How to get value of 'Param' of the WHERE clause in the FDW?

Please help.... I'm doing a following query to a foreign wrapper:
FUNCTION fwcall(text) .... SELECT * FROM fwtable WHERE col=$1.... ;
...
SELECT * from fdwcall('abc123');

I'm looking for a way to get that parameter 'abc123' value in the FDW
wrapper code...

It seems like during fdwPlan(..., RelOptInfo *baserel) stage I'm getting
baserel->baserestrictinfo, in which I see a Node *x of IsA(x, Param).
But it looks like the value 'abc123' is not yet available in the planning
stage, right? And I don't see how can I get baserestrictinfo in the
execution stage or if the 'abc123' value would be there...

Can somebody kick me to the right direction? Please?

Thanks,
Dmitry