From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S933850AbcHYKNg (ORCPT <rfc822;w@1wt.eu>);
        Thu, 25 Aug 2016 06:13:36 -0400
Received: from mx2.suse.de ([195.135.220.15]:33998 "EHLO mx2.suse.de"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S933825AbcHYKNe (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 25 Aug 2016 06:13:34 -0400
Message-ID: <1472119708.2877.24.camel@suse.com>
Subject: Re: [PATCH] usbnet: ax88179_178a: Add support for writing the EEPROM
From: Oliver Neukum <oneukum@suse.com>
To: Alban Bedel <alban.bedel@avionic-design.de>
Cc: Freddy Xin <freddy@asix.com.tw>, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org, netdev@vger.kernel.org
Date: Thu, 25 Aug 2016 12:08:28 +0200
In-Reply-To: <20160825120733.3413d395@avionic-0020>
References: <20160824135231.21782-1-alban.bedel@avionic-design.de>
         <1472049039.11480.10.camel@suse.com> <20160824164058.6ec64a8e@avionic-0020>
         <1472116596.2877.23.camel@suse.com> <20160825120733.3413d395@avionic-0020>
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.12.11 
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 2016-08-25 at 12:07 +0200, Alban Bedel wrote:
> On Thu, 25 Aug 2016 11:16:36 +0200
> Oliver Neukum <oneukum@suse.com> wrote:
> 
> > On Wed, 2016-08-24 at 16:40 +0200, Alban Bedel wrote:
> > > On Wed, 24 Aug 2016 16:30:39 +0200
> > > Oliver Neukum <oneukum@suse.com> wrote:
> > >   
> > > > On Wed, 2016-08-24 at 15:52 +0200, Alban Bedel wrote:  
> > 
> > > > > +       if (block != data)
> > > > > +               kfree(block);    
> > > > 
> > > > And if block == dta, what frees the memory?  
> > > 
> > > In this case this function didn't allocate any memory, so there is
> > > nothing to free.  
> > 
> > Hi,
> > 
> > I see. kfree() has a check for NULL, so you could drop the
> > test, but it doesn't matter much either way.
> 
> I think you misunderstand something here. data is the buffer passed
> by the caller and block is a local variable. There is two cases:
> 
> 1) The data to write is block aligned, then we use the caller buffer
>    as is and set block = data.
> 2) The requested data is not block aligned, then we kalloc block.
> 
> In both case the writing loop then use the block pointer. Afterwards
> we only need to kfree block in case 2, that is when block != data.

Thanks for the clarification. Maybe worth a comment in the code?

	Regards
		Oliver