"Way to scroll scanlines (strips) of a bitmap bg via registers"
1.- REG_VCOUNT is a readable register, and tell us in which line, the NDS is painting
2.- If we activate the IRQ_HBLANK interruption and mix with REG_VCOUNT, when we modify the BG2_CX, only will scroll the actual REG_VCOUNT line, so we can make effects like shaking, wavy, scrolling, etc...
3.- It's necessary activate IRQ_VBLANK to make only 192 changes per frame (swiWaitForVBlank();)
NOTES: BG2_CX =_val<<8; means 1pixel scroll, <<4 1/2 pixel scroll, and so on.
Now I'm looking for the way to do with HDMA,