[Buildroot] [PATCHv5 1/5] core: introduce the BR2_EXTERNAL variable

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2013-12-04 19:56 +0100, Thomas Petazzoni spake thusly:
> This commit introduces the BR2_EXTERNAL environment variable, which
> will allow to keep Buildroot customization (board-specific
> configuration files or root filesystem overlays, package Config.in and
> makefiles, as well as defconfigs) outside of the Buildroot tree.
> 
> This commit only introduces the variable itself, and ensures that it
> is available within Config.in options. This allows us to use
> $BR2_EXTERNAL in a 'source' statement in Config.in.
> 
> Following patches extend the usage of BR2_EXTERNAL to other areas
> (packages and defconfigs).
> 
> In details, this commit:
> 
>  * Introduces the BR2_EXTERNAL Kconfig option. This option has no
>    prompt, and is therefore not visible to the user and also not
>    stored in the .config file. It is automatically set to the value of
>    the BR2_EXTERNAL environment variable. The only purpose of this
>    BR2_EXTERNAL Kconfig option is to allow $BR2_EXTERNAL to be
>    properly expanded when used inside Kconfig source statements.
> 
>  * Calculates the BR2_EXTERNAL value to use. If passed on the command
>    line, then this value is taken in priority, and saved to a
>    .br-external hidden file in the output directory. If not passed on
>    the command line, then we read the .br-external file from the
>    output directory. This allows the user to not pass the BR2_EXTERNAL
>    value at each make invocation. If no BR2_EXTERNAL value is passed,
>    we define it to support/dummy-external, so that the kconfig code
>    finds an existing $(BR2_EXTERNAL)/package/Config.in file to
>    include.
> 
>  * Passes the BR2_EXTERNAL into the *config environment, so that its
>    value is found when parsing/evaluating Config.in files and .config
>    values.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Two SoB by Thomas? But I like how they properly line up! ;-)

Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'