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SubjectRE: [PATCH] Procfs Guide
Date
So where can find the whole docbook ?  I could not find under
linux/Documentation directory.

Regards,
-hiren
(408)970-3062
hiren_mehta@agilent.com

> -----Original Message-----
> From: Erik Mouw [mailto:J.A.K.Mouw@ITS.TUDelft.NL]
> Sent: Wednesday, May 30, 2001 1:36 PM
> To: Tim Waugh
> Cc: Linux kernel mailing list; Alan Cox
> Subject: Re: [PATCH] Procfs Guide
>
>
> On Wed, May 30, 2001 at 09:30:48AM +0100, Tim Waugh wrote:
> > On Wed, May 30, 2001 at 01:29:17AM +0200, Erik Mouw wrote:
> > > I'm still looking for a proper way to automatically
> include the example
> > > source into the SGML file, this patch with the same content in two
> > > files is a bit of an ugly hack.
> >
> > Probably your best bet is to get the Makefile to pass a copy of the
> > real example source through sed to &entity;ify the bits that would
> > confuse SGML (<, >, etc), and into example.c.sed, make that into an
> > entity, and include it.
> >
> > See <URL:http://people.redhat.com/twaugh/docbook/selfdocbook/> for
> > instance, which does this with its own SGML source.
>
> Thanks, that was a really helpful example.
>
> So how about this version?
>
>
> Erik
>
> --
> J.A.K. (Erik) Mouw, Information and Communication Theory
> Group, Department
> of Electrical Engineering, Faculty of Information Technology
> and Systems,
> Delft University of Technology, PO BOX 5031, 2600 GA Delft,
> The Netherlands
> Phone: +31-15-2783635 Fax: +31-15-2781843 Email:
> J.A.K.Mouw@its.tudelft.nl
> WWW: http://www-ict.its.tudelft.nl/~erik/
>
>
> Index: Documentation/DocBook/Makefile
> ===================================================================
> RCS file: /home/erik/cvsroot/elinux/Documentation/DocBook/Makefile,v
> retrieving revision 1.1.1.30
> retrieving revision 1.1.1.25.2.2
> diff -u -r1.1.1.30 -r1.1.1.25.2.2
> --- Documentation/DocBook/Makefile 2001/05/15 12:14:07 1.1.1.30
> +++ Documentation/DocBook/Makefile 2001/05/30 20:31:18
> 1.1.1.25.2.2
> @@ -1,7 +1,7 @@
> BOOKS := wanbook.sgml z8530book.sgml mcabook.sgml
> videobook.sgml \
> kernel-api.sgml parportbook.sgml kernel-hacking.sgml \
> kernel-locking.sgml via-audio.sgml mousedrivers.sgml
> sis900.sgml \
> - deviceiobook.sgml
> + deviceiobook.sgml procfs-guide.sgml
>
> PS := $(patsubst %.sgml, %.ps, $(BOOKS))
> PDF := $(patsubst %.sgml, %.pdf, $(BOOKS))
> @@ -9,6 +9,7 @@
> IMG-parportbook := parport-share.fig parport-multi.fig
> parport-structure.fig
> EPS-parportbook := $(patsubst %.fig, %.eps, $(IMG-parportbook))
> JPG-parportbook := $(patsubst %.fig, %.jpeg, $(IMG-parportbook))
> +C-procfs-example = procfs_example.sgml
>
> books: $(BOOKS)
>
> @@ -67,6 +68,17 @@
> $(TOPDIR)/scripts/docgen
> $(TOPDIR)/drivers/media/video/videodev.c \
> <videobook.tmpl >videobook.sgml
>
> +procfs_example.sgml: procfs_example.c
> + echo "<programlisting>" > $@
> + expand --tabs=8 < $< | \
> + sed -e "s/&/\\&amp;/g" \
> + -e "s/</\\&lt;/g" \
> + -e "s/>/\\&gt;/g" >> $@
> + echo "</programlisting>" >> $@
> +
> +procfs-guide.sgml: procfs-guide.tmpl procfs_example.sgml
> + $(TOPDIR)/scripts/docgen < procfs-guide.tmpl >$@
> +
> APISOURCES := $(TOPDIR)/drivers/media/video/videodev.c \
> $(TOPDIR)/arch/i386/kernel/irq.c \
> $(TOPDIR)/arch/i386/kernel/mca.c \
> @@ -128,6 +140,7 @@
> -$(RM) $(BOOKS)
> -$(RM) $(DVI) $(AUX) $(TEX) $(LOG) $(OUT)
> -$(RM) $(JPG-parportbook) $(EPS-parportbook)
> + -$(RM) $(C-procfs-example)
>
> mrproper: clean
> -$(RM) $(PS) $(PDF)
> Index: Documentation/DocBook/procfs-guide.tmpl
> ===================================================================
> RCS file: procfs-guide.tmpl
> diff -N procfs-guide.tmpl
> --- /dev/null Thu Mar 22 14:04:47 2001
> +++ Documentation/DocBook/procfs-guide.tmpl Wed May 30 22:32:02 2001
> @@ -0,0 +1,603 @@
> +<!-- -*- sgml -*- -->
> +<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V3.1//EN"[
> +<!ENTITY procfsexample SYSTEM "procfs_example.sgml">
> +]>
> +
> +<book id="LKProcfsGuide">
> + <bookinfo>
> + <title>Linux Kernel Procfs Guide</title>
> +
> +
> + <authorgroup>
> + <author>
> + <firstname>Erik</firstname>
> + <othername>(J.A.K.)</othername>
> + <surname>Mouw</surname>
> + <affiliation>
> + <orgname>Delft University of Technology</orgname>
> + <orgdiv>Faculty of Information Technology and Systems</orgdiv>
> + <address>
> + <email>J.A.K.Mouw@its.tudelft.nl</email>
> + <pob>PO BOX 5031</pob>
> + <postcode>2600 GA</postcode>
> + <city>Delft</city>
> + <country>The Netherlands</country>
> + </address>
> + </affiliation>
> + </author>
> + </authorgroup>
> +
> +
> + <copyright>
> + <year>2001</year>
> + <holder>Erik Mouw</holder>
> + </copyright>
> +
> +
> + <legalnotice>
> + <para>
> + This documentation is free software; you can redistribute it
> + and/or modify it under the terms of the GNU General Public
> + License as published by the Free Software Foundation; either
> + version 2 of the License, or (at your option) any later
> + version.
> + </para>
> +
> + <para>
> + This documentation is distributed in the hope that it will be
> + useful, but WITHOUT ANY WARRANTY; without even the implied
> + warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
> + PURPOSE. See the GNU General Public License for
> more details.
> + </para>
> +
> + <para>
> + You should have received a copy of the GNU General Public
> + License along with this program; if not, write to the Free
> + Software Foundation, Inc., 59 Temple Place, Suite
> 330, Boston,
> + MA 02111-1307 USA
> + </para>
> +
> + <para>
> + For more details see the file COPYING in the source
> + distribution of Linux.
> + </para>
> + </legalnotice>
> + </bookinfo>
> +
> +
> +
> +
> + <toc>
> + </toc>
> +
> +
> +
> +
> + <preface>
> + <title>Preface</title>
> +
> + <para>
> + This guide describes the use of the procfs file system from
> + within the Linux kernel. The idea to write this guide
> came up on
> + the #kernelnewbies IRC channel (see <ulink
> +
> url="http://www.kernelnewbies.org/">http://www.kernelnewbies.o
> rg/</ulink>),
> + when Jeff Garzik explained the use of procfs and forwarded me a
> + message Alexander Viro wrote to the linux-kernel
> mailing list. I
> + agreed to write it up nicely, so here it is.
> + </para>
> +
> + <para>
> + I'd like to thank Jeff Garzik
> + <email>jgarzik@mandrakesoft.com</email> and Alexander Viro
> + <email>viro@math.psu.edu</email> for their input, and Tim Waugh
> + <email>twaugh@redhat.com</email> for his <ulink
> +
> url="http://people.redhat.com/twaugh/docbook/selfdocbook/">Sel
> fdocbook</ulink>.
> + </para>
> +
> + <para>
> + This documentation was written while working on the LART
> + computing board (<ulink
> +
> url="http://www.lart.tudelft.nl/">http://www.lart.tudelft.nl/<
> /ulink>).
> + The development has been sponsored by the Mobile Multi-media
> + Communications (<ulink
> +
> url="http://www.mmc.tudelft.nl/">http://www.mmc.tudelft.nl/</ulink>)
> + and Ubiquitous Communications (<ulink
> +
> url="http://www.ubicom.tudelft.nl/">http://www.ubicom.tudelft.
> nl/</ulink>)
> + projects.
> + </para>
> +
> + <para>
> + Erik
> + </para>
> + </preface>
> +
> +
> +
> +
> + <chapter id="intro">
> + <title>Introduction</title>
> +
> + <para>
> + The <filename class="directory">/proc</filename> file system
> + (procfs) is a special file system in the linux kernel. It's a
> + virtual file system: it is not associated with a block
> device but
> + exists only in memory. The files in the procfs are
> used to allow
> + userland programs access to certain information from the kernel
> + (like process information in <filename
> + class="directory">/proc/[0-9]+/</filename>), but also for debug
> + purposes (like <filename>/proc/ksyms</filename>).
> + </para>
> +
> + <para>
> + This guide describes the use of the procfs file system from
> + within the Linux kernel. It starts by introducing all relevant
> + functions to manage the files within the file system.
> After that
> + it shows how to communicate with userland, and some tips and
> + tricks will be pointed out. Finally a complete example will be
> + shown.
> + </para>
> + </chapter>
> +
> +
> +
> +
> + <chapter id="managing">
> + <title>Managing procfs entries</title>
> +
> + <para>
> + This chapter describes the functions that various kernel
> + components use to populate the procfs with files, symlinks,
> + device nodes, and directories.
> + </para>
> +
> + <para>
> + A minor note before we start: if you want to use any of the
> + procfs functions, be sure to include the correct header file!
> + This should be one of the first lines in your code:
> + </para>
> +
> + <programlisting>
> +#include &lt;linux/proc_fs.h&gt;
> + </programlisting>
> +
> +
> +
> +
> + <sect1 id="regularfile">
> + <title>Creating a regular file</title>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>struct proc_dir_entry*
> <function>create_proc_entry</function></funcdef>
> + <paramdef>const char* <parameter>name</parameter></paramdef>
> + <paramdef>mode_t <parameter>mode</parameter></paramdef>
> + <paramdef>struct proc_dir_entry*
> <parameter>parent</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + This function creates a regular file with the name
> + <parameter>name</parameter>, file mode
> + <parameter>mode</parameter> in the directory
> + <parameter>parent</parameter>. To create a file in
> the root of
> + the procfs, use <constant>NULL</constant> as
> + <parameter>parent</parameter> parameter. When successful, the
> + function will return a pointer to the freshly created
> + <structname>struct proc_dir_entry</structname>; otherwise it
> + will return <constant>NULL</constant>. <xref
> + linkend="userland"> describes how to do something useful with
> + regular files.
> + <para>
> +
> + <para>
> + Note that it is specifically supported that you can pass a
> + multi-directory path. For example
> +
> <function>create_proc_entry</function>(<parameter>"drivers/via
0/info"</parameter>)
> + will create the <filename class="directory">via0</filename>
> + directory if necessary, with standard
> + <constant>0755</constant> permissions.
> + </para>
> +
> + <para>
> + If you only want to be able to read the file, the function
> + <function>create_proc_read_entry</function> described in <xref
> + linkend="convenience"> might be used to create and initialise
> + the procfs entry in one single call.
> + </para>
> + </sect1>
> +
> +
> +
> +
> + <sect1>
> + <title>Creating a symlink</title>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>struct proc_dir_entry*
> + <function>proc_symlink</function></funcdef> <paramdef>const
> + char* <parameter>name</parameter></paramdef>
> + <paramdef>struct proc_dir_entry*
> + <parameter>parent</parameter></paramdef> <paramdef>const
> + char* <parameter>dest</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + This creates a symlink in the procfs directory
> + <parameter>parent</parameter> that points from
> + <parameter>name</parameter> to
> + <parameter>dest</parameter>. This translates in userland to
> + <literal>ln -s</literal> <parameter>dest</parameter>
> + <parameter>name</parameter>.
> + </para>
> + </sect1>
> +
> +
> +
> +
> + <sect1>
> + <title>Creating a device</title>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>struct proc_dir_entry*
> <function>proc_mknod</function></funcdef>
> + <paramdef>const char* <parameter>name</parameter></paramdef>
> + <paramdef>mode_t <parameter>mode</parameter></paramdef>
> + <paramdef>struct proc_dir_entry*
> <parameter>parent</parameter></paramdef>
> + <paramdef>kdev_t <parameter>rdev</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + Creates a device file <parameter>name</parameter> with mode
> + <parameter>mode</parameter> in the procfs directory
> + <parameter>parent</parameter>. The device file will work on
> + the device <parameter>rdev</parameter>, which can be
> generated
> + by using the <literal>MKDEV</literal> macro from
> + <literal>linux/kdev_t.h</literal>. The
> + <parameter>mode</parameter> parameter
> + <emphasis>must</emphasis> contain
> <constant>S_IFBLK</constant>
> + or <constant>S_IFCHR</constant> to create a device
> + node. Compare with userland <literal>mknod
> + --mode=</literal><parameter>mode</parameter>
> + <parameter>name</parameter> <parameter>rdev</parameter>.
> + </para>
> + </sect1>
> +
> +
> +
> +
> + <sect1>
> + <title>Creating a directory</title>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>struct proc_dir_entry*
> <function>proc_mkdir</function></funcdef>
> + <paramdef>const char* <parameter>name</parameter></paramdef>
> + <paramdef>struct proc_dir_entry*
> <parameter>parent</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + Create a directory <parameter>name</parameter> in the procfs
> + directory <parameter>parent</parameter>.
> + </para>
> + </sect1>
> +
> +
> +
> +
> + <sect1>
> + <title>Removing an entry</title>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>void <function>remove_proc_entry</function></funcdef>
> + <paramdef>const char* <parameter>name</parameter></paramdef>
> + <paramdef>struct proc_dir_entry*
> <parameter>parent</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + Removes the entry <parameter>name</parameter> in the
> directory
> + <parameter>parent</parameter> from the procfs. Note that
> + entries are removed by their
> <emphasis>name</emphasis>, not by
> + the <structname>struct proc_dir_entry</structname>
> returned by the
> + various create functions.
> + </para>
> +
> + <para>
> + Note that the <structfield>data</structfield> entry from the
> + <structname>struct proc_dir_entry</structname>> has
> to be freed
> + before this function is called (that is: if there was some
> + <structfield>data</structfield> allocated, of course). See
> + <xref linkend="usingdata"> for more information on using the
> + <structfield>data</structfield> entry.
> + </para>
> + </sect1>
> + </chapter>
> +
> +
> +
> +
> + <chapter id="userland">
> + <title>Communicating with userland</title>
> +
> + <para>
> + Instead of reading (or writing) the information directly from
> + kernel memory, the procfs works with <emphasis>call back
> + functions</emphasis> for files: functions that are called when
> + a specific file is being read or written. Those functions have
> + to be initialised after the procfs file is created by setting
> + the <structfield>read_proc</structfield> and/or
> + <structfield>write_proc</structfield> fields in the
> + <structname>struct proc_dir_entry*</structname> the function
> + <function>create_proc_entry</function> returned:
> + </para>
> +
> + <programlisting>
> +struct proc_dir_entry* entry;
> +
> +entry->read_proc = read_proc_foo;
> +entry->write_proc = write_proc_foo;
> + </programlisting>
> +
> + <para>
> + If you only want to use a the
> + <structfield>read_proc</structfield>, the function
> + <function>create_proc_read_entry</function> described in <xref
> + linkend="convenience"> might be used to create and initialise
> + the procfs entry in one single call.
> + </para>
> +
> +
> +
> + <sect1>
> + <title>Reading data</title>
> +
> + <para>
> + The read function is a call back function that
> allows userland
> + processes to read data from the kernel. The read function
> + should have the following format:
> + </para>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>int <function>read_func</function></funcdef>
> + <paramdef>char* <parameter>page</parameter></paramdef>
> + <paramdef>char** <parameter>start</parameter></paramdef>
> + <paramdef>off_t <parameter>off</parameter></paramdef>
> + <paramdef>int <parameter>count</parameter></paramdef>
> + <paramdef>int* <parameter>eof</parameter></paramdef>
> + <paramdef>void* <parameter>data</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + The read function should write its information into the
> + <parameter>page</parameter>. For proper use, the function
> + should start writing at an offset of
> + <parameter>off</parameter> in <parameter>page</parameter> and
> + write <parameter>count</parameter> bytes at maximum, but
> + because most read functions are quite simple and
> only return a
> + small amount of information, these two parameters are usually
> + ignored (it breaks pagers like <literal>more</literal> and
> + <literal>less</literal>, but <literal>cat</literal> still
> + works).
> + </para>
> +
> + <para>
> + If the <parameter>off</parameter> and
> + <parameter>count</parameter> parameters are properly used,
> + <parameter>eof</parameter> should be used to signal that the
> + end of the file has been reached by writing
> + <literal>1</literal> to the memory location
> + <parameter>eof</parameter> points to.
> + </para>
> +
> + <para>
> + The parameter <parameter>start</parameter> doesn't seem to be
> + used anywhere in the kernel. The <parameter>data</parameter>
> + parameter can be used to use a single call back function for
> + several files, see <xref linkend="usingdata">.
> + </para>
> +
> + <para>
> + The <function>read_func</function> function must return the
> + number of bytes written into the <parameter>page</parameter>.
> + </para>
> +
> + <para>
> + <xref linkend="example"> shows how to use a read call back
> + function.
> + </para>
> + </sect1>
> +
> +
> +
> +
> + <sect1>
> + <title>Writing data</title>
> +
> + <para>
> + The write call back function allows a userland
> process to write
> + data to the kernel, so it has some kind of control over the
> + kernel. The write function should have the following format:
> + </para>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>int <function>write_func</function></funcdef>
> + <paramdef>struct file* <parameter>file</parameter></paramdef>
> + <paramdef>const char* <parameter>buffer</parameter></paramdef>
> + <paramdef>unsigned long
> <parameter>count</parameter></paramdef>
> + <paramdef>void* <parameter>data</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + The write function should read <parameter>count</parameter>
> + bytes at maximum from the <parameter>buffer</parameter>. Note
> + that the <parameter>buffer</parameter> doesn't live in the
> + kernel's memory space, so it should first be copied to kernel
> + space with <function>copy_from_user</function>. The
> + <parameter>file</parameter> parameter is usually
> + ignored. <xref linkend="usingdata"> shows how to use the
> + <parameter>data</parameter> parameter.
> + </para>
> +
> + <para>
> + Again, <xref linkend="example"> shows how to use
> this call back
> + function.
> + </para>
> + </sect1>
> +
> +
> +
> +
> + <sect1 id="usingdata">
> + <title>A single call back for many files</title>
> +
> + <para>
> + When a large number of almost identical files is used, it's
> + quite inconvenient to use a separate call back function for
> + each file. Instead of that, a single call back
> function can be
> + used that distinguishes between the files by using
> + <structfield>data</structfield> field in <structname>struct
> + proc_dir_entry</structname>. First of all, the
> + <structfield>data</structfield> field has to be initialised:
> + </para>
> +
> + <programlisting>
> +struct proc_dir_entry* entry;
> +struct my_file_data *file_data;
> +
> +file_data = kmalloc(sizeof(struct my_file_data), GFP_KERNEL);
> +entry->data = file_data;
> + </programlisting>
> +
> + <para>
> + The <structfield>data</structfield> field is a <type>void
> + *</type>, so it can be initialised with anything.
> + </para>
> +
> + <para>
> + Now that the <structfield>data</structfield> field
> is set, the
> + <function>read_proc</function> and
> + <function>write_proc</function> can use it to distinguish
> + between files because they get it passed into their
> + <parameter>data</parameter> parameter:
> + </para>
> +
> + <programlisting>
> +int foo_read_func(char *page, char **start, off_t off,
> + int count, int *eof, void *data)
> +{
> + int len;
> +
> + if(data == file_data) {
> + /* special case for this file */
> + } else {
> + /* normal processing */
> + }
> +
> + return len;
> +}
> + </programlisting>
> +
> + <para>
> + Be sure to free the <structfield>data</structfield>
> data field
> + when removing the procfs entry.
> + </para>
> + </sect1>
> + </chapter>
> +
> +
> +
> +
> + <chapter id="tips">
> + <title>Tips and tricks</title>
> +
> +
> +
> +
> + <sect1 id="convenience">
> + <title>Convenience functions</title>
> +
> + <funcsynopsis>
> + <funcprototype>
> + <funcdef>struct proc_dir_entry*
> <function>create_proc_read_entry</function></funcdef>
> + <paramdef>const char* <parameter>name</parameter></paramdef>
> + <paramdef>mode_t <parameter>mode</parameter></paramdef>
> + <paramdef>struct proc_dir_entry*
> <parameter>parent</parameter></paramdef>
> + <paramdef>read_proc_t*
> <parameter>read_proc</parameter></paramdef>
> + <paramdef>void* <parameter>data</parameter></paramdef>
> + </funcprototype>
> + </funcsynopsis>
> +
> + <para>
> + This function creates a regular file in exactly the same way
> + as <function>create_proc_entry</function> from <xref
> + linkend="regularfile"> does, but also allows to set the read
> + function <parameter>read_proc</parameter> in one call. This
> + function is also able to set the <parameter>data</parameter>,
> + as explained in <xref linkend="usingdata">.
> + </para>
> + </sect1>
> +
> +
> +
> + <sect1>
> + <title>Modules</title>
> +
> + <para>
> + If the procfs is being used from within a module, be sure to
> + set the <structfield>owner</structfield> field in the
> + <structname>struct proc_dir_entry</structname> to
> + <constant>THIS_MODULE</constant>.
> + <para>
> +
> + <programlisting>
> +struct proc_dir_entry* entry;
> +
> +entry->owner = THIS_MODULE;
> + </programlisting>
> + </sect1>
> +
> +
> +
> +
> + <sect1>
> + <title>Mode and ownership</title>
> +
> + <para>
> + Sometimes it is useful to change the mode and/or
> ownership of a
> + procfs entry. Here is an example how to achieve that:
> + </para>
> +
> + <programlisting>
> +struct proc_dir_entry* entry;
> +
> +entry->mode = S_IWUSR |S_IRUSR | S_IRGRP | S_IROTH;
> +entry->uid = 0;
> +entry->gid = 100;
> + </programlisting>
> +
> + </sect1>
> + </chapter>
> +
> +
> +
> +
> + <chapter id="example">
> + <title>Example</title>
> +
> + <!-- be careful with the example code: it shouldn't be wider than
> + approx. 60 columns, or otherwise it won't fit properly on a page
> + -->
> +
> +&procfsexample;
> +
> + </chapter>
> +</book>
> Index: Documentation/DocBook/procfs_example.c
> ===================================================================
> RCS file: procfs_example.c
> diff -N procfs_example.c
> --- /dev/null Thu Mar 22 14:04:47 2001
> +++ Documentation/DocBook/procfs_example.c Wed May 30 22:32:02 2001
> @@ -0,0 +1,247 @@
> +/*
> + * procfs_example.c: an example proc interface
> + *
> + * Copyright (C) 2001, Erik Mouw (J.A.K.Mouw@its.tudelft.nl)
> + *
> + * This file accompanies the procfs-guide in the Linux kernel
> + * source. It's main use is to demonstrate the concepts and
> + * functions described in the guide.
> + *
> + * This software has been developed while working on the LART
> + * computing board (http://www.lart.tudelft.nl/). The
> + * development has been sponsored by the Mobile Multi-media
> + * Communications (http://www.mmc.tudelft.nl/) and Ubiquitous
> + * Communications (http://www.ubicom.tudelft.nl/) projects.
> + *
> + * The author can be reached at:
> + *
> + * Erik Mouw
> + * Information and Communication Theory Group
> + * Faculty of Information Technology and Systems
> + * Delft University of Technology
> + * P.O. Box 5031
> + * 2600 GA Delft
> + * The Netherlands
> + *
> + *
> + * This program is free software; you can redistribute
> + * it and/or modify it under the terms of the GNU General
> + * Public License as published by the Free Software
> + * Foundation; either version 2 of the License, or (at your
> + * option) any later version.
> + *
> + * This program is distributed in the hope that it will be
> + * useful, but WITHOUT ANY WARRANTY; without even the implied
> + * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
> + * PURPOSE. See the GNU General Public License for more
> + * details.
> + *
> + * You should have received a copy of the GNU General Public
> + * License along with this program; if not, write to the
> + * Free Software Foundation, Inc., 59 Temple Place,
> + * Suite 330, Boston, MA 02111-1307 USA
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/proc_fs.h>
> +#include <linux/sched.h>
> +#include <asm/uaccess.h>
> +
> +
> +#define MODULE_VERSION "1.0"
> +#define MODULE_NAME "procfs_example"
> +
> +#define FOOBAR_LEN 8
> +
> +struct fb_data_t {
> + char name[FOOBAR_LEN + 1];
> + char value[FOOBAR_LEN + 1];
> +};
> +
> +
> +static struct proc_dir_entry *example_dir, *foo_file,
> + *bar_file, *jiffies_file, *tty_device, *symlink;
> +
> +
> +struct fb_data_t foo_data, bar_data;
> +
> +
> +static int proc_read_jiffies(char *page, char **start,
> + off_t off, int count,
> + int *eof, void *data)
> +{
> + int len;
> +
> + MOD_INC_USE_COUNT;
> +
> + len = sprintf(page, "jiffies = %ld\n",
> + jiffies);
> +
> + MOD_DEC_USE_COUNT;
> +
> + return len;
> +}
> +
> +
> +static int proc_read_foobar(char *page, char **start,
> + off_t off, int count,
> + int *eof, void *data)
> +{
> + int len;
> + struct fb_data_t *fb_data = (struct fb_data_t *)data;
> +
> + MOD_INC_USE_COUNT;
> +
> + len = sprintf(page, "%s = '%s'\n",
> + fb_data->name, fb_data->value);
> +
> + MOD_DEC_USE_COUNT;
> +
> + return len;
> +}
> +
> +
> +static int proc_write_foobar(struct file *file,
> + const char *buffer,
> + unsigned long count,
> + void *data)
> +{
> + int len;
> + struct fb_data_t *fb_data = (struct fb_data_t *)data;
> +
> + MOD_INC_USE_COUNT;
> +
> + if(count > FOOBAR_LEN)
> + len = FOOBAR_LEN;
> + else
> + len = count;
> +
> + if(copy_from_user(fb_data->value, buffer, len)) {
> + MOD_DEC_USE_COUNT;
> + return -EFAULT;
> + }
> +
> + fb_data->value[len] = '\0';
> +
> + MOD_DEC_USE_COUNT;
> +
> + return len;
> +}
> +
> +
> +static int __init init_procfs_example(void)
> +{
> + int rv = 0;
> +
> + /* create directory */
> + example_dir = proc_mkdir(MODULE_NAME, NULL);
> + if(example_dir == NULL) {
> + rv = -ENOMEM;
> + goto out;
> + }
> +
> + example_dir->owner = THIS_MODULE;
> +
> + /* create jiffies using convenience function */
> + jiffies_file = create_proc_read_entry("jiffies",
> + 0444, example_dir,
> + proc_read_jiffies,
> + NULL);
> + if(jiffies_file == NULL) {
> + rv = -ENOMEM;
> + goto no_jiffies;
> + }
> +
> + jiffies_file->owner = THIS_MODULE;
> +
> + /* create foo and bar files using same callback functions */
> + foo_file = create_proc_entry("foo", 0644, example_dir);
> + if(foo_file == NULL) {
> + rv = -ENOMEM;
> + goto no_foo;
> + }
> +
> + strcpy(foo_data.name, "foo");
> + strcpy(foo_data.value, "foo");
> + foo_file->data = &foo_data;
> + foo_file->read_proc = proc_read_foobar;
> + foo_file->write_proc = proc_write_foobar;
> + foo_file->owner = THIS_MODULE;
> +
> + bar_file = create_proc_entry("bar", 0644, example_dir);
> + if(bar_file == NULL) {
> + rv = -ENOMEM;
> + goto no_bar;
> + }
> +
> + strcpy(bar_data.name, "bar");
> + strcpy(bar_data.value, "bar");
> + bar_file->data = &bar_data;
> + bar_file->read_proc = proc_read_foobar;
> + bar_file->write_proc = proc_write_foobar;
> + bar_file->owner = THIS_MODULE;
> +
> + /* create tty device */
> + tty_device = proc_mknod("tty", S_IFCHR | 0666,
> + example_dir, MKDEV(5, 0));
> + if(tty_device == NULL) {
> + rv = -ENOMEM;
> + goto no_tty;
> + }
> +
> + tty_device->owner = THIS_MODULE;
> +
> + /* create symlink */
> + symlink = proc_symlink("jiffies_too", example_dir,
> + "jiffies");
> + if(symlink == NULL) {
> + rv = -ENOMEM;
> + goto no_symlink;
> + }
> +
> + symlink->owner = THIS_MODULE;
> +
> + /* everything OK */
> + printk(KERN_INFO "%s %s initialised\n",
> + MODULE_NAME, MODULE_VERSION);
> + return 0;
> +
> +no_symlink:
> + remove_proc_entry("tty", example_dir);
> +no_tty:
> + remove_proc_entry("bar", example_dir);
> +no_bar:
> + remove_proc_entry("foo", example_dir);
> +no_foo:
> + remove_proc_entry("jiffies", example_dir);
> +no_jiffies:
> + remove_proc_entry(MODULE_NAME, NULL);
> +out:
> + return rv;
> +}
> +
> +
> +static void __exit cleanup_procfs_example(void)
> +{
> + remove_proc_entry("jiffies_too", example_dir);
> + remove_proc_entry("tty", example_dir);
> + remove_proc_entry("bar", example_dir);
> + remove_proc_entry("foo", example_dir);
> + remove_proc_entry("jiffies", example_dir);
> + remove_proc_entry(MODULE_NAME, NULL);
> +
> + printk(KERN_INFO "%s %s removed\n",
> + MODULE_NAME, MODULE_VERSION);
> +}
> +
> +
> +module_init(init_procfs_example);
> +module_exit(cleanup_procfs_example);
> +
> +MODULE_AUTHOR("Erik Mouw");
> +MODULE_DESCRIPTION("procfs examples");
> +
> +EXPORT_NO_SYMBOLS;
>
>
> -
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