USRP1 DBSRX read ADC values

I am using USRP1 with DBSRX.

My goal is to implement signal conditioning algorithm. Input is the
frequency, output is the optimal gain settings to utilize the full range
ADCs with saturation below acceptable threshold.

As the RSSI is not available for DBSRX, the idea is to acquire a short
signal and analyze the ADC values. The gain value will be set
according the clipping rate and number of utilized ADC bits.

I need to analyze the ADC values, as the further processing (e.g. CIC)
“corrupts” the signal and the strategy mention above could not be used.

My question is how can I read the ADC values?
Can I use: adc_val = u->read_aux_adc(which_side, which_adc)

In the post
aux_adc inputs stands the AUX_ADC is not wired for DVBRX.

Can anyone give me a hint how to read the ADC values?