Re: [PATCH] fb_ddc: Fix DDC lines quirk

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Sun, 2007-11-18 at 14:21 +0100, Jean Delvare wrote:
> The code in fb_ddc_read() is said to be based on the implementation
> of the radeon driver:
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=fc5891c8a3ba284f13994d7bc1f1bfa8283982de
> 
> However, comparing the old radeon driver code with the new fb_ddc code
> reveals some differences. Most notably, the I2C bus lines are held at
> the end of the function, while the original code was releasing them
> (as the comment above correctly says.)

 .../...

> Signed-off-by: Jean Delvare <khali@linux-fr.org>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> ---
>  drivers/video/fb_ddc.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> --- linux-2.6.24-rc3.orig/drivers/video/fb_ddc.c	2007-11-17 20:23:03.000000000 +0100
> +++ linux-2.6.24-rc3/drivers/video/fb_ddc.c	2007-11-18 12:49:14.000000000 +0100
> @@ -56,13 +56,12 @@ unsigned char *fb_ddc_read(struct i2c_ad
>  	int i, j;
>  
>  	algo_data->setscl(algo_data->data, 1);
> -	algo_data->setscl(algo_data->data, 0);
>  
>  	for (i = 0; i < 3; i++) {
>  		/* For some old monitors we need the
>  		 * following process to initialize/stop DDC
>  		 */
> -		algo_data->setsda(algo_data->data, 0);
> +		algo_data->setsda(algo_data->data, 1);
>  		msleep(13);
>  
>  		algo_data->setscl(algo_data->data, 1);
> @@ -97,14 +96,15 @@ unsigned char *fb_ddc_read(struct i2c_ad
>  		algo_data->setsda(algo_data->data, 1);
>  		msleep(15);
>  		algo_data->setscl(algo_data->data, 0);
> +		algo_data->setsda(algo_data->data, 0);
>  		if (edid)
>  			break;
>  	}
>  	/* Release the DDC lines when done or the Apple Cinema HD display
>  	 * will switch off
>  	 */
> -	algo_data->setsda(algo_data->data, 0);
> -	algo_data->setscl(algo_data->data, 0);
> +	algo_data->setsda(algo_data->data, 1);
> +	algo_data->setscl(algo_data->data, 1);
>  
>  	return edid;
>  }
> 
> 


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