i2c: export bit-banging algo functions

i915 has a hw i2c controller (gmbus) but for a bunch of stupid reasons
we need to be able to fall back to the bit-banging algo on gpio pins.

The current code sets up a 2nd i2c controller for the same i2c bus using
the bit-banging algo. This has a bunch of issues, the major one being
that userspace can directly access this fallback i2c adaptor behind
the drivers back.

But we need to frob a few registers before and after using fallback
gpio bit-banging, so this horribly fails.

The new plan is to only set up one i2c adaptor and transparently fall
back to bit-banging by directly calling the xfer function of the bit-
banging algo in the i2c core.

To make that possible, export the 2 i2c algo functions.

v2: As suggested by Jean Delvare, simply export the i2c_bit_algo
vtable instead of the individual functions.
Acked-by: NJean Delvare <khali@linux-fr.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/i2c/algos/i2c-algo-bit.c

@@ -610,10 +610,11 @@ static u32 bit_func(struct i2c_adapter *adap)
 
 /* -----exported algorithm data: -------------------------------------	*/
 
-static const struct i2c_algorithm i2c_bit_algo = {
+const struct i2c_algorithm i2c_bit_algo = {
 	.master_xfer	= bit_xfer,
 	.functionality	= bit_func,
 };
+EXPORT_SYMBOL(i2c_bit_algo);
 
 /*
  * registering functions to load algorithms at runtime

include/linux/i2c-algo-bit.h

@@ -49,5 +49,6 @@ struct i2c_algo_bit_data {
 
 int i2c_bit_add_bus(struct i2c_adapter *);
 int i2c_bit_add_numbered_bus(struct i2c_adapter *);
+extern const struct i2c_algorithm i2c_bit_algo;
 
 #endif /* _LINUX_I2C_ALGO_BIT_H */