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Date: Mon, 14 Feb 2011 18:04:33 +0100 (CET)
From: Julia Lawall <julia@diku.dk>
To: Marek Vasut <marek.vasut@gmail.com>
Cc: ben-linux@fluff.org, kernel-janitors@vger.kernel.org,
        Baruch Siach <baruch@tkos.co.il>, Dave Airlie <airlied@linux.ie>,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/5] drivers/i2c/busses/i2c-nuc900.c: Convert release_resource
 to release_region/release_mem_region
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On Mon, 14 Feb 2011, Marek Vasut wrote:

> On Sunday 13 February 2011 13:12:12 Julia Lawall wrote:
> > Request_region should be used with release_region, not release_resource.
> > 
> > The result of request_mem_region is no longer stored.  Instead the field
> > ioarea is used to store a pointer to the resource structure that contains
> > the start address.  This is the information that is needed later in
> > nuc900_i2c_remove to release the region.  The field ioarea is also printed
> > in some debugging code.
> > 
> > The semantic match that finds this problem is as follows:
> > (http://coccinelle.lip6.fr/)
> > 
> > // <smpl>
> > @@
> > expression x,E;
> > @@
> > (
> > *x = request_region(...)
> > 
> > *x = request_mem_region(...)
> > )
> > ... when != release_region(x)
> >     when != x = E
> > * release_resource(x);
> > // </smpl>
> > 
> > Signed-off-by: Julia Lawall <julia@diku.dk>
> > 
> > ---
> > Not compiled due to incompatible architecture.
> > 
> >  drivers/i2c/busses/i2c-nuc900.c |   13 +++++--------
> >  1 file changed, 5 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-nuc900.c
> > b/drivers/i2c/busses/i2c-nuc900.c index 7243426..97b16b7 100644
> > --- a/drivers/i2c/busses/i2c-nuc900.c
> > +++ b/drivers/i2c/busses/i2c-nuc900.c
> > @@ -568,15 +568,13 @@ static int __devinit nuc900_i2c_probe(struct
> > platform_device *pdev) goto err_clk;
> >  	}
> > 
> > -	i2c->ioarea = request_mem_region(res->start, resource_size(res),
> > -					 pdev->name);
> > -
> > -	if (i2c->ioarea == NULL) {
> > +	if (!request_mem_region(res->start, resource_size(res), pdev->name)) {
> 
> I prefer the original version here -- it's clearer and also, doesn't the new 
> version violate line-over-80 principle ?

The line ends before column 80.

I'm not sure that the result of request_mem_region is the proper argment 
to give to release_region.  In any case, all of the other calls to 
request_mem_region that do use release_region do not use the return value.  
They just test it directly as I have done here.

julia

> >  		dev_err(&pdev->dev, "cannot request IO\n");
> >  		ret = -ENXIO;
> >  		goto err_clk;
> >  	}
> > 
> > +	i2c->ioarea = res;
> >  	i2c->regs = ioremap(res->start, resource_size(res));
> > 
> >  	if (i2c->regs == NULL) {
> > @@ -645,8 +643,7 @@ static int __devinit nuc900_i2c_probe(struct
> > platform_device *pdev) iounmap(i2c->regs);
> > 
> >   err_ioarea:
> > -	release_resource(i2c->ioarea);
> > -	kfree(i2c->ioarea);
> > +	release_mem_region(res->start, resource_size(res));
> > 
> >   err_clk:
> >  	clk_disable(i2c->clk);
> > @@ -665,6 +662,7 @@ static int __devinit nuc900_i2c_probe(struct
> > platform_device *pdev) static int __devexit nuc900_i2c_remove(struct
> > platform_device *pdev) {
> >  	struct nuc900_i2c *i2c = platform_get_drvdata(pdev);
> > +	struct resource *res = i2c->ioarea;
> 
> No need for this ...
> > 
> >  	i2c_del_adapter(&i2c->adap);
> >  	free_irq(i2c->irq, i2c);
> > @@ -674,8 +672,7 @@ static int __devexit nuc900_i2c_remove(struct
> > platform_device *pdev)
> > 
> >  	iounmap(i2c->regs);
> > 
> > -	release_resource(i2c->ioarea);
> > -	kfree(i2c->ioarea);
> 
> ... the i2c pointer is still available here, why introducing struct resource 
> *res. release_mem_region() looks like a sane change to me though.
> 
> > +	release_mem_region(res->start, resource_size(res));
> >  	kfree(i2c);
> > 
> >  	return 0;
> --
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