[bootlin/training-materials updates] master: common: printk: add example of print configuration (4b0f1d40)

[Clément Léger]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/4b0f1d4047da3d6bdf5a9e8e41a5aa2fe70cef44

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

commit 4b0f1d4047da3d6bdf5a9e8e41a5aa2fe70cef44
Author: Clément Léger <clement.leger at bootlin.com>
Date:   Fri Nov 25 11:09:58 2022 +0100

    common: printk: add example of print configuration
    
    Signed-off-by: Clément Léger <clement.leger at bootlin.com>


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

4b0f1d4047da3d6bdf5a9e8e41a5aa2fe70cef44
 common/printk.tex | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/common/printk.tex b/common/printk.tex
index c79a6faa..93ecf969 100644
--- a/common/printk.tex
+++ b/common/printk.tex
@@ -96,9 +96,30 @@ dev_info(&pdev->dev, "in probe\n");
   \end{itemize}
 \end{frame}
 
-
 \ifthenelse{\equal{\training}{debugging}}{
-  }{}
+\begin{frame}
+  \frametitle{pr\_debug() and dev\_dbg() usage}
+  \begin{itemize}
+  \item Debug prints can be enabled using the
+    \code{/sys/kernel/debug/dynamic_debug/control} file.
+  \begin{itemize}
+    \item \code{cat /sys/kernel/debug/dynamic_debug/control} will display all
+      lines that can be enabled in the kernel
+    \item Example: \code{init/main.c:1427 [main]run_init_process =p "    \%s\012"}
+  \end{itemize}
+  \item A syntax allows to enable individual print using lines, files or modules
+  \begin{itemize}
+    \item \code{echo "file drivers/pinctrl/core.c +p" > /sys/kernel/debug/dynamic_debug/control}
+      will enable all debug prints in \code{drivers/pinctrl/core.c}
+    \item \code{echo "module pciehp +p" > /sys/kernel/debug/dynamic_debug/control}
+      will enable the debug print located in the \code{pciehp} module
+    \item \code{echo "line init/main.c:1427 +p" > /sys/kernel/debug/dynamic_debug/control}
+      will enable the debug print located at line 1247 of file \code{init/main.c}
+    \item Replace \code{+p} with \code{-p} to disable the debug print
+  \end{itemize}
+  \end{itemize}
+\end{frame}
+}{}
 
 \ifthenelse{\equal{\training}{linux-kernel}}{
 \begin{frame}