[PATCH] i2c: export bit-banging algo functions

[Daniel Vetter]

On Tue, Feb 28, 2012 at 09:08:17AM +0100, Jean Delvare wrote:
> On Tue, 28 Feb 2012 00:39:39 +0100, Daniel Vetter wrote:
> > 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.
> > 
> > Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > ---
> >  drivers/i2c/algos/i2c-algo-bit.c |    3 ++-
> >  include/linux/i2c-algo-bit.h     |    1 +
> >  2 files changed, 3 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c
> > index 525c734..ad0459c 100644
> > --- a/drivers/i2c/algos/i2c-algo-bit.c
> > +++ b/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
> > diff --git a/include/linux/i2c-algo-bit.h b/include/linux/i2c-algo-bit.h
> > index 4f98148..584ffa0 100644
> > --- a/include/linux/i2c-algo-bit.h
> > +++ b/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 */
> 
> Acked-by: Jean Delvare <khali at linux-fr.org>

I've applied this patch to drm-intel-next, thanks for the feedback.
-Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48