linux-kernel - Re: [RFC PATCH 4/8] misc: emif: add basic infrastructure for EMIF driver

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Date:	Fri, 17 Feb 2012 14:44:45 +0100
From:	"Cousson, Benoit" <b-cousson@...com>
To:	Aneesh V <aneesh@...com>
CC:	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 4/8] misc: emif: add basic infrastructure for EMIF
 driver

Hi Aneesh,

On 2/17/2012 2:26 PM, Aneesh V wrote:
> On Thursday 16 February 2012 10:00 PM, Cousson, Benoit wrote:
>> On 2/4/2012 1:16 PM, Aneesh V wrote:

[...]

>>> +/**
>>> + * struct emif_data - Per device static data for driver's use
>>> + * @duplicate: Whether the DDR devices attached to this EMIF
>>> + * instance are exactly same as that on EMIF1. In
>>> + * this case we can save some memory and processing
>>> + * @temperature_level: Maximum temperature of LPDDR2 devices attached
>>> + * to this EMIF - read from MR4 register. If there
>>> + * are two devices attached to this EMIF, this
>>> + * value is the maximum of the two temperature
>>> + * levels.
>>> + * @irq: IRQ number
>>
>> Do you really need to store the IRQ number?
>
> Yes, I need it right now because setup_interrupts() is called later,
> after the first frequency notification, because that's when I have the
> registers to be programmed on a temperature event. But I am re-thinking
> on this strategy. I will move it back to probe() because other
> interrupts can/should be enabled at probe() time. When I do that I
> won't have to store it anymore and I will remove it.

Yes, I saw the code in a later patch. But in that case you should have 
introduced that attribute in the patch that will use it and not before.

But I do agree, that requesting the interrupt in the probe is probably 
better.

[...]

>>> + emif = kzalloc(sizeof(struct emif_data), GFP_KERNEL);
>>
>> You should use the devm_* version of this API to get the simplify the
>> error handling / removal.
>
> Please note that most of my allocations are happening through
> kmemdup(). kmemdup() doesn't have a devm_* equivalent. So, I have a
> cleanup() function and in the interest of uniformity decided to avoid
> devm_* variants altogether.

I think it still worth using devm_kzalloc + memcopy here instead of 
kmemdup to avoid the cleanup() and simplify as well the error handling.

You might even propose a new devm_kmemdup API if you want.

Regards,
Benoit
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