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| -rw-r--r-- | Documentation/DocBook/uio-howto.tmpl | 90 |
1 files changed, 32 insertions, 58 deletions
diff --git a/Documentation/DocBook/uio-howto.tmpl b/Documentation/DocBook/uio-howto.tmpl index c119484258b..fdd7f4f887b 100644 --- a/Documentation/DocBook/uio-howto.tmpl +++ b/Documentation/DocBook/uio-howto.tmpl @@ -30,6 +30,12 @@ <revhistory> <revision> + <revnumber>0.4</revnumber> + <date>2007-11-26</date> + <authorinitials>hjk</authorinitials> + <revremark>Removed section about uio_dummy.</revremark> + </revision> + <revision> <revnumber>0.3</revnumber> <date>2007-04-29</date> <authorinitials>hjk</authorinitials> @@ -94,6 +100,26 @@ interested in translating it, please email me user space. This simplifies development and reduces the risk of serious bugs within a kernel module. </para> + <para> + Please note that UIO is not an universal driver interface. Devices + that are already handled well by other kernel subsystems (like + networking or serial or USB) are no candidates for an UIO driver. + Hardware that is ideally suited for an UIO driver fulfills all of + the following: + </para> +<itemizedlist> +<listitem> + <para>The device has memory that can be mapped. The device can be + controlled completely by writing to this memory.</para> +</listitem> +<listitem> + <para>The device usually generates interrupts.</para> +</listitem> +<listitem> + <para>The device does not fit into one of the standard kernel + subsystems.</para> +</listitem> +</itemizedlist> </sect1> <sect1 id="thanks"> @@ -174,8 +200,9 @@ interested in translating it, please email me For cards that don't generate interrupts but need to be polled, there is the possibility to set up a timer that triggers the interrupt handler at configurable time intervals. - See <filename>drivers/uio/uio_dummy.c</filename> for an - example of this technique. + This interrupt simulation is done by calling + <function>uio_event_notify()</function> + from the timer's event handler. </para> <para> @@ -263,63 +290,11 @@ offset = N * getpagesize(); </sect1> </chapter> -<chapter id="using-uio_dummy" xreflabel="Using uio_dummy"> -<?dbhtml filename="using-uio_dummy.html"?> -<title>Using uio_dummy</title> - <para> - Well, there is no real use for uio_dummy. Its only purpose is - to test most parts of the UIO system (everything except - hardware interrupts), and to serve as an example for the - kernel module that you will have to write yourself. - </para> - -<sect1 id="what_uio_dummy_does"> -<title>What uio_dummy does</title> - <para> - The kernel module <filename>uio_dummy.ko</filename> creates a - device that uses a timer to generate periodic interrupts. The - interrupt handler does nothing but increment a counter. The - driver adds two custom attributes, <varname>count</varname> - and <varname>freq</varname>, that appear under - <filename>/sys/devices/platform/uio_dummy/</filename>. - </para> - - <para> - The attribute <varname>count</varname> can be read and - written. The associated file - <filename>/sys/devices/platform/uio_dummy/count</filename> - appears as a normal text file and contains the total number of - timer interrupts. If you look at it (e.g. using - <function>cat</function>), you'll notice it is slowly counting - up. - </para> - - <para> - The attribute <varname>freq</varname> can be read and written. - The content of - <filename>/sys/devices/platform/uio_dummy/freq</filename> - represents the number of system timer ticks between two timer - interrupts. The default value of <varname>freq</varname> is - the value of the kernel variable <varname>HZ</varname>, which - gives you an interval of one second. Lower values will - increase the frequency. Try the following: - </para> -<programlisting format="linespecific"> -cd /sys/devices/platform/uio_dummy/ -echo 100 > freq -</programlisting> - <para> - Use <function>cat count</function> to see how the interrupt - frequency changes. - </para> -</sect1> -</chapter> - <chapter id="custom_kernel_module" xreflabel="Writing your own kernel module"> <?dbhtml filename="custom_kernel_module.html"?> <title>Writing your own kernel module</title> <para> - Please have a look at <filename>uio_dummy.c</filename> as an + Please have a look at <filename>uio_cif.c</filename> as an example. The following paragraphs explain the different sections of this file. </para> @@ -354,9 +329,8 @@ See the description below for details. interrupt, it's your modules task to determine the irq number during initialization. If you don't have a hardware generated interrupt but want to trigger the interrupt handler in some other way, set -<varname>irq</varname> to <varname>UIO_IRQ_CUSTOM</varname>. The -uio_dummy module does this as it triggers the event mechanism in a timer -routine. If you had no interrupt at all, you could set +<varname>irq</varname> to <varname>UIO_IRQ_CUSTOM</varname>. +If you had no interrupt at all, you could set <varname>irq</varname> to <varname>UIO_IRQ_NONE</varname>, though this rarely makes sense. </para></listitem> |