@gaetan mentioned his driver can work without moding the cam (at least that's my understanding), so I ported his changes to the current driver and recompiled but despite I can load the new module with appropriate settings (flashled=1) I still get an error when clicking on the "SPC900 LED" button in the "Long Exposure" tab of the indi_v4l2_ccd panel:
2020-08-05T14:24:30: Can not set Lx Mode to SPC900 LED
2020-08-05T14:24:30: ERROR: device does not support PWC ioctl
Anyone know how to shoot long exposure frames with the SPC900? Is there any solution which doesn't involve soldering and buying more electronic parts?