how can i figure out where a particular kernel config option came from?

how can i figure out where a particular kernel config option came from?

[Robert P. J. Day]

  short version: with a short BSP layer i've been handed, the eventual
kernel .config file ends up with the setting:

  CONFIG_WIRELESS=y

which makes no sense as the target board has no wireless and the BSP
itself doesn't set that, so how can i start tracking back to figure
out where that particular setting came from?

  long version: i'm actually using Wind River Linux 7, but the
question remains the same. it turns out that CONFIG_WIRELESS is
selected by CONFIG_WLAN, so i'm really after what sets CONFIG_WLAN. i
don't see it in the BSP layer, so i'm tracing back to the WR kernel
recipe, and possibly features templates and any other kernel .cfg
snippets i can find, so far with no luck.

  in either case, is there a log file that lists *precisely* which
kernel config snippets contributed to the final .config file? thanks.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: how can i figure out where a particular kernel config option came from?

[Bruce Ashfield]

On 12/09/2015 05:36 AM, Robert P. J. Day wrote:
>
>    short version: with a short BSP layer i've been handed, the eventual
> kernel .config file ends up with the setting:
>
>    CONFIG_WIRELESS=y
>
> which makes no sense as the target board has no wireless and the BSP
> itself doesn't set that, so how can i start tracking back to figure
> out where that particular setting came from?
>
>    long version: i'm actually using Wind River Linux 7, but the
> question remains the same. it turns out that CONFIG_WIRELESS is
> selected by CONFIG_WLAN, so i'm really after what sets CONFIG_WLAN. i
> don't see it in the BSP layer, so i'm tracing back to the WR kernel
> recipe, and possibly features templates and any other kernel .cfg
> snippets i can find, so far with no luck.
>
>    in either case, is there a log file that lists *precisely* which
> kernel config snippets contributed to the final .config file? thanks.

The meta-series in the kernel source directory has all the details.
If you locate the kernel source for your build, it'll be in a 'meta'
or '.meta' directory (depending on the version of the tools), and be
called ... 'meta-series'.

Bruce

>
> rday
>

Re: how can i figure out where a particular kernel config option came from?

[Robert P. J. Day]

On Wed, 9 Dec 2015, Bruce Ashfield wrote:

> On 12/09/2015 05:36 AM, Robert P. J. Day wrote:
> >
> >    short version: with a short BSP layer i've been handed, the eventual
> > kernel .config file ends up with the setting:
> >
> >    CONFIG_WIRELESS=y
> >
> > which makes no sense as the target board has no wireless and the BSP
> > itself doesn't set that, so how can i start tracking back to figure
> > out where that particular setting came from?
> >
> >    long version: i'm actually using Wind River Linux 7, but the
> > question remains the same. it turns out that CONFIG_WIRELESS is
> > selected by CONFIG_WLAN, so i'm really after what sets CONFIG_WLAN. i
> > don't see it in the BSP layer, so i'm tracing back to the WR kernel
> > recipe, and possibly features templates and any other kernel .cfg
> > snippets i can find, so far with no luck.
> >
> >    in either case, is there a log file that lists *precisely* which
> > kernel config snippets contributed to the final .config file? thanks.
>
> The meta-series in the kernel source directory has all the details.
> If you locate the kernel source for your build, it'll be in a 'meta'
> or '.meta' directory (depending on the version of the tools), and be
> called ... 'meta-series'.

  *sigh* ... i was already poring through that file when it occurred
that there might be a simpler answer -- perhaps the Kbuild structure
set wireless to 'y' by default and, sure enough, right there in
net/Kconfig:


menuconfig WIRELESS
        bool "Wireless"
        depends on !S390
        default y

if WIRELESS

source "net/wireless/Kconfig"
source "net/mac80211/Kconfig"

endif # WIRELESS


  argh, i thought to myself, what short-sighted tool decided that
wireless should be selected by default?

5442060c0 (Robert P. J. Day                2008-07-24 12:20:09 -0400 346) menuconfig WIRELESS
5442060c0 (Robert P. J. Day                2008-07-24 12:20:09 -0400 347)       bool "Wireless"
f54bfc0e3 (Martin Schwidefsky              2007-05-10 15:46:01 +0200 348)       depends on !S390
5442060c0 (Robert P. J. Day                2008-07-24 12:20:09 -0400 349)       default y
5442060c0 (Robert P. J. Day                2008-07-24 12:20:09 -0400 350)
5442060c0 (Robert P. J. Day                2008-07-24 12:20:09 -0400 351) if WIRELESS


  i'm going back to bed.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================