[5/9] manual: faq: add workaround to avoid rebuilding the buildroot toolchain after each clean

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
---
 docs/manual/common-usage.txt        |  1 +
 docs/manual/faq-troubleshooting.txt | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

On 13/02/13 23:59, Samuel Martin wrote:
>
> Signed-off-by: Samuel Martin <s.martin49@gmail.com>
> ---
>   docs/manual/common-usage.txt        |  1 +
>   docs/manual/faq-troubleshooting.txt | 34 ++++++++++++++++++++++++++++++++++
>   2 files changed, 35 insertions(+)
>
> diff --git a/docs/manual/common-usage.txt b/docs/manual/common-usage.txt
> index c7f511a..b36965f 100644
> --- a/docs/manual/common-usage.txt
> +++ b/docs/manual/common-usage.txt
> @@ -20,6 +20,7 @@ all sources that you previously selected in the configurator
>   You can now disconnect or copy the content of your +dl+
>   directory to the build-host.
>
> +[[daily-oot-build]]
>   Building out-of-tree
>   ~~~~~~~~~~~~~~~~~~~~

  The other tags in this section don't have the 'daily-' prefix, and it 
took me a while to understand what the daily meant in the first place. So 
I'd rename it to out-of-tree-build.

>
> diff --git a/docs/manual/faq-troubleshooting.txt b/docs/manual/faq-troubleshooting.txt
> index 8b0882a..f367275 100644
> --- a/docs/manual/faq-troubleshooting.txt
> +++ b/docs/manual/faq-troubleshooting.txt
> @@ -147,3 +147,37 @@ Using the internal Buildroot toolchain backend
>   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>   These toolchains are currently *not relocatable*.
> +
> +However, it is possible to build a toolchain using the internal Buildroot
> +backend in another location (see xref:daily-oot-build[]), then use it as an
> +_external_ one to prevent from rebuilding it after issuing +make clean+
> +(see xref:faq-avoid-rebuild-toolchain[]).

  xreffing to immediately below is a bit silly...

> +
> +[[faq-avoid-rebuild-toolchain]]
> +How to avoid always rebuilding the toolchain?
> +---------------------------------------------
> +
> +When using the internal Buildroot toolchain backend or the
> +http://crosstool-ng.org[crosstool-NG] one, runnong +make clean+ not only
                                               ^^^^^^^ running

> +remove the built binaries, but also the whole toolchain.
> +
> +It is possible to prevent this by, first, building the toolchain in a
> +place different from the one  where the images will be built.

  The 'first' sounds a bit strange here. How about:

It is possible to prevent this by building the toolchain in a different 
place than the one where the images will be built. To do so:

> +
> +To do so:
> +
> +1. Build the toolchain somewhere:
> ++
> +----------------------------
> +make toolchain O=/path/to/toolchain

  I personally would do it with

make toolchain BR2_HOST_DIR=/path/to/toolchain

  That gives you everything you need and nothing more (no build dir and 
stuff).

> +----------------------------
> ++
> +1. Use this pre-built toolchain as an external one in a new and clean
> +   build (see xref:external-toolchain-backend[]) with a different output
> +   directory than the pre-built toolchain one.

  Not clear enough. How about:

1. Reconfigure buildroot with a custom external toolchain (see
xref:external-toolchain-backend[]). Set the toolchain path to
`/path/to/toolchain/usr`.

// Note: that's actually not a good example, because the default for
// BR2_TOOLCHAIN_EXTERNAL_PATH is literally /path/to/toolchain/usr, so a
// dumb user could think it is already correct...]

1. `make clean; make`

> +
> +This way, you will not have to rebuild the toolchain after invoking
> ++make clean+.
> +
> +However, the toolchain should be regenerated after any change of the
> ++Target Architecture+ (or its _variant_), or done in the +Toolchain+ menu.

However, the toolchain should be regenerated after you change a target 
architecture option (architecture variant, ABI, floating point, ...), or 
when you make any change in the +Toolchain+ menu.


  Regards,
  Arnout

Dear Samuel Martin,

On Wed, 13 Feb 2013 23:59:06 +0100, Samuel Martin wrote:
> 
> Signed-off-by: Samuel Martin <s.martin49@gmail.com>
> ---
>  docs/manual/common-usage.txt        |  1 +
>  docs/manual/faq-troubleshooting.txt | 34 ++++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/docs/manual/common-usage.txt b/docs/manual/common-usage.txt
> index c7f511a..b36965f 100644
> --- a/docs/manual/common-usage.txt
> +++ b/docs/manual/common-usage.txt
> @@ -20,6 +20,7 @@ all sources that you previously selected in the configurator
>  You can now disconnect or copy the content of your +dl+
>  directory to the build-host.
>  
> +[[daily-oot-build]]
>  Building out-of-tree
>  ~~~~~~~~~~~~~~~~~~~~
>  
> diff --git a/docs/manual/faq-troubleshooting.txt b/docs/manual/faq-troubleshooting.txt
> index 8b0882a..f367275 100644
> --- a/docs/manual/faq-troubleshooting.txt
> +++ b/docs/manual/faq-troubleshooting.txt
> @@ -147,3 +147,37 @@ Using the internal Buildroot toolchain backend
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  
>  These toolchains are currently *not relocatable*.
> +
> +However, it is possible to build a toolchain using the internal Buildroot
> +backend in another location (see xref:daily-oot-build[]), then use it as an
> +_external_ one to prevent from rebuilding it after issuing +make clean+
> +(see xref:faq-avoid-rebuild-toolchain[]).
> +
> +[[faq-avoid-rebuild-toolchain]]
> +How to avoid always rebuilding the toolchain?
> +---------------------------------------------
> +
> +When using the internal Buildroot toolchain backend or the
> +http://crosstool-ng.org[crosstool-NG] one, runnong +make clean+ not only
> +remove the built binaries, but also the whole toolchain.
> +
> +It is possible to prevent this by, first, building the toolchain in a
> +place different from the one  where the images will be built.
> +
> +To do so:
> +
> +1. Build the toolchain somewhere:
> ++
> +----------------------------
> +make toolchain O=/path/to/toolchain
> +----------------------------
> ++
> +1. Use this pre-built toolchain as an external one in a new and clean
> +   build (see xref:external-toolchain-backend[]) with a different output
> +   directory than the pre-built toolchain one.
> +
> +This way, you will not have to rebuild the toolchain after invoking
> ++make clean+.
> +
> +However, the toolchain should be regenerated after any change of the
> ++Target Architecture+ (or its _variant_), or done in the +Toolchain+ menu.

I think this text is misleading, because it suggests that the only way
to avoid rebuilding the toolchain over and over again is to build a
toolchain with Buildroot, and then use it as an external toolchain in
Buildroot. There are other options that are possible:
 * Use Crosstool-NG outside of Buildroot to generate a toolchain
 * Use a pre-built toolchain

I have the feeling that this new text doesn't articulate very well with
the text that was added in 401d323698266468e322471530ee1997835fc335.

We have to be careful to not add a set of random facts in the manual
one after the other, without keeping a consistency and ordering on the
different parts of the manual.

Thomas

Hi Thomas,

2013/2/14 Thomas Petazzoni <thomas.petazzoni@free-electrons.com>:
> Dear Samuel Martin,
>
> On Wed, 13 Feb 2013 23:59:06 +0100, Samuel Martin wrote:
>>
>> Signed-off-by: Samuel Martin <s.martin49@gmail.com>
>> ---
>>  docs/manual/common-usage.txt        |  1 +
>>  docs/manual/faq-troubleshooting.txt | 34 ++++++++++++++++++++++++++++++++++
>>  2 files changed, 35 insertions(+)
>>
>> diff --git a/docs/manual/common-usage.txt b/docs/manual/common-usage.txt
>> index c7f511a..b36965f 100644
>> --- a/docs/manual/common-usage.txt
>> +++ b/docs/manual/common-usage.txt
>> @@ -20,6 +20,7 @@ all sources that you previously selected in the configurator
>>  You can now disconnect or copy the content of your +dl+
>>  directory to the build-host.
>>
>> +[[daily-oot-build]]
>>  Building out-of-tree
>>  ~~~~~~~~~~~~~~~~~~~~
>>
>> diff --git a/docs/manual/faq-troubleshooting.txt b/docs/manual/faq-troubleshooting.txt
>> index 8b0882a..f367275 100644
>> --- a/docs/manual/faq-troubleshooting.txt
>> +++ b/docs/manual/faq-troubleshooting.txt
>> @@ -147,3 +147,37 @@ Using the internal Buildroot toolchain backend
>>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>>  These toolchains are currently *not relocatable*.
>> +
>> +However, it is possible to build a toolchain using the internal Buildroot
>> +backend in another location (see xref:daily-oot-build[]), then use it as an
>> +_external_ one to prevent from rebuilding it after issuing +make clean+
>> +(see xref:faq-avoid-rebuild-toolchain[]).
>> +
>> +[[faq-avoid-rebuild-toolchain]]
>> +How to avoid always rebuilding the toolchain?
>> +---------------------------------------------
>> +
>> +When using the internal Buildroot toolchain backend or the
>> +http://crosstool-ng.org[crosstool-NG] one, runnong +make clean+ not only
>> +remove the built binaries, but also the whole toolchain.
>> +
>> +It is possible to prevent this by, first, building the toolchain in a
>> +place different from the one  where the images will be built.
>> +
>> +To do so:
>> +
>> +1. Build the toolchain somewhere:
>> ++
>> +----------------------------
>> +make toolchain O=/path/to/toolchain
>> +----------------------------
>> ++
>> +1. Use this pre-built toolchain as an external one in a new and clean
>> +   build (see xref:external-toolchain-backend[]) with a different output
>> +   directory than the pre-built toolchain one.
>> +
>> +This way, you will not have to rebuild the toolchain after invoking
>> ++make clean+.
>> +
>> +However, the toolchain should be regenerated after any change of the
>> ++Target Architecture+ (or its _variant_), or done in the +Toolchain+ menu.
>
> I think this text is misleading, because it suggests that the only way
> to avoid rebuilding the toolchain over and over again is to build a
> toolchain with Buildroot, and then use it as an external toolchain in
> Buildroot. There are other options that are possible:
>  * Use Crosstool-NG outside of Buildroot to generate a toolchain
>  * Use a pre-built toolchain
Here, I only focus on the internal backend, but I agree it may not be
as clear as I thought...

>
> I have the feeling that this new text doesn't articulate very well with
> the text that was added in 401d323698266468e322471530ee1997835fc335.
My bad :s, I forgot to check how it goes with the rest of the manual...

>
> We have to be careful to not add a set of random facts in the manual
> one after the other, without keeping a consistency and ordering on the
> different parts of the manual.
Agree.

Well, I see 2 options (at least) to rework this patch:
- either reword it (still as a faq entry) to properly integrate it
with the rest of the manual;
- or add this workaround in the paragraph "Internal toolchain backend"
from the section 3.1.1.

But any other suggestion is welcome.


Regards,