linux-kernel - RE: [PATCH 1/5] arch/arm: Correct NULL test

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Date:	Mon, 28 Dec 2009 12:09:04 -0500
From:	"H Hartley Sweeten" <hartleys@...ionengravers.com>
To:	"Julia Lawall" <julia@...u.dk>
Cc:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	<kernel-janitors@...r.kernel.org>, <linux@....linux.org.uk>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH 1/5] arch/arm: Correct NULL test

On Monday, December 28, 2009 9:51 AM, Julia Lawall wrote:
> On Mon, 28 Dec 2009, H Hartley Sweeten wrote:
>
>> On Sunday, December 27, 2009 3:08 PM, Julia Lawall wrote:
>>>>>  	dbgfs_chan = kmalloc(sizeof(*dbgfs_state) * num_dma_channels,
>>>>>  			     GFP_KERNEL);
>>>>> -	if (!dbgfs_state)
>>>>> +	if (!dbgfs_chan)
>>>>>  		goto err_alloc;
>>>> Shouldn't the malloc line read:
>>>> 
>>>> 	... = kmalloc(sizeof(*dbgfs_chan) * ...)
>>>> 	                      ^^^^^^^^^^
>>>> 
>>>> ?
>>>
>>> Good point, thanks.  I will send a revised patch.
>> 
>> Wouldn't this be clearer?
>> 
>> 	... = kmalloc(sizeof(struct dentry) * ...)
>
> Documentation/CodingStyle thinks otherwise:
>
> "The preferred form for passing a size of a struct is the following:
>
> 	p = kmalloc(sizeof(*p), ...);
>
> The alternative form where struct name is spelled out hurts readability 
> and introduces an opportunity for a bug when the pointer variable type is 
> changed but the corresponding sizeof that is passed to a memory allocator 
> is not."
>
> And actually, in this case, sizeof(struct dentry) would be wrong, because 
> the type of dbgfs_chan is struct dentry **, not struct dentry *.  What is 
> wanted is an array of pointers.

Ah, missed that.  Thanks for pointing it out.

Regards,
Hartley
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