HOWTO Use the Linux /proc filesystem for debug output
Randy Dunlap <rddunlap AT ieee.org>
2002-April-15


This directory contains three examples of using /proc fs
for presenting debug output from a Linux kernel module.
This is an alternative to using printk().

The first example (procmod.c) uses the traditional
proc_read() and proc_write() interfaces for the
/proc/numbers file.

The second example (procseq.c) uses the seq_file
interface for output (instead of proc_read) but still
uses proc_write() for writing to the /proc/numseq file.

Both examples use proc_write() just to reset the data
values that are printed by the read() methods.

The third example is based on procmod.c and adds a 64-bit
divide/remainder function (divrem64()).  The 64-bit
numbers aren't interesting; it's just an example.

See the source files for more information.

======================================================================

Output from procmod.o via /proc/numbers:

module_name: numbers-debug
version: 0.1
number_current: 1


Output from procseq.o via /proc/numseq:

module_name: numseq-debug
version: 0.1
[0] = 1
[1] = 2
[2] = 3
[3] = 4
[4] = 5
=====

Output from procdiv64.o via /proc/numbers64:

module_name: div64-example
version: 0.1
pages, ctxtsw, t1, t2:  1910057, 122199444, 15, 77065340
pages, jifs, t1, t2:  1910057, 5327393, 358, 2850306
ctxtsw, jifs, t1, t2:  122199444, 5327393, 22937, 5030759

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