UIO: Documentation for UIO ioport info handling
This patch updates UIO documentation with the changes introduced by previous UIO patch. Signed-off-by: Hans J. Koch <hjk@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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@ -41,6 +41,12 @@ GPL version 2.
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</abstract>
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<revhistory>
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<revision>
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<revnumber>0.6</revnumber>
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<date>2008-12-05</date>
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<authorinitials>hjk</authorinitials>
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<revremark>Added description of portio sysfs attributes.</revremark>
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</revision>
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<revision>
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<revnumber>0.5</revnumber>
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<date>2008-05-22</date>
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@ -318,6 +324,54 @@ interested in translating it, please email me
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offset = N * getpagesize();
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</programlisting>
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<para>
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Sometimes there is hardware with memory-like regions that can not be
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mapped with the technique described here, but there are still ways to
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access them from userspace. The most common example are x86 ioports.
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On x86 systems, userspace can access these ioports using
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<function>ioperm()</function>, <function>iopl()</function>,
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<function>inb()</function>, <function>outb()</function>, and similar
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functions.
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</para>
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<para>
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Since these ioport regions can not be mapped, they will not appear under
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<filename>/sys/class/uio/uioX/maps/</filename> like the normal memory
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described above. Without information about the port regions a hardware
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has to offer, it becomes difficult for the userspace part of the
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driver to find out which ports belong to which UIO device.
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</para>
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<para>
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To address this situation, the new directory
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<filename>/sys/class/uio/uioX/portio/</filename> was added. It only
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exists if the driver wants to pass information about one or more port
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regions to userspace. If that is the case, subdirectories named
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<filename>port0</filename>, <filename>port1</filename>, and so on,
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will appear underneath
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<filename>/sys/class/uio/uioX/portio/</filename>.
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</para>
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<para>
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Each <filename>portX/</filename> directory contains three read-only
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files that show start, size, and type of the port region:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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<filename>start</filename>: The first port of this region.
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</para>
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</listitem>
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<listitem>
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<para>
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<filename>size</filename>: The number of ports in this region.
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</para>
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</listitem>
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<listitem>
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<para>
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<filename>porttype</filename>: A string describing the type of port.
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</para>
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</listitem>
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</itemizedlist>
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</sect1>
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</chapter>
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@ -355,6 +409,13 @@ mapping you need to fill one of the <varname>uio_mem</varname> structures.
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See the description below for details.
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</para></listitem>
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<listitem><para>
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<varname>struct uio_port port[ MAX_UIO_PORTS_REGIONS ]</varname>: Required
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if you want to pass information about ioports to userspace. For each port
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region you need to fill one of the <varname>uio_port</varname> structures.
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See the description below for details.
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</para></listitem>
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<listitem><para>
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<varname>long irq</varname>: Required. If your hardware generates an
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interrupt, it's your modules task to determine the irq number during
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@ -448,6 +509,42 @@ Please do not touch the <varname>kobj</varname> element of
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<varname>struct uio_mem</varname>! It is used by the UIO framework
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to set up sysfs files for this mapping. Simply leave it alone.
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</para>
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<para>
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Sometimes, your device can have one or more port regions which can not be
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mapped to userspace. But if there are other possibilities for userspace to
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access these ports, it makes sense to make information about the ports
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available in sysfs. For each region, you have to set up a
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<varname>struct uio_port</varname> in the <varname>port[]</varname> array.
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Here's a description of the fields of <varname>struct uio_port</varname>:
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</para>
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<itemizedlist>
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<listitem><para>
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<varname>char *porttype</varname>: Required. Set this to one of the predefined
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constants. Use <varname>UIO_PORT_X86</varname> for the ioports found in x86
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architectures.
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</para></listitem>
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<listitem><para>
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<varname>unsigned long start</varname>: Required if the port region is used.
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Fill in the number of the first port of this region.
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</para></listitem>
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<listitem><para>
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<varname>unsigned long size</varname>: Fill in the number of ports in this
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region. If <varname>size</varname> is zero, the region is considered unused.
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Note that you <emphasis>must</emphasis> initialize <varname>size</varname>
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with zero for all unused regions.
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</para></listitem>
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</itemizedlist>
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<para>
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Please do not touch the <varname>portio</varname> element of
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<varname>struct uio_port</varname>! It is used internally by the UIO
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framework to set up sysfs files for this region. Simply leave it alone.
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</para>
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</sect1>
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<sect1 id="adding_irq_handler">
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