linux-kernel - Re: [PATCH 09/26] ARM: OMAP: dmtimer: Get rid of check for mem resource error

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Message-ID: <20140507222238.GF19102@atomide.com>
Date:	Wed, 7 May 2014 15:22:39 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Joel Fernandes <joelf@...com>
Cc:	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/26] ARM: OMAP: dmtimer: Get rid of check for mem
 resource error

* Joel Fernandes <joelf@...com> [140507 15:15]:
> On 05/07/2014 05:10 PM, Tony Lindgren wrote:
> > * Joel Fernandes <joelf@...com> [140507 14:53]:
> >> On 05/07/2014 10:24 AM, Tony Lindgren wrote:
> >>> * Joel Fernandes <joelf@...com> [140424 14:44]:
> >>>> The subsequent devm_ioremap_resource will catch it and print an error, let it
> >>>> be checked there.
> >>>>
> >>>> Signed-off-by: Joel Fernandes <joelf@...com>
> >>>> ---
> >>>>  arch/arm/plat-omap/dmtimer.c |    4 ----
> >>>>  1 file changed, 4 deletions(-)
> >>>>
> >>>> diff --git a/arch/arm/plat-omap/dmtimer.c b/arch/arm/plat-omap/dmtimer.c
> >>>> index 7e806f9..1fd30fa 100644
> >>>> --- a/arch/arm/plat-omap/dmtimer.c
> >>>> +++ b/arch/arm/plat-omap/dmtimer.c
> >>>> @@ -810,10 +810,6 @@ static int omap_dm_timer_probe(struct platform_device *pdev)
> >>>>  	}
> >>>>  
> >>>>  	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >>>> -	if (unlikely(!mem)) {
> >>>> -		dev_err(dev, "%s: no memory resource.\n", __func__);
> >>>> -		return -ENODEV;
> >>>> -	}
> >>>>  
> >>>>  	timer = devm_kzalloc(dev, sizeof(struct omap_dm_timer), GFP_KERNEL);
> >>>>  	if (!timer) {
> >>>
> >>> We still need to return an error here and not try to continue though.
> >>
> >> We are returning an error if mem is NULL so the redundant check is
> >> unnecessary:
> >>
> >> ...
> >>         timer->io_base = devm_ioremap_resource(dev, mem);
> >>         if (IS_ERR(timer->io_base))
> >>                 return PTR_ERR(timer->io_base);
> > 
> > Why would you want to even continue omap_dm_timer_probe()
> > further and allocate memory if platform_get_resource() fails?
> > 
> 
> But its freed anyway on error. I just felt that extra LOC could be
> removed. Ideally we should do something like
> 
> 
> mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> io_base = devm_ioremap_resource(dev, mem);
> if (IS_ERR(io_base))
> 	return PTR_ERR(io_base);
> 
> timer = devm_kzalloc(dev, sizeof(struct omap_dm_timer), GFP_KERNEL);
> if (!timer) {
>  ...
> }
> timer->io_base = io_base;
> 
> 
> That combines the platform_get_resource and devm_ioremap_resource error
> paths into 1 path and avoids redundant checks.. I can do it this way, or
> if you want drop the patch entirely, I'm OK with it both ways..

Just drop the dev_err if anything. Removing error checking from
function calls is always going to cause people to wonder what's
going on.

Tony
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