MCP4821_VREF_MV
*val = MCP4821_VREF_MV * state->gain;
mcp4821_calc_scale(MCP4821_VREF_MV, chan->scan_type.realbits, &v, &v2);
mcp4821_calc_scale(MCP4821_VREF_MV * 2,
state->scale_avail[0] = MCP4821_VREF_MV;
state->scale_avail[2] = MCP4821_VREF_MV * 2;