdly, ported to the new MTK driver, so, who knows, it might actually make it in one day.