Re: [PATCH] usbnet: ax88179_178a: Add support for writing the EEPROM

From	Alban Bedel <alban.bedel@avionic-design.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH] usbnet: ax88179_178a: Add support for writing the EEPROM
Date	2016-08-25 12:10 +0200
Message-ID	<s9ZLI-82P-19@gated-at.bofh.it> (permalink)
References	<s9GSK-33R-49@gated-at.bofh.it> <s9Hvs-3yl-15@gated-at.bofh.it> <s9HF7-3BB-19@gated-at.bofh.it> <s9Z90-7za-19@gated-at.bofh.it>
Organization	Avionic Design

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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.

Alban

Thread

[PATCH] usbnet: ax88179_178a: Add support for writing the EEPROM Alban Bedel <alban.bedel@avionic-design.de> - 2016-08-24 16:00 +0200
  Re: [PATCH] usbnet: ax88179_178a: Add support for writing the EEPROM Oliver Neukum <oneukum@suse.com> - 2016-08-24 16:40 +0200
    Re: [PATCH] usbnet: ax88179_178a: Add support for writing the  EEPROM Alban Bedel <alban.bedel@avionic-design.de> - 2016-08-24 16:50 +0200
      Re: [PATCH] usbnet: ax88179_178a: Add support for writing the EEPROM Oliver Neukum <oneukum@suse.com> - 2016-08-25 11:30 +0200
        Re: [PATCH] usbnet: ax88179_178a: Add support for writing the  EEPROM Alban Bedel <alban.bedel@avionic-design.de> - 2016-08-25 12:10 +0200
          Re: [PATCH] usbnet: ax88179_178a: Add support for writing the EEPROM Oliver Neukum <oneukum@suse.com> - 2016-08-25 12:20 +0200

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