drivers/gpu/drm/bridge/fsl-ldb.c:101: possible loss of information.

[David Binderman]

Hello there Laurent,

>Would you be able to send a patch to fix this ?

Sadly, no. My success rate with kernel patches is low enough to make it not worth trying.

Regards

David Binderman


From: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Sent: 09 March 2023 09:26
To: David Binderman <dcb314 at hotmail.com>
Cc: andrzej.hajda at intel.com <andrzej.hajda at intel.com>; neil.armstrong at linaro.org <neil.armstrong at linaro.org>; rfoss at kernel.org <rfoss at kernel.org>; jonas at kwiboo.se <jonas at kwiboo.se>; jernej.skrabec at gmail.com <jernej.skrabec at gmail.com>; airlied at gmail.com <airlied at gmail.com>; daniel at ffwll.ch <daniel at ffwll.ch>; dri-devel at lists.freedesktop.org <dri-devel at lists.freedesktop.org>; linux-kernel at vger.kernel.org <linux-kernel at vger.kernel.org>
Subject: Re: drivers/gpu/drm/bridge/fsl-ldb.c:101: possible loss of information. 
 
Hi David,

On Thu, Mar 09, 2023 at 07:59:34AM +0000, David Binderman wrote:
> Hello there Laurent,
> 
> >We could, but I don't think it will make any difference in practice as
> >the maximum pixel clock frequency supported by the SoC is 80MHz (per
> >LVDS channel). That would result in a 560MHz frequency returned by this
> >function, well below the 31 bits limit.
> 
> Thanks for your explanation. I have a couple of suggestions for possible improvements:
> 
> 1. Your explanatory text in a comment nearby. This helps all readers of the code.
> 
> 2. Might the frequency go up to 300 MHz anytime soon ? The code will stop working then. 
> In this case, I would suggest to put in a run time sanity check to make sure no 31 bit overflow. 

As it's a hardware limit of the SoC, I wouldn't expect so.

This being said, I think adding a UL suffix to the constants would be
better than a comment as it will please static checkers and serve as
documentation to humans. Would you be able to send a patch to fix this ?

> Just a couple of ideas for the code.

Thanks for taking the time to share those.

-- 
Regards,

Laurent Pinchart