Hi Zhenhua,
> > Make sure to ofono_call_volume_set_data(cv, NULL) here.
>
> I don't see ofono_call_volume_set_data(cv, NULL) or
> ofono_voicecall_set_data(vc, NULL) from atmodem either. Anyway, I add the
> code in hfp_call_volume_remove.
>

Then that needs to be fixed.  Care to send a patch?

In general you should set_data to NULL before freeing it.

Regards,
-Denis