[bootlin/training-materials updates] master: sysdev-linux: sources: Enhance the slide (6b73dac1)

[Miquel Raynal]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/6b73dac11ad32d57e03185dd9c493cfd9ad35d4b

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

commit 6b73dac11ad32d57e03185dd9c493cfd9ad35d4b
Author: Miquel Raynal <miquel.raynal at bootlin.com>
Date:   Tue May 31 10:47:01 2022 +0200

    sysdev-linux: sources: Enhance the slide
    
    Make a real distinction between mainline and stable.
    
    Move secondary kernels (vendors/sub-community trees) in another slide to
    lighten a bit.
    
    Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>


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

6b73dac11ad32d57e03185dd9c493cfd9ad35d4b
 .../sysdev-linux-intro-sources.tex                 | 50 ++++++++++++++++------
 1 file changed, 36 insertions(+), 14 deletions(-)

diff --git a/slides/sysdev-linux-intro-sources/sysdev-linux-intro-sources.tex b/slides/sysdev-linux-intro-sources/sysdev-linux-intro-sources.tex
index cea38161..65dd1b99 100644
--- a/slides/sysdev-linux-intro-sources/sysdev-linux-intro-sources.tex
+++ b/slides/sysdev-linux-intro-sources/sysdev-linux-intro-sources.tex
@@ -1,32 +1,54 @@
 \subsection{Linux kernel sources}
 
 \begin{frame}
-  \frametitle{Location of kernel sources}
+  \frametitle{Location of official kernel sources}
   \begin{itemize}
-  \item The official ({\em mainline}) versions of the Linux kernel, as released by Linus
+  \item The mainline versions of the Linux kernel, as released by Linus
     Torvalds, are available at \url{https://kernel.org}
     \begin{itemize}
     \item These versions follow the development model of the kernel
-    \item However, they may not contain the latest developments from a
-      specific area yet. Some features in development might not be
-      ready for mainline inclusion yet.
+    \item They may not contain the latest developments from a specific
+      area yet
+    \item A good pick for products development phase
     \end{itemize}
+    \item The stable versions of the Linux kernel, as maintained by a
+      maintainers group, are also available at \url{https://kernel.org}
+    \begin{itemize}
+    \item These versions do not bring new features compared to Linus'
+      tree
+    \item Only bug fixes and security fixes are pulled there
+    \item Each version is stabilized during the development period of
+      the next mainline kernel
+    \item Certain versions can be maintained for much longer, 2$+$ years
+    \item A good pick for products commercialization phase
+    \end{itemize}
+  \end{itemize}
+\end{frame}
+
+\begin{frame}
+  \frametitle{Location of non-official kernel sources}
+  \begin{itemize}
   \item Many chip vendors supply their own kernel sources
     \begin{itemize}
     \item Focusing on hardware support first
     \item Can have a very important delta with mainline Linux
-    \item Useful only when mainline hasn't caught up yet. Many vendors
-          invest in the mainline kernel at the same time.
+    \item Sometimes they break support for other platforms/devices
+      without caring
+    \item Useful in early phases only when mainline hasn't caught up yet
+      (many vendors invest in the mainline kernel at the same time)
+    \item Suitable for PoC, not suitable for products on the long term
+      as usually no updates are provided to these kernels
+    \item Getting stuck with a deprecated system with broken software
+      that cannot be udpated has a real cost in the end
     \end{itemize}
   \item Many kernel sub-communities maintain their own kernel, with
-    usually newer but fewer stable features
+    usually newer but fewer stable features, only for cutting-edge
+    development
     \begin{itemize}
-    \item Architecture communities (ARM, MIPS, PowerPC, etc.), device
-      drivers communities (I2C, SPI, USB, PCI, network, etc.), other
-      communities (real-time, etc.)
-    \item No official releases, only meant for sharing work and
-      contributing to the mainline version. Absolutely not meant
-      to be used in products.
+    \item Architecture communities (ARM, MIPS, PowerPC, etc)
+    \item Device drivers communities (I2C, SPI, USB, PCI, network, etc)
+    \item Other communities (real-time, etc)
+    \item Not suitable to be used in products
     \end{itemize}
   \end{itemize}
 \end{frame}