linux-kernel - Re: [PATCH] gpio: palmas: add dt support

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Date:	Tue, 2 Apr 2013 11:01:14 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Stephen Warren <swarren@...dia.com>
Cc:	Laxman Dewangan <ldewangan@...dia.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] gpio: palmas: add dt support

On Thu, Mar 28, 2013 at 3:55 PM, Stephen Warren <swarren@...dia.com> wrote:
> On 03/27/2013 11:59 PM, Laxman Dewangan wrote:
>> On Wednesday 27 March 2013 06:30 PM, Linus Walleij wrote:
>>> On Thu, Mar 21, 2013 at 3:30 PM, Laxman Dewangan
>>> <ldewangan@...dia.com> wrote:
>>>
>>>> +#ifdef CONFIG_OF
>>>> +static struct of_device_id of_palmas_gpio_match[] = {
>>>> +       { .compatible = "ti,palmas-gpio"},
>>>> +       { },
>>>> +};
>>>> +MODULE_DEVICE_TABLE(of, of_palmas_gpio_match);
>>>> +#endif
>>>
>>> But please drop the #ifdef here unless it causes compile errors
>>> (I don't think it will.)
>>>
>>
>> I am using this table as
>>
>> driver.of_match_table = of_match_ptr(of_palmas_gpio_match),
>> of_match_ptr is macro which is NULL in case of CONFIG_OF not defined.
>> So if I remove ifdefs then it may create build warning as unused variable.
>
> I think Linus's point is that you can simply remove the use of
> of_match_ptr(). The only disadvantage of doing so is that the table will
> always be included in the object file, but it's so small that it's
> probably not worth worrying about.

Oh I wasn't that smart :-)

But what you're saying seems true.

The of_match_ptr() is something
I haven't quite seen before and don't quite understand the
semantics of, why would we use that?

Yours,
Linus Walleij
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