Constant imxrt_ral::lcdif::CTRL_CLR::DATA_FORMAT_24_BIT::RW::DROP_UPPER_2_BITS_PER_BYTE

pub const DROP_UPPER_2_BITS_PER_BYTE: u32 = 0x01;

Data input to the block is actually RGB 18 bpp, but there is 1 color per byte, hence the upper 2 bits in each byte do not contain any useful data, and should be dropped.