[Buildroot] Kernel version

[Buildroot] Kernel version

[Zoran Djordjevic]

A problem with tslib - "selected device uses a different version of the event protocol than tslib was compiled for"
initiated me to rethink about item in Buildroot menu under "Kernel" subtree. 
What I don't understand is the meaning of Kernel version? (where I can enter for example 3.2.6) and custom kernel
configuration file - which could be ".config" from directory where are my linux sources (for example 2.6.32).
Questions are - how Buildroot knows where from to take kernel sources (is it directory where ".config" is ?) and 
what in that case means "Kernel version " item ? Which kernel is built - if 3.2.6 then where sources come from 
(Internet ?). Or is it only proper way to set "Kernel version" also?to 2.6.32 according to above examples, but in that 
case where the sources come from ?
?
Regards
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[Buildroot] Kernel version

[Arnout Vandecappelle]

On 09/24/12 22:11, Zoran Djordjevic wrote:
> A problem with tslib - "selected device uses a different version of the event protocol than tslib was compiled for"
> initiated me to rethink about item in Buildroot menu under "Kernel" subtree.
> What I don't understand is the meaning of Kernel version (where I can enter for example 3.2.6) and custom kernel
> configuration file - which could be ".config" from directory where are my linux sources (for example 2.6.32).
> Questions are - how Buildroot knows where from to take kernel sources (is it directory where ".config" is ?) and
> what in that case means "Kernel version " item ? Which kernel is built - if 3.2.6 then where sources come from
> (Internet ?). Or is it only proper way to set "Kernel version" alsoto 2.6.32 according to above examples, but in that
> case where the sources come from ?

  Hi Zoran,

  Since I don't understand what you mean with all of the above, I'll just explain
how things work.

  Buildroot downloads and compiles a linux kernel.  This kernel has nothing to
do with the kernel on your build machine - you could be building a 3.5 kernel
on a 2.4.32 build machine.  The kernel version that you specify in buildroot
is the version that will be downloaded from kernel.org.  If you have a custom
kernel source tree locally, you can use the CUSTOM_TARBALL or CUSTOM_GIT
options to build that one instead of a downloaded kernel.org tree.

  To build a kernel, you need a configuration file.  This can either be one of
the configuration files that are present in the kernel source itself (in the
arch/<arch>/configs directory), or a custom configuration file that you provide.
To create such a custom configuration file, you have two approaches:
- start from a kernel-provided configuration file for your platform, and tweak
it later.  Then you start with "use a defconfig", build the kernel, play around
with it.  Later, you run 'make linux-menuconfig' to modify the configuration,
build and test it again.  Finally, you change the buildroot configuration to
use a custom configuration file and set the filename to something that doesn't
exist yet.  Then, you run 'make linux-update-defconfig' to create the custom
configuration file.
- Instead of starting from a defconfig, you can also immediately start with
a custom configuration file.  You have to make sure it exists in this case,
but you can just do 'touch <filename>' to create it.  Then run
'make linux-menuconfig' and configure it as you like.


  Now, regarding the issue with tslib: that probably means that tslib was built
with kernel headers that are different from the kernel on which you are running.
Normally Linux tries to make sure that code compiled against old kernel headers
still works on newer kernels, but compiling against newer kernel headers and
running under an old kernel may be an issue.  I'm assuming you use a buildroot
toolchain (not ct-ng or an external toolchain): in that case, you can select
the kernel version to use for the kernel headers separately, under
Toolchain->Kernel Headers.  It doesn't go below 2.6.37, however.


  Regards,
  Arnout

-- 
Arnout Vandecappelle                               arnout at mind be
Senior Embedded Software Architect                 +32-16-286540
Essensium/Mind                                     http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium                BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F

[Buildroot] Kernel version

[Zoran Djordjevic]

?
I will try to be more specific and I am aware that host kernel version doesn't matter in this story. 
I have kernel sources for my board 2.6.32 on let' say "BoardKernelDir" directy. There, I also have ".config" file, for
kernel configuration.
Then I go into Buildroot menues (make menuconfig) and under "Kernel/Kernel version"
choose 3.2.6. In that same page of Buildroot menu, I can choose "Kernel configuration (Using custom configuration file)" 
to be the one I mentioned above (".config").
Question is - is it wrong procedure and what kernel will be built this way- the one from
"BoardKernelDir" (2.6.32) or 3.2.6 or (probably) it will make some mess ?
Also, can I somehow?(in Buildroot)?use sources for my board - not?those downloaded from kernel.org.
I intend to use CrosstoolNG.
Hope this is more clear.
?
Regard

? 

________________________________
 From: Arnout Vandecappelle <arnout@mind.be>
To: Zoran Djordjevic <djdjdjole@yahoo.com> 
Cc: "buildroot at busybox.net" <buildroot@busybox.net> 
Sent: Monday, September 24, 2012 11:24 PM
Subject: Re: [Buildroot] Kernel version
  
On 09/24/12 22:11, Zoran Djordjevic wrote:
> A problem with tslib - "selected device uses a different version of the event protocol than tslib was compiled for"
> initiated me to rethink about item in Buildroot menu under "Kernel" subtree.
> What I don't understand is the meaning of Kernel version (where I can enter for example 3.2.6) and custom kernel
> configuration file - which could be ".config" from directory where are my linux sources (for example 2.6.32).
> Questions are - how Buildroot knows where from to take kernel sources (is it directory where ".config" is ?) and
> what in that case means "Kernel version " item ? Which kernel is built - if 3.2.6 then where sources come from
> (Internet ?). Or is it only proper way to set "Kernel version" alsoto 2.6.32 according to above examples, but in that
> case where the sources come from ?

Hi Zoran,

Since I don't understand what you mean with all of the above, I'll just explain
how things work.

Buildroot downloads and compiles a linux kernel.? This kernel has nothing to
do with the kernel on your build machine - you could be building a 3.5 kernel
on a 2.4.32 build machine.? The kernel version that you specify in buildroot
is the version that will be downloaded from kernel.org.? If you have a custom
kernel source tree locally, you can use the CUSTOM_TARBALL or CUSTOM_GIT
options to build that one instead of a downloaded kernel.org tree.

To build a kernel, you need a configuration file.? This can either be one of
the configuration files that are present in the kernel source itself (in the
arch/<arch>/configs directory), or a custom configuration file that you provide.
To create such a custom configuration file, you have two approaches:
- start from a kernel-provided configuration file for your platform, and tweak
it later.? Then you start with "use a defconfig", build the kernel, play around
with it.? Later, you run 'make linux-menuconfig' to modify the configuration,
build and test it again.? Finally, you change the buildroot configuration to
use a custom configuration file and set the filename to something that doesn't
exist yet.? Then, you run 'make linux-update-defconfig' to create the custom
configuration file.
- Instead of starting from a defconfig, you can also immediately start with
a custom configuration file.? You have to make sure it exists in this case,
but you can just do 'touch <filename>' to create it.? Then run
'make linux-menuconfig' and configure it as you like.


Now, regarding the issue with tslib: that probably means that tslib was built
with kernel headers that are different from the kernel on which you are running.
Normally Linux tries to make sure that code compiled against old kernel headers
still works on newer kernels, but compiling against newer kernel headers and
running under an old kernel may be an issue.? I'm assuming you use a buildroot
toolchain (not ct-ng or an external toolchain): in that case, you can select
the kernel version to use for the kernel headers separately, under
Toolchain->Kernel Headers.? It doesn't go below 2.6.37, however.


Regards,
Arnout

-- Arnout Vandecappelle? ? ? ? ? ? ? ? ? ? ? ? ? ? ?  arnout at mind be
Senior Embedded Software Architect? ? ? ? ? ? ? ?  +32-16-286540
Essensium/Mind? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?  http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium? ? ? ? ? ? ? ? BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:? 7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F
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[Buildroot] Kernel version

[Arnout Vandecappelle]

On 09/25/12 09:29, Zoran Djordjevic wrote:
> I will try to be more specific and I am aware that host kernel version doesn't matter in this story.
> I have kernel sources for my board 2.6.32 on let' say "BoardKernelDir" directy. There, I also have ".config" file, for
> kernel configuration.
> Then I go into Buildroot menues (make menuconfig) and under "Kernel/Kernel version"
> choose 3.2.6. In that same page of Buildroot menu, I can choose "Kernel configuration (Using custom configuration file)"
> to be the one I mentioned above (".config").
> Question is - is it wrong procedure and what kernel will be built this way- the one from
> "BoardKernelDir" (2.6.32) or 3.2.6 or (probably) it will make some mess ?

  This will work, more or less.  It will download the 3.2.6 kernel and run its
configure with your 2.6.32 .config.  That will give you a lot of questions on
the console about config options which exist in the 3.2.6 kernel but didn't
exist yet in the 2.6.32 kernel.  So not necessarily the most efficient
approach.

> Also, can I somehow (in Buildroot) use sources for my board - not those downloaded from kernel.org.
> I intend to use CrosstoolNG.

  Yes you can: use the "custom tarball" option that I mentioned in my mail.

  You have to configure that separately for buildroot and for crosstool-NG.
AFAIK buildroot doesn't allow to give a directory, so you'll have to make
a tarball from the directory first.

  Regards,
  Arnout
-- 
Arnout Vandecappelle                               arnout at mind be
Senior Embedded Software Architect                 +32-16-286540
Essensium/Mind                                     http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium                BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F

[Buildroot] Kernel version

[Stephan Hoffmann]

Am 25.09.2012 09:29, schrieb Zoran Djordjevic:
>
> Also, can I somehow (in Buildroot) use sources for my board -
> not those downloaded from kernel.org.
>  
> Regard
>
You can use a local linux source tree with the source directory override
mechanism described here: http://free-electrons.com/blog/buildroot-2011-11/

Kind regards

Stephan

-- 
reLinux     -    Stephan Hoffmann
Am Schmidtgrund 124    50765 K?ln
Tel. +49.221.95595-19    Fax: -64
www.reLinux.de     sho at reLinux.de


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[Buildroot] Kernel version

[Zoran Djordjevic]

Forgive me for repeating my mail, because I forgot CC info in previous mail.
Now I correct that.
In that case, can you tell me your proposal regarding kernel versions and 
tslib problem. To remind you - my board has 2.6.32 kernel version and
I use Crosstool-NG.
What shoud I choose in Buildroot menu and also in Crosstool-NG menu ? 
Regards
 

________________________________
 From: Arnout Vandecappelle <arnout@mind.be>
To: Zoran Djordjevic <djdjdjole@yahoo.com> 
Cc: "buildroot at busybox.net" <buildroot@busybox.net> 
Sent: Tuesday, September 25, 2012 10:17 AM
Subject: Re: [Buildroot] Kernel version
  
On 09/25/12 09:29, Zoran Djordjevic wrote:
> I will try to be more specific and I am aware that host kernel version doesn't matter in this story.
> I have kernel sources for my board 2.6.32 on let' say "BoardKernelDir" directy. There, I also have ".config" file, for
> kernel configuration.
> Then I go into Buildroot menues (make menuconfig) and under "Kernel/Kernel version"
> choose 3.2.6. In that same page of Buildroot menu, I can choose "Kernel configuration (Using custom configuration file)"
> to be the one I mentioned above (".config").
> Question is - is it wrong procedure and what kernel will be built this way- the one from
> "BoardKernelDir" (2.6.32) or 3.2.6 or (probably) it will make some mess ?

This will work, more or less.? It will download the 3.2.6 kernel and run its
configure with your 2.6.32 .config.? That will give you a lot of questions on
the console about config options which exist in the 3.2.6 kernel but didn't
exist yet in the 2.6.32 kernel.? So not necessarily the most efficient
approach.

> Also, can I somehow (in Buildroot) use sources for my board - not those downloaded from kernel.org.
> I intend to use CrosstoolNG.

Yes you can: use the "custom tarball" option that I mentioned in my mail.

You have to configure that separately for buildroot and for crosstool-NG.
AFAIK buildroot doesn't allow to give a directory, so you'll have to make
a tarball from the directory first.

Regards,
Arnout
-- Arnout Vandecappelle? ? ? ? ? ? ? ? ? ? ? ? ? ? ?  arnout at mind be
Senior Embedded Software Architect? ? ? ? ? ? ? ?  +32-16-286540
Essensium/Mind? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?  http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium? ? ? ? ? ? ? ? BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:? 7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F
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[Buildroot] Kernel version

[Arnout Vandecappelle]

On 09/25/12 13:57, Zoran Djordjevic wrote:
> Forgive me for repeating my mail, because I forgot CC info in previous mail.
> Now I correct that.
> In that case, can you tell me your proposal regarding kernel versions and
> tslib problem. To remind you - my board has 2.6.32 kernel version and
> I use Crosstool-NG.
> What shoud I choose in Buildroot menu and also in Crosstool-NG menu ?

  If you have no need to rebuild the kernel, the easiest is to leave the kernel
build out of buildroot, and select the custom kernel dir option in crosstool-NG.

  Regards,
  Arnout
-- 
Arnout Vandecappelle                               arnout at mind be
Senior Embedded Software Architect                 +32-16-286540
Essensium/Mind                                     http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium                BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F