add_prop_float
err = add_prop_float(sensorhdl, (float)env->sd_lo_warn / scale,
err = add_prop_float(sensorhdl, (float)env->sd_lo / scale,
err = add_prop_float(sensorhdl, (float)env->sd_hi_warn / scale,
err = add_prop_float(sensorhdl, (float)env->sd_hi / scale,
static int add_prop_float(picl_nodehdl_t nodeh, float value, char *name);