MCP4728_GAIN_MASK
outbuf[offset] |= FIELD_PREP(MCP4728_GAIN_MASK, ch->g_mode);
outbuf[1] |= FIELD_PREP(MCP4728_GAIN_MASK, ch->g_mode);
ch->g_mode = FIELD_GET(MCP4728_GAIN_MASK, r2);