linux-kernel - Re: Linux 2.6.26-rc1

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Date:	Wed, 07 May 2008 01:36:09 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
CC:	Alistair John Strachan <alistair@...zero.co.uk>,
	Robin Holt <holt@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.26-rc1

Mauro Carvalho Chehab wrote:
> On Tue, 06 May 2008 22:47:20 +0200
> Stefan Richter <stefanr@...6.in-berlin.de> wrote:
>> Or another idea:
>>
>> Copy _all_ dependencies of drivers which can be selected by "...if 
    ^^^^
>> VIDEO_HELPER_CHIPS_AUTO" to VIDEO_HELPER_CHIPS_AUTO.
> 
> I actually did this for tuners, on this changeset (still not at mainstream):
> http://git.kernel.org/?p=linux/kernel/git/mchehab/v4l-dvb.git;a=commitdiff;h=d10b3c6817fb3fed8e6cd6d64d47c187a615c952

Yes...  Except that it is very dangerous to /move/ dependencies, as you 
are apparently doing in that patch.  When you use "select" somewhere, 
you should generally /copy/ dependencies.

Although something like

config VIRTUAL_META_OPTION
	depends on REAL_DEPENDENCY

config THE_REAL_THING
	depends on VIRTUAL_META_OPTION

does work if THE_REAL_THING actually depends on REAL_DEPENDENCY, it is 
safer if this dependency stays there, i.e.

config THE_REAL_THING
	depends on REAL_DEPENDECY

or

config THE_REAL_THING
	depends on REAL_DEPENDENCY && VIRTUAL_META_OPTION

or whatever, or equivalent constructs involving "if"..."endif".

(I presume that for example MEDIA_TUNER_TDA827X does indeed have a build 
dependency on DVB_CORE && I2C.)

Or in other words:

Since MEDIA_TUNER selects a bunch of options which itself have build 
dependencies, you /must/ duplicate all of their dependencies to 
MEDIA_TUNER.  Well, actually you don't use plain "select", you use 
"select ... if !MEDIA_TUNER_CUSTOMIZE".  So if you can ensure by other 
means that those 2nd level dependencies are guaranteed to be fulfilled 
whenever MEDIA_TUNER_CUSTOMIZE=n, then you don't need to duplicate the 
2nd level dependencies into MEDIA_TUNER.

That's the same what I meant in my comment on VIDEO_HELPER_CHIPS_AUTO:

Those options which "select" video decoders generally /must/ contain 
duplicates of the dependency statements of the decoders which they 
select.  Except, since you don't use plain "select" there but actually 
"select ... if VIDEO_HELPER_CHIPS_AUTO", you can alternatively put the 
duplicates of the dependency statements to VIDEO_HELPER_CHIPS_AUTO.
-- 
Stefan Richter
-=====-==--- -=-= --===
http://arcgraph.de/sr/
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