Osmocom Sink has three gain,

RF gain

which is the switch for 14dB MGA-81563 amplifier.

IF gain

runs from 0 - 47 dB in osmocom_siggen runs from 0 - 40 dB in osmocom_fft

BB gain

RX: 0 - 62 dB (osmocom_fft)

So I guess the parameters of hackrf_transfer mean:

-l  , set lna gain, means RX(osmocom source) IF gain, 8dB steps , 0-40dB
-i  , set vga(if) gain, means RX(osmocom source) BB gain, 2dB steps, 0-62dB
-x , set TX vga gain, means TX(osmocom sink) IF gain, 1dB steps, 0-47dB
-a , RF gain , controls 14dB MGA-81563 amplifier , and both RX and TX chain have its own MGA-81563, so it works for both RX and TX. 14dB or 0dB

And I think we should update the help info of hackrf_transfer.

And Then

Good catch. I fixed the help in git, and I swiped -i for the IF frequency control since it didn't make any sense for RX VGA (baseband) gain (which is now -g).