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

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Date:   Tue, 25 Oct 2016 13:46:17 +0100
From:   Andrey Utkin <andrey_utkin@...tmail.com>
To:     Mauro Carvalho Chehab <mchehab@...pensource.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()

On Mon, Oct 24, 2016 at 10:11:15PM -0200, Mauro Carvalho Chehab wrote:
> 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);

Now i see that also this should suit style better than original variant:

	dev->isoc_ctl.urb = kcalloc(num_bufs, sizeof(*dev->isoc_ctl.urb),
				    GFP_KERNEL);

That's what vim with github.com/vivien/vim-linux-coding-style plugin
proposes.

> That's worse :)

I was about to send long emotional noobish bikeshedding rant arguing
with this point, but restrained from that keeping in mind that I want to
proceed contributing to the codebase successfully :) I'll keep my coding
style preferences for myself for a while.