linux-kernel - Re: [PATCH v2] regulator: s2mps11: Simplify expression used in BUILD_BUG

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Message-id: <56C522F7.5040109@samsung.com>
Date:	Thu, 18 Feb 2016 10:48:39 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Andi Shyti <andi.shyti@...sung.com>
Cc:	Sangbeom Kim <sbkim73@...sung.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, jacob.e.keller@...el.com,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2] regulator: s2mps11: Simplify expression used in
 BUILD_BUG_ON

On 18.02.2016 10:46, Andi Shyti wrote:
>>>> Following BUILD_BUG_ON using a variable fails for some of the compilers
>>>> and optimization levels (reported for gcc 4.9):
>>>> 	var = ARRAY_SIZE(s2mps15_regulators);
>>>> 	BUILD_BUG_ON(S2MPS_REGULATOR_MAX < var);
>>>> Fix this by using ARRAY_SIZE directly.
>>>>
>>>> Additionally add missing BUILD_BUG_ON check for S2MPS15 device (the
>>>> check ensures that internal arrays are big enough to hold data for all
>>>> of regulators on all devices).
>>>>
>>>> Reported-by: Arnd Bergmann <arnd@...db.de>
>>>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
>>>>
>>>
>>> [...]
>>>
>>>>  	case S2MPS11X:
>>>>  		s2mps11->rdev_num = ARRAY_SIZE(s2mps11_regulators);
>>>
>>> Why don't we remove rdev_num at all? It's not used that much
>>> other than in the probe function.
>>
>> Remove from probe? It is used in probe and removal would make the code
>> more complicated than it should be.
> 
> no, I mean remove it from s2mps11_info. Other than in the probe
> this value is used only once in s2mps11_pmic_dt_parse() (which is
> called by probe()).

Sure, it can be safely removed from s2mps11_info... but it won't affect
this issue and this patch. Still the local variable would be used in
probe leading to compiler optimization choices impacting BUILD_BUG_ON.

BR,
Krzysztof