Function cmd6_mmc_switch 

pub fn cmd6_mmc_switch(access: u8, index: u8, value: u8) -> Command

CMD6 (MMC): SWITCH — modify a single byte of EXT_CSD.

access selects how the value is applied (0b11 = WRITE_BYTE, 0b10 = SET_BITS, 0b01 = CLEAR_BITS). index is the EXT_CSD byte offset (0..511). After issuing this the host must wait for the busy line to clear (R1b) and then poll CMD13 to confirm the card returned to tran and did not set SWITCH_ERROR.