linux-kernel - Re: RFC: kconfig select warnings bogus?

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Date:	Tue, 22 May 2007 19:03:03 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Satyam Sharma <satyam.sharma@...il.com>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Roman Zippel <zippel@...ux-m68k.org>,
	Kumar Gala <galak@...nel.crashing.org>,
	Simon Horman <horms@...ge.net.au>,
	Adrian Bunk <bunk@...sta.de>, Sam Ravnborg <sam@...nborg.org>
Subject: Re: RFC: kconfig select warnings bogus?

Satyam Sharma wrote:
> On 5/20/07, Stefan Richter <stefanr@...6.in-berlin.de> wrote:
>> > On 5/20/07, Stefan Richter <stefanr@...6.in-berlin.de> wrote:
>> >> config A
>> >>         bool-or-tristate "option A"
>> >>         depends on !PLATFORM_X || HELPER_N_ON_PLATFORM_X
[...]
> Umm, if A requires helper code N (which is available only on platform X),
[And, I assumed, 'A' works without helper 'N' on all platforms except
'X'.  This is a synthetic example which might not have a real-world
application.]
> then why/how do we want A to depend on platforms _other_ than X?

The expression means:  'A' can be enabled on all platforms.  Except on
platform_X, there it can only be enabled if helper_N is built too.

[...]
>>         depends on PM
>>         depends on SWAP
>>         depends on (X86 && !SMP) ||
>>                    (X86 && SUSPEND_SMP) ||
>>                    (PPC64_SWSUSP && !SMP) ||
>>                    (PPC64_SWSUSP && SUSPEND_SMP) ||
>>                    (FRV   && !SMP) ||
>>                    (PPC32 && !SMP)
> 
> Ok, so perhaps you actually meant X && N_ON_X above.

No.  I meant "(X && N_ON_X) || Any_one_platform_other_than_X" above.

The 2nd example is a whitelist, while the 1st example is some kind of
blacklist.  A real-world example of blacklist style:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=a73df4dfdb0e01a1cbf119416a00e520a5e22306
(Lived only 2 days in Linus' tree.)
-- 
Stefan Richter
-=====-=-=== -=-= =-==-
http://arcgraph.de/sr/
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