Re: [PATCH] i2c: export bit-banging algo functions

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

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-/w4YWyX8dFk@public.gmane.org>
> ---
>  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-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>

-- 
Jean Delvare