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Subject[PATCH 2/2] UIO: Documentation for UIO ioport info handling
This patch updates UIO documentation with the changes introduced by
PATCH 1/2.

Signed-off-by: Hans J. Koch <hjk@linutronix.de>

---
Documentation/DocBook/uio-howto.tmpl | 97 +++++++++++++++++++++++++++++++++++
1 file changed, 97 insertions(+)

Index: linux-2.6.28-rc/Documentation/DocBook/uio-howto.tmpl
===================================================================
--- linux-2.6.28-rc.orig/Documentation/DocBook/uio-howto.tmpl 2008-12-06 01:13:56.000000000 +0100
+++ linux-2.6.28-rc/Documentation/DocBook/uio-howto.tmpl 2008-12-06 01:54:14.000000000 +0100
@@ -42,6 +42,12 @@

<revhistory>
<revision>
+ <revnumber>0.6</revnumber>
+ <date>2008-12-05</date>
+ <authorinitials>hjk</authorinitials>
+ <revremark>Added description of portio sysfs attributes.</revremark>
+ </revision>
+ <revision>
<revnumber>0.5</revnumber>
<date>2008-05-22</date>
<authorinitials>hjk</authorinitials>
@@ -318,6 +324,54 @@
offset = N * getpagesize();
</programlisting>

+<para>
+ Sometimes there is hardware with memory-like regions that can not be
+ mapped with the technique described here, but there are still ways to
+ access them from userspace. The most common example are x86 ioports.
+ On x86 systems, userspace can access these ioports using
+ <function>ioperm()</function>, <function>iopl()</function>,
+ <function>inb()</function>, <function>outb()</function>, and similar
+ functions.
+</para>
+<para>
+ Since these ioport regions can not be mapped, they will not appear under
+ <filename>/sys/class/uio/uioX/maps/</filename> like the normal memory
+ described above. Without information about the port regions a hardware
+ has to offer, it becomes difficult for the userspace part of the
+ driver to find out which ports belong to which UIO device.
+</para>
+<para>
+ To address this situation, the new directory
+ <filename>/sys/class/uio/uioX/portio/</filename> was added. It only
+ exists if the driver wants to pass information about one or more port
+ regions to userspace. If that is the case, subdirectories named
+ <filename>port0</filename>, <filename>port1</filename>, and so on,
+ will appear underneath
+ <filename>/sys/class/uio/uioX/portio/</filename>.
+</para>
+<para>
+ Each <filename>portX/</filename> directory contains three read-only
+ files that show start, size, and type of the port region:
+</para>
+<itemizedlist>
+<listitem>
+ <para>
+ <filename>start</filename>: The first port of this region.
+ </para>
+</listitem>
+<listitem>
+ <para>
+ <filename>size</filename>: The number of ports in this region.
+ </para>
+</listitem>
+<listitem>
+ <para>
+ <filename>porttype</filename>: A string describing the type of port.
+ </para>
+</listitem>
+</itemizedlist>
+
+
</sect1>
</chapter>

@@ -356,6 +410,13 @@
</para></listitem>

<listitem><para>
+<varname>struct uio_port port[ MAX_UIO_PORTS_REGIONS ]</varname>: Required
+if you want to pass information about ioports to userspace. For each port
+region you need to fill one of the <varname>uio_port</varname> structures.
+See the description below for details.
+</para></listitem>
+
+<listitem><para>
<varname>long irq</varname>: Required. If your hardware generates an
interrupt, it's your modules task to determine the irq number during
initialization. If you don't have a hardware generated interrupt but
@@ -448,6 +509,42 @@
<varname>struct uio_mem</varname>! It is used by the UIO framework
to set up sysfs files for this mapping. Simply leave it alone.
</para>
+
+<para>
+Sometimes, your device can have one or more port regions which can not be
+mapped to userspace. But if there are other possibilities for userspace to
+access these ports, it makes sense to make information about the ports
+available in sysfs. For each region, you have to set up a
+<varname>struct uio_port</varname> in the <varname>port[]</varname> array.
+Here's a description of the fields of <varname>struct uio_port</varname>:
+</para>
+
+<itemizedlist>
+<listitem><para>
+<varname>char *porttype</varname>: Required. Set this to one of the predefined
+constants. Use <varname>UIO_PORT_X86</varname> for the ioports found in x86
+architectures.
+</para></listitem>
+
+<listitem><para>
+<varname>unsigned long start</varname>: Required if the port region is used.
+Fill in the number of the first port of this region.
+</para></listitem>
+
+<listitem><para>
+<varname>unsigned long size</varname>: Fill in the number of ports in this
+region. If <varname>size</varname> is zero, the region is considered unused.
+Note that you <emphasis>must</emphasis> initialize <varname>size</varname>
+with zero for all unused regions.
+</para></listitem>
+</itemizedlist>
+
+<para>
+Please do not touch the <varname>portio</varname> element of
+<varname>struct uio_port</varname>! It is used internally by the UIO
+framework to set up sysfs files for this region. Simply leave it alone.
+</para>
+
</sect1>

<sect1 id="adding_irq_handler">

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