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Add uio_dmem_genirq description to UIO documentation

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Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>
Signed-off-by: "Hans J. Koch" <hjk@hansjkoch.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Damian Hobson-Garcia 2012-09-25 15:09:12 +09:00 committed by Greg Kroah-Hartman
parent 0a0c3b5a24
commit b533a83008
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Documentation/DocBook/uio-howto.tmpl
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@ -719,6 +719,62 @@ framework to set up sysfs files for this region. Simply leave it alone.
</para>
</sect1>
<sect1 id="using uio_dmem_genirq">
<title>Using uio_dmem_genirq for platform devices</title>
<para>
In addition to statically allocated memory ranges, they may also be
a desire to use dynamically allocated regions in a user space driver.
In particular, being able to access memory made available through the
dma-mapping API, may be particularly useful. The
<varname>uio_dmem_genirq</varname> driver provides a way to accomplish
this.
</para>
<para>
This driver is used in a similar manner to the
<varname>"uio_pdrv_genirq"</varname> driver with respect to interrupt
configuration and handling.
</para>
<para>
Set the <varname>.name</varname> element of
<varname>struct platform_device</varname> to
<varname>"uio_dmem_genirq"</varname> to use this driver.
</para>
<para>
When using this driver, fill in the <varname>.platform_data</varname>
element of <varname>struct platform_device</varname>, which is of type
<varname>struct uio_dmem_genirq_pdata</varname> and which contains the
following elements:
</para>
<itemizedlist>
<listitem><varname>struct uio_info uioinfo</varname>: The same
structure used as the <varname>uio_pdrv_genirq</varname> platform
data</listitem>
<listitem><varname>unsigned int *dynamic_region_sizes</varname>:
Pointer to list of sizes of dynamic memory regions to be mapped into
user space.
</listitem>
<listitem><varname>unsigned int num_dynamic_regions</varname>:
Number of elements in <varname>dynamic_region_sizes</varname> array.
</listitem>
</itemizedlist>
<para>
The dynamic regions defined in the platform data will be appended to
the <varname> mem[] </varname> array after the platform device
resources, which implies that the total number of static and dynamic
memory regions cannot exceed <varname>MAX_UIO_MAPS</varname>.
</para>
<para>
The dynamic memory regions will be allocated when the UIO device file,
<varname>/dev/uioX</varname> is opened.
Simiar to static memory resources, the memory region information for
dynamic regions is then visible via sysfs at
<varname>/sys/class/uio/uioX/maps/mapY/*</varname>.
The dynmaic memory regions will be freed when the UIO device file is
closed. When no processes are holding the device file open, the address
returned to userspace is DMA_ERROR_CODE.
</para>
</sect1>
</chapter>
<chapter id="userspace_driver" xreflabel="Writing a driver in user space">