[FE training-materials-updates] buildroot-advanced-packages: Config.in.legacy

[Thomas Petazzoni]

Repository : git://git.free-electrons.com/training-materials.git

On branch  : master
Link       : http://git.free-electrons.com/training-materials/commit/?id=f7ac7df988258b4b41eb0e49b3ae80641a072562

>---------------------------------------------------------------

commit f7ac7df988258b4b41eb0e49b3ae80641a072562
Author: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Date:   Tue May 5 16:40:22 2015 +0200

    buildroot-advanced-packages: Config.in.legacy
    
    Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>


>---------------------------------------------------------------

f7ac7df988258b4b41eb0e49b3ae80641a072562
 .../buildroot-advanced-packages.tex                        | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/slides/buildroot-advanced-packages/buildroot-advanced-packages.tex b/slides/buildroot-advanced-packages/buildroot-advanced-packages.tex
index 7611e16..d7dfaa4 100644
--- a/slides/buildroot-advanced-packages/buildroot-advanced-packages.tex
+++ b/slides/buildroot-advanced-packages/buildroot-advanced-packages.tex
@@ -444,6 +444,20 @@ $(eval $(autotools-package))
 
 \end{frame}
 
+\begin{frame}{Legacy handling: {\tt Config.in.legacy}}
+  \begin{itemize}
+  \item When a \code{Config.in} option is removed, the corresponding
+    value in the \code{.config} is silently removed.
+  \item Due to this, when users upgrade Buildroot, they generally
+    don't know that an option they were using has been removed.
+  \item To prevent this, Buildroot keeps in \code{Config.in.legacy}
+    handling all the removed options, and when one of them is enabled
+    refuses to build.
+  \item When options that have been part of a Buildroot release are
+    removed, they are moved to this file.
+  \end{itemize}
+\end{frame}
+
 \setuplabframe
 {Advanced packages}
 {