> I think it should be possible for the client to get away without having 
> to deal with bit-offsets in pixel values directly on 8bit displays, 
> even if these do less than 8 bit colour.

If all FBs which have less depth number than bpp use bits from
LSB in its bpp, bit-offset isn't needed. But I just wonder whether
there is mono framebuffer which uses MSB in bytes (or bits in 2 or 4 bpp).
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Izumi Tsutsui