linux-kernel - Re: [PATCH v2] regulator: wm831x-dcdc: Use pointer after NULL check

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Date:	Thu, 2 Jul 2015 12:12:13 +0100
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	Maninder Singh <maninder1.s@...sung.com>
Cc:	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"patches@...nsource.wolfsonmicro.com" 
	<patches@...nsource.wolfsonmicro.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	PANKAJ MISHRA <pankaj.m@...sung.com>
Subject: Re: [PATCH v2] regulator: wm831x-dcdc: Use pointer after NULL check

On Thu, Jul 02, 2015 at 11:02:54AM +0000, Maninder Singh wrote:
> Hello charles,
> >> pdata is used before NULL check, so it looks misleading.
> >> If pdata validation is required then we have to
> >> first check for pdata validation, then calculate id,
> >> and then second check for pdata->dcdc[id].
> >> 
> >> and it is better to use !pointer than (pointer == NULL)
> >> 
> >> Signed-off-by: Maninder Singh <maninder1.s@...sung.com>
> >> ---
> 
> >The patch basically looks fine, but it feels a bit like needless
> >churn. The current code is perfectly correct and feels clear
> >enough to me.
> 
> Reason for patch is we are checking a pointer which is already dereferenced 
> before NULL check, which looks misleading.
> If we know code is working correctly, Then we may simply drop NULL check,
> rather than these changes. 

You can't drop the NULL check because then we might dereference a
NULL pointer. ARRAY_SIZE(pdata->dcdc) is perfectly save because
sizeof only works on types so no actual dereference takes place.

Thanks,
Charles
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