Fair warning: I have *no* idea what all this is for xD.
The modern variant of this appears to be something like
that, although that's not actually aimed at boards w/ an EPDC, which use an older kernel. Also possibly not aimed at the right boards *at all* (that certainly targets at *least* an i.MX6 w/ a Vivante GPU, which I don't think is the case on Kindle & Kobo, we only have the PXP).
I think *someone* managed to dig up the proper tree from NXP a few months ago (possibly on the Kobo forum), FWIW.
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Back on planet Earth, IIRC, on Kindle, the actual job of requesting eInk refreshes is deferred to awesome via the ligl lua bindings.
That said, I never really looked all that much into it, short of enabling debug logging to mimic its behavior in KOReader.