Message-ID: <51D37DD6.50305@asianux.com>
Date:	Wed, 03 Jul 2013 09:26:46 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Richard Weinberger <richard@....at>, Arnd Bergmann <arnd@...db.de>,
	Jeff Dike <jdike@...toit.com>,
	David Sharp <dhsharp@...gle.com>,
	"sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>,
	uml-user <user-mode-linux-user@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <trivial@...nel.org>
Subject: Re: [PATCH] include/asm-generic/io.h: add dummy fuctions to support
 'COMPILE_TEST' in 'asm-generic'.

On 07/03/2013 08:51 AM, Chen Gang wrote:
> On 07/02/2013 06:57 PM, Geert Uytterhoeven wrote:
>> On Tue, Jul 2, 2013 at 10:00 AM, Chen Gang <gang.chen@...anux.com> wrote:
>>>> On 07/02/2013 03:19 PM, Geert Uytterhoeven wrote:
>>>>>> On Tue, Jul 2, 2013 at 4:13 AM, Chen Gang <gang.chen@...anux.com> wrote:
>>>>>>>>>> 'asm-generic' need provide necessary configuration checking, if can't
>>>>>>>>>> pass checking, 'asm-generic' shouldn't implement it.
>>>>>>>>>>
>>>>>>>>>> For 'COMPILE_TEST', according to its help contents, 'asm-generic' need
>>>>>>>>>> let it pass configuration checking, and provide related dummy contents
>>>>>>>>>> for it.
>>>>>>>>>>
>>>>>>>>>> Part of 'COMPLE_TEST' help contents in "init/Kconfig":
>>>>>>>>>>
>>>>>>>>>>   "...Despite they cannot be loaded there (or even when they load they cannot be used due to missing HW support)..."
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Chen Gang <gang.chen@...anux.com>
>>>>>> NAKed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>>>>>>
>>>>>> Please don't clutter the code with checks for CONFIG_COMPILE_TEST.
>>>>
>>>> Do you mean: 'asm-generic' should not support 'COMPILE_TEST' (the
>>>> platform should not support 'COMPILE_TEST") ?
>>>>
>>>> Or you mean: 'COMPILE_TEST' should not exist in kernel ?
>> I mean that COMPILE_TEST should exist in Kconfig files only.
>> It's only meant to have more compile coverage, not to "fix" (through #ifdef)
>> more code to make it compile.
> 
> If so, can we allow the module to 'COMPILE_TEST' under one platform
> which not support the related HW ?
> 
>   e.g. "...Despite they cannot be loaded there (or even when they load
> they cannot be used due to missing HW support)...".
> 
> 
> 'asm-generic' need provide generic layer to users (both architecture
> guys and module guys).
> 
> So for 'default', it can depend on some conditions (e.g. HW support);
> but for 'generic', it need try to be independent from any conditions.
> 
> And it is also necessary for 'generic' to provide the configuration
> checking features, but this checking must be no negative effect (or
> consistent) with its 'generic' services.
> 
> So it is necessary to check 'NOMMU', 'CONFIG_HAS_IOMEM' ..., but it
> also necessary to consider about 'COMPILE_TEST' to be consistent with
> its 'generic' services.
> 
> 
> BTW: 20% code are for 80% features, but the left 20% features, need 80%
> code, if we have to make it complete, we have to face this 'rule'.
> 
> 

It is necessary to let the 'COMPILE_TEST' related members to know about
it (better to provide their own opinions), it may be helpful for our
discussion, so I list the details below.

-------------------------------commit begin----------------------------------

commit 4bb1667255a86360721291fe59991d033bbc2f2a
Author: Jiri Slaby <jslaby@...e.cz>
Date:   Wed May 22 10:56:24 2013 +0200

    build some drivers only when compile-testing
    
    Some drivers can be built on more platforms than they run on. This is
    a burden for users and distributors who package a kernel. They have to
    manually deselect some (for them useless) drivers when updating their
    configs via oldconfig. And yet, sometimes it is even impossible to
    disable the drivers without patching the kernel.
    
    Introduce a new config option COMPILE_TEST and make all those drivers
    to depend on the platform they run on, or on the COMPILE_TEST option.
    Now, when users/distributors choose COMPILE_TEST=n they will not have
    the drivers in their allmodconfig setups, but developers still can
    compile-test them with COMPILE_TEST=y.
    
    Now the drivers where we use this new option:
    * PTP_1588_CLOCK_PCH: The PCH EG20T is only compatible with Intel Atom
      processors so it should depend on x86.
    * FB_GEODE: Geode is 32-bit only so only enable it for X86_32.
    * USB_CHIPIDEA_IMX: The OF_DEVICE dependency will be met on powerpc
      systems -- which do not actually support the hardware via that
      method.
    * INTEL_MID_PTI: It is specific to the Penwell type of Intel Atom
      device.
    
    [v2]
    * remove EXPERT dependency
    
    [gregkh - remove chipidea portion, as it's incorrect, and also doesn't
     apply to my driver-core tree]
    
     Signed-off-by: Jiri Slaby <jslaby@...e.cz>
    Cc: Andrew Morton <akpm@...ux-foundation.org>
    Cc: Linus Torvalds <torvalds@...ux-foundation.org>
    Cc: Jeff Mahoney <jeffm@...e.com>
    Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
    Cc: linux-usb@...r.kernel.org
    Cc: Florian Tobias Schandinat <FlorianSchandinat@....de>
    Cc: linux-geode@...ts.infradead.org
    Cc: linux-fbdev@...r.kernel.org
    Cc: Richard Cochran <richardcochran@...il.com>
    Cc: netdev@...r.kernel.org
    Cc: Ben Hutchings <ben@...adent.org.uk>
    Cc: "Keller, Jacob E" <jacob.e.keller@...el.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

diff --git a/init/Kconfig b/init/Kconfig
index 55ccdf6..1e825c2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -53,6 +53,20 @@ config CROSS_COMPILE
          need to set this unless you want the configured kernel build
          directory to select the cross-compiler automatically.
 
+config COMPILE_TEST
+       bool "Compile also drivers which will not load"
+       default n
+       help
+         Some drivers can be compiled on a different platform than they are
+         intended to be run on. Despite they cannot be loaded there (or even
+         when they load they cannot be used due to missing HW support),
+         developers still, opposing to distributors, might want to build such
+         drivers to compile-test them.
+
+         If you are a developer and want to build everything available, say Y
+         here. If you are a user/distributor, say N here to exclude useless
+         drivers to be distributed.
+

-------------------------------commit end------------------------------------

Thanks.
-- 
Chen Gang
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