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Jim Huang 2023-08-10 15:27:11 +08:00
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lkmpg.tex
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@ -171,7 +171,6 @@ It is reassuring to note that overcoming the initial obstacle in the first attem
If difficulties arise when loading the modules due to versioning errors, consider compiling a kernel with modversioning turned off.
\item Using X Window System.
\label{sec:using_x}
It is highly recommended to extract, compile, and load all the examples discussed in this guide from a console.
Working on these tasks within the X Window System is discouraged.
@ -1710,14 +1709,16 @@ For further details, see:
\label{sec:print_macros}
\subsection{Replacement}
% FIXME: cross-reference
In Section \ref{sec:using_x}, I said that X Window System and kernel module programming do not mix.
That is true for developing kernel modules.
But in actual use, you want to be able to send messages to whichever tty the command to load the module came from.
In Section \ref{sec:preparation}, it was noted that the X Window System and kernel module programming are not conducive to integration.
This remains valid during the development of kernel modules.
However, in practical scenarios, the necessity emerges to relay messages to the tty (teletype) originating the module load command.
"tty" is an abbreviation of \emph{teletype}: originally a combination keyboard-printer used to communicate with a Unix system, and today an abstraction for the text stream used for a Unix program, whether it is a physical terminal, an xterm on an X display, a network connection used with ssh, etc.
The term ``tty'' originates from \emph{teletype}, which initially referred to a combined keyboard-printer for Unix system communication.
Today, it signifies a text stream abstraction employed by Unix programs, encompassing physical terminals,
xterms in X displays, and network connections like SSH.
The way this is done is by using current, a pointer to the currently running task, to get the current task's tty structure.
Then, we look inside that tty structure to find a pointer to a string write function, which we use to write a string to the tty.
To achieve this, the ``current'' pointer is leveraged to access the active task's tty structure.
Within this structure lies a pointer to a string write function, facilitating the string's transmission to the tty.
\samplec{examples/print_string.c}