linux-kernel - Re: [PATCH] video/smscufx: fix line counting in fb

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Date:	Sun, 13 May 2012 12:47:55 +0000
From:	Florian Tobias Schandinat <FlorianSchandinat@....de>
To:	Alexander Holler <holler@...oftware.de>
CC:	linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org
Subject: Re: [PATCH] video/smscufx: fix line counting in fb_write

Hi Alexander,

On 04/21/2012 11:26 AM, Alexander Holler wrote:
> Hello,
> 
> as for the patch for udlfb, I forgot to mention that this is a candidate
> for all stable trees 3.2 and above.
> 
> Btw., the address of the maintainer doesn't seem to be valid anymore.

it is better to cc me on patches to the framebuffer subsystem for such
cases. I don't have much free time so it's rare that I come around to
dig in the mailing list.

> 
> Regards,
> 
> Alexander
> 
> Am 21.04.2012 00:11, schrieb Alexander Holler:
>> Line 0 and 1 were both written to line 0 (on the display) and all
>> subsequent
>> lines had an offset of -1. The result was that the last line on the
>> display
>> was never overwritten by writes to /dev/fbN.
>>
>> The origin of this bug seems to have been udlfb.
>>
>> Signed-off-by: Alexander Holler<holler@...oftware.de>
> 
> Cc: stable@...r.kernel.org

Patch looks good to me but can be made simpler.

> 
>> ---
>>   drivers/video/smscufx.c |    2 +-
>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/video/smscufx.c b/drivers/video/smscufx.c
>> index ccbfef5..1e1e2d2 100644
>> --- a/drivers/video/smscufx.c
>> +++ b/drivers/video/smscufx.c
>> @@ -904,7 +904,7 @@ static ssize_t ufx_ops_write(struct fb_info *info,
>> const char __user *buf,
>>       result = fb_sys_write(info, buf, count, ppos);
>>
>>       if (result>  0) {
>> -        int start = max((int)(offset / info->fix.line_length) - 1, 0);
>> +        int start = max((int)(offset / info->fix.line_length), 0);

the cast to int as well as the max is superfluous without the -1 as the
value can no longer be negative.

>>           int lines = min((u32)((result / info->fix.line_length) + 1),
>>                   (u32)info->var.yres);
>>
> 

Best regards,

Florian Tobias Schandinat
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