[RESEND PATCH v2] drm/mediatek: Add AFBC support to Mediatek DRM driver

[Justin Green]

> These would be different from the macros that are available in bitfield.h, but
> not *fundamentally* different, so these would look a little redundant...
>
> I think that you refer to that `pitch` variable that's coming from the DRM(/fb)
> API... and bitfield macros are for register access... so I guess that one clean
> way of avoiding the magic shifting (that is purely used to split the 32-bits
> number in two 16-bits 'chunks') would be to perhaps use a union, so that you
> will have something like u.pitch_lsb, u.pitch_msb (with lsb/msb being two u16).

Do you mean something like this?

union pitch_val {
     struct split_pitch_val {
          uint16_t lsb;
          uint16_t msb;
     } split;
     uint32_t val;
};

I think my concern with that approach would be it assumes the compiler
packs structs tightly and it also assumes the endianness of the
machine, whereas a bitshift is maybe more portable. Is this an issue
worth considering since we know this driver will only run on specific
MTK SoCs?