I know this is the wrong Forum but we have this same annoying issue on the Galaxy S and I couldn't find a fix, yet.
My workaround at the moment is:
When I receive a call
- I hold it
- wait a few seconds
- then unhold
Then usually the audio doesn't come from the back speaker anymore.
Would any of you geniuses be able to make the fix you made for the Spica in the Galaxy S Kernel, too? This would be incredibly awesome and I'm sure a lot (!) of people would be very grateful to you (including me of course).
Thanks a lot!