linux-kernel - Re: [PATCH 1/3] [media] au0828-video: Use kcalloc() in au0828_init

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Date:   Mon, 24 Oct 2016 22:11:15 -0200
From:   Mauro Carvalho Chehab <mchehab@...pensource.com>
To:     Andrey Utkin <andrey_utkin@...tmail.com>
Cc:     SF Markus Elfring <elfring@...rs.sourceforge.net>,
        linux-media@...r.kernel.org, Hans Verkuil <hans.verkuil@...co.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rafael Lourenço de Lima Chehab 
        <chehabrafael@...il.com>, Shuah Khan <shuah@...nel.org>,
        Wolfram Sang <wsa-dev@...g-engineering.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 1/3] [media] au0828-video: Use kcalloc() in
 au0828_init_isoc()

Em Mon, 24 Oct 2016 23:28:44 +0100
Andrey Utkin <andrey_utkin@...tmail.com> escreveu:

> On Mon, Oct 24, 2016 at 10:59:24PM +0200, SF Markus Elfring wrote:
> > From: Markus Elfring <elfring@...rs.sourceforge.net>
> > Date: Mon, 24 Oct 2016 22:08:47 +0200
> > 
> > * Multiplications for the size determination of memory allocations
> >   indicated that array data structures should be processed.
> >   Thus use the corresponding function "kcalloc".
> > 
> >   This issue was detected by using the Coccinelle software.
> > 
> > * Replace the specification of data types by pointer dereferences
> >   to make the corresponding size determination a bit safer according to
> >   the Linux coding style convention.
> > 
> > Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> > ---
> >  drivers/media/usb/au0828/au0828-video.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/media/usb/au0828/au0828-video.c b/drivers/media/usb/au0828/au0828-video.c
> > index 85dd9a8..85b13c1 100644
> > --- a/drivers/media/usb/au0828/au0828-video.c
> > +++ b/drivers/media/usb/au0828/au0828-video.c
> > @@ -221,15 +221,18 @@ static int au0828_init_isoc(struct au0828_dev *dev, int max_packets,
> >  
> >  	dev->isoc_ctl.isoc_copy = isoc_copy;
> >  	dev->isoc_ctl.num_bufs = num_bufs;
> > -  
> 
> > -	dev->isoc_ctl.urb = kzalloc(sizeof(void *)*num_bufs,  GFP_KERNEL);
> > +	dev->isoc_ctl.urb = kcalloc(num_bufs,
> > +				    sizeof(*dev->isoc_ctl.urb),
> > +				    GFP_KERNEL);  
> 
> What about this (for both hunks)?
> 
> -	dev->isoc_ctl.urb = kzalloc(sizeof(void *)*num_bufs,  GFP_KERNEL);
> +	dev->isoc_ctl.urb =
> +		kcalloc(num_bufs, sizeof(*dev->isoc_ctl.urb), GFP_KERNEL);


That's worse :)

The usual Kernel style is:

		var = foo(bar1,
		          bar2,
		          bar3);

instead of something like:

		var =
		    foo(bar1,
			bar2,
			bar3);

The places where it is different than that is because people ran
./scripts/Lindent to try to follow the Kernel coding style.

On my experiences, at the end, using it caused more harm than
good, IMHO, and cause very weird indentation on lines with
more than 80 columns like the above.

Thanks,
Mauro