repaper_spi_transfer
ret = repaper_spi_transfer(spi, 0x70, ®, NULL, 1);
return repaper_spi_transfer(spi, 0x72, buf, NULL, len);
ret = repaper_spi_transfer(spi, 0x70, ®, NULL, 1);
ret = repaper_spi_transfer(spi, 0x73, NULL, &val, 1);
ret = repaper_spi_transfer(spi, 0x71, NULL, &id, 1);