linux-kernel - Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for 'devm_ioremap

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Message-ID: <53C47B76.4080306@roeck-us.net>
Date:	Mon, 14 Jul 2014 17:53:10 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Chen Gang <gang.chen.5i5j@...il.com>,
	Richard Weinberger <richard@....at>
CC:	Lars-Peter Clausen <lars@...afoo.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	dmitry.torokhov@...il.com, linux-iio@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>, teg@...m.no,
	Thierry Reding <thierry.reding@...il.com>,
	Lennox Wu <lennox.wu@...il.com>, Marek Vasut <marex@...x.de>,
	Liqin Chen <liqin.linux@...il.com>, msalter@...hat.com,
	linux-pwm@...r.kernel.org, devel@...verdev.osuosl.org,
	linux-watchdog@...r.kernel.org, linux-input@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	knaack.h@....de, Martin Schwidefsky <schwidefsky@...ibm.com>,
	Mischa.Jonker@...opsys.com, jic23@...nel.org, arnd@...db.de,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for
 'devm_ioremap_resource'

On 07/14/2014 05:34 PM, Chen Gang wrote:
> On 07/14/2014 05:22 PM, Chen Gang wrote:
>>
>> 在 2014年7月14日，下午4:57，Richard Weinberger <richard@....at> 写道：
>>
>>> Am 14.07.2014 10:48, schrieb Lars-Peter Clausen:
>>>> On 07/14/2014 10:31 AM, Richard Weinberger wrote:
>>>>> Am 13.07.2014 22:17, schrieb Greg Kroah-Hartman:
>>>>>> On Sun, Jul 13, 2014 at 09:33:38PM +0200, Richard Weinberger wrote:
>>>>>>> Maybe we could add COMPILE_TEST to the version string too?
>>>>>>> Just to detect such kernels fast in user bug reports...
>>>>>>
>>>>>> What kind of bug report are you going to get?
>>>>>
>>>>> User manages to enable CONFIG_FOO by selecting COMPILE_TEST and
>>>>> complains that it does not work. :)
>>>>
>>>> These drivers are typically drivers for some SoC peripheral and the device will simply physically not exist on a platform that does not provide HAS_IOMEM. This is not really any
>>>> different from making the driver selectable via COMPILE_TEST for any other platform. To hit the issue you'd have to instantiate a device driver instance for a device that
>>>> physically does not exist. This will always result in a failure.
>>>
>>> Okay, you have convinced me. :)
>>>
>
> After search the history patches, I found one related patch which made
> by myself (when I am in Asianux):
>
>    "https://lkml.org/lkml/2013/7/1/641"
>
> For me, it is a long discussion, and forced many members have to join
> in. Please help check again.
>

One thing you could try would be to return NULL (or where appropriate
an error) in the #else case of CONFIG_HAS_IOMEM and CONFIG_HAS_IOPORT,
ie dont take COMPILE_TEST into account at all. Obviously that means
you won't be able to dump a warning message in the COMPILE_TEST
case, but at least the code would compile. The rejection of above patch
would make a good case for this approach.

Guenter

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