[PATCH] i2c-algo-bit: make sure to call pre/post_xfer for bit_test

[Jean Delvare]

Hi Alex,

On Thu, 14 Apr 2011 19:47:06 -0400, Alex Deucher wrote:
> Apparently some distros set i2c-algo-bit.bit_test to 1 by
> default.  In some cases this causes i2c_bit_add_bus
> to fail and prevents the i2c bus from being added.  In the
> radeon case, we fail to add the ddc i2c buses which prevents
> the driver from being able to detect attached monitors.
> The i2c bus works fine even if bit_test fails.  This is likely
> due to gpio switching that is required and handled in the
> pre/post_xfer hooks, so call the pre/post_xfer hooks in the
> bit test as well.
> 
> Fixes:
> https://bugs.freedesktop.org/show_bug.cgi?id=36221
> 
> Cc: Jean Delvare <khali at linux-fr.org>
> Signed-off-by: Alex Deucher <alexdeucher at gmail.com>

Good catch, applied, thanks. I'll also push this to the stable kernel
trees (from .38 down to .34.)

> ---
>  drivers/i2c/algos/i2c-algo-bit.c |   21 ++++++++++++++++++---
>  1 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c
> index 38319a6..e2740e6 100644
> --- a/drivers/i2c/algos/i2c-algo-bit.c
> +++ b/drivers/i2c/algos/i2c-algo-bit.c
> @@ -232,9 +232,16 @@ static int i2c_inb(struct i2c_adapter *i2c_adap)
>   * Sanity check for the adapter hardware - check the reaction of
>   * the bus lines only if it seems to be idle.
>   */
> -static int test_bus(struct i2c_algo_bit_data *adap, char *name)
> +static int test_bus(struct i2c_adapter *i2c_adap, char *name)
>  {
> -	int scl, sda;
> +	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> +	int scl, sda, ret;
> +
> +	if (adap->pre_xfer) {
> +		ret = adap->pre_xfer(i2c_adap);
> +		if (ret < 0)
> +			return -ENODEV;
> +	}
>  
>  	if (adap->getscl == NULL)
>  		pr_info("%s: Testing SDA only, SCL is not readable\n", name);
> @@ -297,11 +304,19 @@ static int test_bus(struct i2c_algo_bit_data *adap, char *name)
>  		       "while pulling SCL high!\n", name);
>  		goto bailout;
>  	}
> +
> +	if (adap->post_xfer)
> +		adap->post_xfer(i2c_adap);
> +
>  	pr_info("%s: Test OK\n", name);
>  	return 0;
>  bailout:
>  	sdahi(adap);
>  	sclhi(adap);
> +
> +	if (adap->post_xfer)
> +		adap->post_xfer(i2c_adap);
> +
>  	return -ENODEV;
>  }
>  
> @@ -607,7 +622,7 @@ static int __i2c_bit_add_bus(struct i2c_adapter *adap,
>  	int ret;
>  
>  	if (bit_test) {
> -		ret = test_bus(bit_adap, adap->name);
> +		ret = test_bus(adap, adap->name);
>  		if (ret < 0)
>  			return -ENODEV;
>  	}


-- 
Jean Delvare