Allow setting of direct_samp via init args

[ryansuchocki]

Direct sampling mode can currently only be set via writeSetting(). This adds the option of setting it upon initialisation.

In turn, this allows a user to trigger the mode from a client such as GQRX which has no specific support for writing settings but does allow a free-form device argument string.

[zuckschwerdt]

I see the point. It would be preferable however if GQRX could be changed to enumerate Settings and offer a UI for them or at least offer free-form input for Settings. Any chance for that?

[ryansuchocki]

OK, I'll look into that. My initial observation is that gr-osmosdr (which GQRX uses) doesn't make any calls to writeSetting(), so it would have to be added there as well.

[nmaster2042]

An other way would be to replace gr-osmosdr witch is no very maintened by gr-soapy.
Gr-soapy is now part of GNU Radio.

My Feature request here: gqrx-sdr/gqrx#1267

[paulh002]

Than you should also update the response of get_full_frequency_range it is now returning a minimum of 24 Mhz