Re: [PATCH] fb_ddc: Fix DDC lines quirk

[Jean Delvare <khali@linux-fr.org>]

On Thu, 22 Nov 2007 06:58:49 +1100, Benjamin Herrenschmidt wrote:
> 
> 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>

Thanks. Antonino, this patch fixes two reported regressions. Can you
please send it to Linus before 2.6.24 is released? Thanks.

> 
> > ---
> >  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;
> >  }
> > 
> > 

-- 
Jean Delvare

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