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authorLinus Torvalds <torvalds@linux-foundation.org>2017-02-23 03:51:29 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-23 03:51:29 +0100
commitc1aac62f36c1e37ee81c9e09ee9ee733eef05dcb (patch)
treeb400b92c44faf7da37d37138145e895a55eaa4cc /Documentation/DocBook
parentMerge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm (diff)
parentdocs / driver-api: Fix structure references in device_link.rst (diff)
downloadlinux-c1aac62f36c1e37ee81c9e09ee9ee733eef05dcb.tar.xz
linux-c1aac62f36c1e37ee81c9e09ee9ee733eef05dcb.zip
Merge tag 'docs-4.11' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet: "A slightly quieter cycle for documentation this time around. Three more DocBook template files have been converted to RST; only 21 to go. There are various build improvements and the usual array of documentation improvements and fixes" * tag 'docs-4.11' of git://git.lwn.net/linux: (44 commits) docs / driver-api: Fix structure references in device_link.rst PM / docs: Fix structure references in device.rst Add a target to check broken external links in the Documentation Documentation: Fix linux-api list typo Documentation: DocBook/Makefile comment typo Improve sparse documentation Documentation: make Makefile.sphinx no-ops quieter Documentation: DMA-ISA-LPC.txt Documentation: input: fix path to input code definitions docs: Remove the copyright year from conf.py docs: Fix a warning in the Korean HOWTO.rst translation PM / sleep / docs: Convert PM notifiers document to reST PM / core / docs: Convert sleep states API document to reST PM / core: Update kerneldoc comments in pm.h doc-rst: Fix recursive make invocation from macros doc-rst: Delete output of failed dot-SVG conversion doc-rst: Break shell command sequences on failure Documentation/sphinx: make targets independent of Sphinx work for HAVE_SPHINX=0 doc-rst: fixed cleandoc target when used with O=dir Documentation/sphinx: prevent generation of .pyc files in the source tree ...
Diffstat (limited to 'Documentation/DocBook')
-rw-r--r--Documentation/DocBook/Makefile5
-rw-r--r--Documentation/DocBook/deviceiobook.tmpl323
-rw-r--r--Documentation/DocBook/iio.tmpl697
-rw-r--r--Documentation/DocBook/regulator.tmpl304
4 files changed, 3 insertions, 1326 deletions
diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile
index 5fd8f5effd0c..60a17b7da834 100644
--- a/Documentation/DocBook/Makefile
+++ b/Documentation/DocBook/Makefile
@@ -13,7 +13,7 @@ DOCBOOKS := z8530book.xml \
gadget.xml libata.xml mtdnand.xml librs.xml rapidio.xml \
genericirq.xml s390-drivers.xml scsi.xml \
sh.xml regulator.xml w1.xml \
- writing_musb_glue_layer.xml iio.xml
+ writing_musb_glue_layer.xml
ifeq ($(DOCBOOKS),)
@@ -71,6 +71,7 @@ installmandocs: mandocs
# no-op for the DocBook toolchain
epubdocs:
latexdocs:
+linkcheckdocs:
###
#External programs used
@@ -272,6 +273,6 @@ cleandocs:
$(Q)rm -rf $(call objectify, $(clean-dirs))
# Declare the contents of the .PHONY variable as phony. We keep that
-# information in a variable se we can use it in if_changed and friends.
+# information in a variable so we can use it in if_changed and friends.
.PHONY: $(PHONY)
diff --git a/Documentation/DocBook/deviceiobook.tmpl b/Documentation/DocBook/deviceiobook.tmpl
deleted file mode 100644
index 54199a0dcf9a..000000000000
--- a/Documentation/DocBook/deviceiobook.tmpl
+++ /dev/null
@@ -1,323 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-
-<book id="DoingIO">
- <bookinfo>
- <title>Bus-Independent Device Accesses</title>
-
- <authorgroup>
- <author>
- <firstname>Matthew</firstname>
- <surname>Wilcox</surname>
- <affiliation>
- <address>
- <email>matthew@wil.cx</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <authorgroup>
- <author>
- <firstname>Alan</firstname>
- <surname>Cox</surname>
- <affiliation>
- <address>
- <email>alan@lxorguk.ukuu.org.uk</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2001</year>
- <holder>Matthew Wilcox</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 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.
- </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>
-
- <chapter id="intro">
- <title>Introduction</title>
- <para>
- Linux provides an API which abstracts performing IO across all busses
- and devices, allowing device drivers to be written independently of
- bus type.
- </para>
- </chapter>
-
- <chapter id="bugs">
- <title>Known Bugs And Assumptions</title>
- <para>
- None.
- </para>
- </chapter>
-
- <chapter id="mmio">
- <title>Memory Mapped IO</title>
- <sect1 id="getting_access_to_the_device">
- <title>Getting Access to the Device</title>
- <para>
- The most widely supported form of IO is memory mapped IO.
- That is, a part of the CPU's address space is interpreted
- not as accesses to memory, but as accesses to a device. Some
- architectures define devices to be at a fixed address, but most
- have some method of discovering devices. The PCI bus walk is a
- good example of such a scheme. This document does not cover how
- to receive such an address, but assumes you are starting with one.
- Physical addresses are of type unsigned long.
- </para>
-
- <para>
- This address should not be used directly. Instead, to get an
- address suitable for passing to the accessor functions described
- below, you should call <function>ioremap</function>.
- An address suitable for accessing the device will be returned to you.
- </para>
-
- <para>
- After you've finished using the device (say, in your module's
- exit routine), call <function>iounmap</function> in order to return
- the address space to the kernel. Most architectures allocate new
- address space each time you call <function>ioremap</function>, and
- they can run out unless you call <function>iounmap</function>.
- </para>
- </sect1>
-
- <sect1 id="accessing_the_device">
- <title>Accessing the device</title>
- <para>
- The part of the interface most used by drivers is reading and
- writing memory-mapped registers on the device. Linux provides
- interfaces to read and write 8-bit, 16-bit, 32-bit and 64-bit
- quantities. Due to a historical accident, these are named byte,
- word, long and quad accesses. Both read and write accesses are
- supported; there is no prefetch support at this time.
- </para>
-
- <para>
- The functions are named <function>readb</function>,
- <function>readw</function>, <function>readl</function>,
- <function>readq</function>, <function>readb_relaxed</function>,
- <function>readw_relaxed</function>, <function>readl_relaxed</function>,
- <function>readq_relaxed</function>, <function>writeb</function>,
- <function>writew</function>, <function>writel</function> and
- <function>writeq</function>.
- </para>
-
- <para>
- Some devices (such as framebuffers) would like to use larger
- transfers than 8 bytes at a time. For these devices, the
- <function>memcpy_toio</function>, <function>memcpy_fromio</function>
- and <function>memset_io</function> functions are provided.
- Do not use memset or memcpy on IO addresses; they
- are not guaranteed to copy data in order.
- </para>
-
- <para>
- The read and write functions are defined to be ordered. That is the
- compiler is not permitted to reorder the I/O sequence. When the
- ordering can be compiler optimised, you can use <function>
- __readb</function> and friends to indicate the relaxed ordering. Use
- this with care.
- </para>
-
- <para>
- While the basic functions are defined to be synchronous with respect
- to each other and ordered with respect to each other the busses the
- devices sit on may themselves have asynchronicity. In particular many
- authors are burned by the fact that PCI bus writes are posted
- asynchronously. A driver author must issue a read from the same
- device to ensure that writes have occurred in the specific cases the
- author cares. This kind of property cannot be hidden from driver
- writers in the API. In some cases, the read used to flush the device
- may be expected to fail (if the card is resetting, for example). In
- that case, the read should be done from config space, which is
- guaranteed to soft-fail if the card doesn't respond.
- </para>
-
- <para>
- The following is an example of flushing a write to a device when
- the driver would like to ensure the write's effects are visible prior
- to continuing execution.
- </para>
-
-<programlisting>
-static inline void
-qla1280_disable_intrs(struct scsi_qla_host *ha)
-{
- struct device_reg *reg;
-
- reg = ha->iobase;
- /* disable risc and host interrupts */
- WRT_REG_WORD(&amp;reg->ictrl, 0);
- /*
- * The following read will ensure that the above write
- * has been received by the device before we return from this
- * function.
- */
- RD_REG_WORD(&amp;reg->ictrl);
- ha->flags.ints_enabled = 0;
-}
-</programlisting>
-
- <para>
- In addition to write posting, on some large multiprocessing systems
- (e.g. SGI Challenge, Origin and Altix machines) posted writes won't
- be strongly ordered coming from different CPUs. Thus it's important
- to properly protect parts of your driver that do memory-mapped writes
- with locks and use the <function>mmiowb</function> to make sure they
- arrive in the order intended. Issuing a regular <function>readX
- </function> will also ensure write ordering, but should only be used
- when the driver has to be sure that the write has actually arrived
- at the device (not that it's simply ordered with respect to other
- writes), since a full <function>readX</function> is a relatively
- expensive operation.
- </para>
-
- <para>
- Generally, one should use <function>mmiowb</function> prior to
- releasing a spinlock that protects regions using <function>writeb
- </function> or similar functions that aren't surrounded by <function>
- readb</function> calls, which will ensure ordering and flushing. The
- following pseudocode illustrates what might occur if write ordering
- isn't guaranteed via <function>mmiowb</function> or one of the
- <function>readX</function> functions.
- </para>
-
-<programlisting>
-CPU A: spin_lock_irqsave(&amp;dev_lock, flags)
-CPU A: ...
-CPU A: writel(newval, ring_ptr);
-CPU A: spin_unlock_irqrestore(&amp;dev_lock, flags)
- ...
-CPU B: spin_lock_irqsave(&amp;dev_lock, flags)
-CPU B: writel(newval2, ring_ptr);
-CPU B: ...
-CPU B: spin_unlock_irqrestore(&amp;dev_lock, flags)
-</programlisting>
-
- <para>
- In the case above, newval2 could be written to ring_ptr before
- newval. Fixing it is easy though:
- </para>
-
-<programlisting>
-CPU A: spin_lock_irqsave(&amp;dev_lock, flags)
-CPU A: ...
-CPU A: writel(newval, ring_ptr);
-CPU A: mmiowb(); /* ensure no other writes beat us to the device */
-CPU A: spin_unlock_irqrestore(&amp;dev_lock, flags)
- ...
-CPU B: spin_lock_irqsave(&amp;dev_lock, flags)
-CPU B: writel(newval2, ring_ptr);
-CPU B: ...
-CPU B: mmiowb();
-CPU B: spin_unlock_irqrestore(&amp;dev_lock, flags)
-</programlisting>
-
- <para>
- See tg3.c for a real world example of how to use <function>mmiowb
- </function>
- </para>
-
- <para>
- PCI ordering rules also guarantee that PIO read responses arrive
- after any outstanding DMA writes from that bus, since for some devices
- the result of a <function>readb</function> call may signal to the
- driver that a DMA transaction is complete. In many cases, however,
- the driver may want to indicate that the next
- <function>readb</function> call has no relation to any previous DMA
- writes performed by the device. The driver can use
- <function>readb_relaxed</function> for these cases, although only
- some platforms will honor the relaxed semantics. Using the relaxed
- read functions will provide significant performance benefits on
- platforms that support it. The qla2xxx driver provides examples
- of how to use <function>readX_relaxed</function>. In many cases,
- a majority of the driver's <function>readX</function> calls can
- safely be converted to <function>readX_relaxed</function> calls, since
- only a few will indicate or depend on DMA completion.
- </para>
- </sect1>
-
- </chapter>
-
- <chapter id="port_space_accesses">
- <title>Port Space Accesses</title>
- <sect1 id="port_space_explained">
- <title>Port Space Explained</title>
-
- <para>
- Another form of IO commonly supported is Port Space. This is a
- range of addresses separate to the normal memory address space.
- Access to these addresses is generally not as fast as accesses
- to the memory mapped addresses, and it also has a potentially
- smaller address space.
- </para>
-
- <para>
- Unlike memory mapped IO, no preparation is required
- to access port space.
- </para>
-
- </sect1>
- <sect1 id="accessing_port_space">
- <title>Accessing Port Space</title>
- <para>
- Accesses to this space are provided through a set of functions
- which allow 8-bit, 16-bit and 32-bit accesses; also
- known as byte, word and long. These functions are
- <function>inb</function>, <function>inw</function>,
- <function>inl</function>, <function>outb</function>,
- <function>outw</function> and <function>outl</function>.
- </para>
-
- <para>
- Some variants are provided for these functions. Some devices
- require that accesses to their ports are slowed down. This
- functionality is provided by appending a <function>_p</function>
- to the end of the function. There are also equivalents to memcpy.
- The <function>ins</function> and <function>outs</function>
- functions copy bytes, words or longs to the given port.
- </para>
- </sect1>
-
- </chapter>
-
- <chapter id="pubfunctions">
- <title>Public Functions Provided</title>
-!Iarch/x86/include/asm/io.h
-!Elib/pci_iomap.c
- </chapter>
-
-</book>
diff --git a/Documentation/DocBook/iio.tmpl b/Documentation/DocBook/iio.tmpl
deleted file mode 100644
index e2ab6a1f223e..000000000000
--- a/Documentation/DocBook/iio.tmpl
+++ /dev/null
@@ -1,697 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-
-<book id="iioid">
- <bookinfo>
- <title>Industrial I/O driver developer's guide </title>
-
- <authorgroup>
- <author>
- <firstname>Daniel</firstname>
- <surname>Baluta</surname>
- <affiliation>
- <address>
- <email>daniel.baluta@intel.com</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2015</year>
- <holder>Intel Corporation</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 version 2.
- </para>
- </legalnotice>
- </bookinfo>
-
- <toc></toc>
-
- <chapter id="intro">
- <title>Introduction</title>
- <para>
- The main purpose of the Industrial I/O subsystem (IIO) is to provide
- support for devices that in some sense perform either analog-to-digital
- conversion (ADC) or digital-to-analog conversion (DAC) or both. The aim
- is to fill the gap between the somewhat similar hwmon and input
- subsystems.
- Hwmon is directed at low sample rate sensors used to monitor and
- control the system itself, like fan speed control or temperature
- measurement. Input is, as its name suggests, focused on human interaction
- input devices (keyboard, mouse, touchscreen). In some cases there is
- considerable overlap between these and IIO.
- </para>
- <para>
- Devices that fall into this category include:
- <itemizedlist>
- <listitem>
- analog to digital converters (ADCs)
- </listitem>
- <listitem>
- accelerometers
- </listitem>
- <listitem>
- capacitance to digital converters (CDCs)
- </listitem>
- <listitem>
- digital to analog converters (DACs)
- </listitem>
- <listitem>
- gyroscopes
- </listitem>
- <listitem>
- inertial measurement units (IMUs)
- </listitem>
- <listitem>
- color and light sensors
- </listitem>
- <listitem>
- magnetometers
- </listitem>
- <listitem>
- pressure sensors
- </listitem>
- <listitem>
- proximity sensors
- </listitem>
- <listitem>
- temperature sensors
- </listitem>
- </itemizedlist>
- Usually these sensors are connected via SPI or I2C. A common use case of the
- sensors devices is to have combined functionality (e.g. light plus proximity
- sensor).
- </para>
- </chapter>
- <chapter id='iiosubsys'>
- <title>Industrial I/O core</title>
- <para>
- The Industrial I/O core offers:
- <itemizedlist>
- <listitem>
- a unified framework for writing drivers for many different types of
- embedded sensors.
- </listitem>
- <listitem>
- a standard interface to user space applications manipulating sensors.
- </listitem>
- </itemizedlist>
- The implementation can be found under <filename>
- drivers/iio/industrialio-*</filename>
- </para>
- <sect1 id="iiodevice">
- <title> Industrial I/O devices </title>
-
-!Finclude/linux/iio/iio.h iio_dev
-!Fdrivers/iio/industrialio-core.c iio_device_alloc
-!Fdrivers/iio/industrialio-core.c iio_device_free
-!Fdrivers/iio/industrialio-core.c iio_device_register
-!Fdrivers/iio/industrialio-core.c iio_device_unregister
-
- <para>
- An IIO device usually corresponds to a single hardware sensor and it
- provides all the information needed by a driver handling a device.
- Let's first have a look at the functionality embedded in an IIO
- device then we will show how a device driver makes use of an IIO
- device.
- </para>
- <para>
- There are two ways for a user space application to interact
- with an IIO driver.
- <itemizedlist>
- <listitem>
- <filename>/sys/bus/iio/iio:deviceX/</filename>, this
- represents a hardware sensor and groups together the data
- channels of the same chip.
- </listitem>
- <listitem>
- <filename>/dev/iio:deviceX</filename>, character device node
- interface used for buffered data transfer and for events information
- retrieval.
- </listitem>
- </itemizedlist>
- </para>
- A typical IIO driver will register itself as an I2C or SPI driver and will
- create two routines, <function> probe </function> and <function> remove
- </function>. At <function>probe</function>:
- <itemizedlist>
- <listitem>call <function>iio_device_alloc</function>, which allocates memory
- for an IIO device.
- </listitem>
- <listitem> initialize IIO device fields with driver specific information
- (e.g. device name, device channels).
- </listitem>
- <listitem>call <function> iio_device_register</function>, this registers the
- device with the IIO core. After this call the device is ready to accept
- requests from user space applications.
- </listitem>
- </itemizedlist>
- At <function>remove</function>, we free the resources allocated in
- <function>probe</function> in reverse order:
- <itemizedlist>
- <listitem><function>iio_device_unregister</function>, unregister the device
- from the IIO core.
- </listitem>
- <listitem><function>iio_device_free</function>, free the memory allocated
- for the IIO device.
- </listitem>
- </itemizedlist>
-
- <sect2 id="iioattr"> <title> IIO device sysfs interface </title>
- <para>
- Attributes are sysfs files used to expose chip info and also allowing
- applications to set various configuration parameters. For device
- with index X, attributes can be found under
- <filename>/sys/bus/iio/iio:deviceX/ </filename> directory.
- Common attributes are:
- <itemizedlist>
- <listitem><filename>name</filename>, description of the physical
- chip.
- </listitem>
- <listitem><filename>dev</filename>, shows the major:minor pair
- associated with <filename>/dev/iio:deviceX</filename> node.
- </listitem>
- <listitem><filename>sampling_frequency_available</filename>,
- available discrete set of sampling frequency values for
- device.
- </listitem>
- </itemizedlist>
- Available standard attributes for IIO devices are described in the
- <filename>Documentation/ABI/testing/sysfs-bus-iio </filename> file
- in the Linux kernel sources.
- </para>
- </sect2>
- <sect2 id="iiochannel"> <title> IIO device channels </title>
-!Finclude/linux/iio/iio.h iio_chan_spec structure.
- <para>
- An IIO device channel is a representation of a data channel. An
- IIO device can have one or multiple channels. For example:
- <itemizedlist>
- <listitem>
- a thermometer sensor has one channel representing the
- temperature measurement.
- </listitem>
- <listitem>
- a light sensor with two channels indicating the measurements in
- the visible and infrared spectrum.
- </listitem>
- <listitem>
- an accelerometer can have up to 3 channels representing
- acceleration on X, Y and Z axes.
- </listitem>
- </itemizedlist>
- An IIO channel is described by the <type> struct iio_chan_spec
- </type>. A thermometer driver for the temperature sensor in the
- example above would have to describe its channel as follows:
- <programlisting>
- static const struct iio_chan_spec temp_channel[] = {
- {
- .type = IIO_TEMP,
- .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
- },
- };
-
- </programlisting>
- Channel sysfs attributes exposed to userspace are specified in
- the form of <emphasis>bitmasks</emphasis>. Depending on their
- shared info, attributes can be set in one of the following masks:
- <itemizedlist>
- <listitem><emphasis>info_mask_separate</emphasis>, attributes will
- be specific to this channel</listitem>
- <listitem><emphasis>info_mask_shared_by_type</emphasis>,
- attributes are shared by all channels of the same type</listitem>
- <listitem><emphasis>info_mask_shared_by_dir</emphasis>, attributes
- are shared by all channels of the same direction </listitem>
- <listitem><emphasis>info_mask_shared_by_all</emphasis>,
- attributes are shared by all channels</listitem>
- </itemizedlist>
- When there are multiple data channels per channel type we have two
- ways to distinguish between them:
- <itemizedlist>
- <listitem> set <emphasis> .modified</emphasis> field of <type>
- iio_chan_spec</type> to 1. Modifiers are specified using
- <emphasis>.channel2</emphasis> field of the same
- <type>iio_chan_spec</type> structure and are used to indicate a
- physically unique characteristic of the channel such as its direction
- or spectral response. For example, a light sensor can have two channels,
- one for infrared light and one for both infrared and visible light.
- </listitem>
- <listitem> set <emphasis>.indexed </emphasis> field of
- <type>iio_chan_spec</type> to 1. In this case the channel is
- simply another instance with an index specified by the
- <emphasis>.channel</emphasis> field.
- </listitem>
- </itemizedlist>
- Here is how we can make use of the channel's modifiers:
- <programlisting>
- static const struct iio_chan_spec light_channels[] = {
- {
- .type = IIO_INTENSITY,
- .modified = 1,
- .channel2 = IIO_MOD_LIGHT_IR,
- .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
- .info_mask_shared = BIT(IIO_CHAN_INFO_SAMP_FREQ),
- },
- {
- .type = IIO_INTENSITY,
- .modified = 1,
- .channel2 = IIO_MOD_LIGHT_BOTH,
- .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
- .info_mask_shared = BIT(IIO_CHAN_INFO_SAMP_FREQ),
- },
- {
- .type = IIO_LIGHT,
- .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
- .info_mask_shared = BIT(IIO_CHAN_INFO_SAMP_FREQ),
- },
-
- }
- </programlisting>
- This channel's definition will generate two separate sysfs files
- for raw data retrieval:
- <itemizedlist>
- <listitem>
- <filename>/sys/bus/iio/iio:deviceX/in_intensity_ir_raw</filename>
- </listitem>
- <listitem>
- <filename>/sys/bus/iio/iio:deviceX/in_intensity_both_raw</filename>
- </listitem>
- </itemizedlist>
- one file for processed data:
- <itemizedlist>
- <listitem>
- <filename>/sys/bus/iio/iio:deviceX/in_illuminance_input
- </filename>
- </listitem>
- </itemizedlist>
- and one shared sysfs file for sampling frequency:
- <itemizedlist>
- <listitem>
- <filename>/sys/bus/iio/iio:deviceX/sampling_frequency.
- </filename>
- </listitem>
- </itemizedlist>
- </para>
- <para>
- Here is how we can make use of the channel's indexing:
- <programlisting>
- static const struct iio_chan_spec light_channels[] = {
- {
- .type = IIO_VOLTAGE,
- .indexed = 1,
- .channel = 0,
- .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
- },
- {
- .type = IIO_VOLTAGE,
- .indexed = 1,
- .channel = 1,
- .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
- },
- }
- </programlisting>
- This will generate two separate attributes files for raw data
- retrieval:
- <itemizedlist>
- <listitem>
- <filename>/sys/bus/iio/devices/iio:deviceX/in_voltage0_raw</filename>,
- representing voltage measurement for channel 0.
- </listitem>
- <listitem>
- <filename>/sys/bus/iio/devices/iio:deviceX/in_voltage1_raw</filename>,
- representing voltage measurement for channel 1.
- </listitem>
- </itemizedlist>
- </para>
- </sect2>
- </sect1>
-
- <sect1 id="iiobuffer"> <title> Industrial I/O buffers </title>
-!Finclude/linux/iio/buffer.h iio_buffer
-!Edrivers/iio/industrialio-buffer.c
-
- <para>
- The Industrial I/O core offers a way for continuous data capture
- based on a trigger source. Multiple data channels can be read at once
- from <filename>/dev/iio:deviceX</filename> character device node,
- thus reducing the CPU load.
- </para>
-
- <sect2 id="iiobuffersysfs">
- <title>IIO buffer sysfs interface </title>
- <para>
- An IIO buffer has an associated attributes directory under <filename>
- /sys/bus/iio/iio:deviceX/buffer/</filename>. Here are the existing
- attributes:
- <itemizedlist>
- <listitem>
- <emphasis>length</emphasis>, the total number of data samples
- (capacity) that can be stored by the buffer.
- </listitem>
- <listitem>
- <emphasis>enable</emphasis>, activate buffer capture.
- </listitem>
- </itemizedlist>
-
- </para>
- </sect2>
- <sect2 id="iiobuffersetup"> <title> IIO buffer setup </title>
- <para>The meta information associated with a channel reading
- placed in a buffer is called a <emphasis> scan element </emphasis>.
- The important bits configuring scan elements are exposed to
- userspace applications via the <filename>
- /sys/bus/iio/iio:deviceX/scan_elements/</filename> directory. This
- file contains attributes of the following form:
- <itemizedlist>
- <listitem><emphasis>enable</emphasis>, used for enabling a channel.
- If and only if its attribute is non zero, then a triggered capture
- will contain data samples for this channel.
- </listitem>
- <listitem><emphasis>type</emphasis>, description of the scan element
- data storage within the buffer and hence the form in which it is
- read from user space. Format is <emphasis>
- [be|le]:[s|u]bits/storagebitsXrepeat[>>shift] </emphasis>.
- <itemizedlist>
- <listitem> <emphasis>be</emphasis> or <emphasis>le</emphasis>, specifies
- big or little endian.
- </listitem>
- <listitem>
- <emphasis>s </emphasis>or <emphasis>u</emphasis>, specifies if
- signed (2's complement) or unsigned.
- </listitem>
- <listitem><emphasis>bits</emphasis>, is the number of valid data
- bits.
- </listitem>
- <listitem><emphasis>storagebits</emphasis>, is the number of bits
- (after padding) that it occupies in the buffer.
- </listitem>
- <listitem>
- <emphasis>shift</emphasis>, if specified, is the shift that needs
- to be applied prior to masking out unused bits.
- </listitem>
- <listitem>
- <emphasis>repeat</emphasis>, specifies the number of bits/storagebits
- repetitions. When the repeat element is 0 or 1, then the repeat
- value is omitted.
- </listitem>
- </itemizedlist>
- </listitem>
- </itemizedlist>
- For example, a driver for a 3-axis accelerometer with 12 bit
- resolution where data is stored in two 8-bits registers as
- follows:
- <programlisting>
- 7 6 5 4 3 2 1 0
- +---+---+---+---+---+---+---+---+
- |D3 |D2 |D1 |D0 | X | X | X | X | (LOW byte, address 0x06)
- +---+---+---+---+---+---+---+---+
-
- 7 6 5 4 3 2 1 0
- +---+---+---+---+---+---+---+---+
- |D11|D10|D9 |D8 |D7 |D6 |D5 |D4 | (HIGH byte, address 0x07)
- +---+---+---+---+---+---+---+---+
- </programlisting>
-
- will have the following scan element type for each axis:
- <programlisting>
- $ cat /sys/bus/iio/devices/iio:device0/scan_elements/in_accel_y_type
- le:s12/16>>4
- </programlisting>
- A user space application will interpret data samples read from the
- buffer as two byte little endian signed data, that needs a 4 bits
- right shift before masking out the 12 valid bits of data.
- </para>
- <para>
- For implementing buffer support a driver should initialize the following
- fields in <type>iio_chan_spec</type> definition:
- <programlisting>
- struct iio_chan_spec {
- /* other members */
- int scan_index
- struct {
- char sign;
- u8 realbits;
- u8 storagebits;
- u8 shift;
- u8 repeat;
- enum iio_endian endianness;
- } scan_type;
- };
- </programlisting>
- The driver implementing the accelerometer described above will
- have the following channel definition:
- <programlisting>
- struct struct iio_chan_spec accel_channels[] = {
- {
- .type = IIO_ACCEL,
- .modified = 1,
- .channel2 = IIO_MOD_X,
- /* other stuff here */
- .scan_index = 0,
- .scan_type = {
- .sign = 's',
- .realbits = 12,
- .storagebits = 16,
- .shift = 4,
- .endianness = IIO_LE,
- },
- }
- /* similar for Y (with channel2 = IIO_MOD_Y, scan_index = 1)
- * and Z (with channel2 = IIO_MOD_Z, scan_index = 2) axis
- */
- }
- </programlisting>
- </para>
- <para>
- Here <emphasis> scan_index </emphasis> defines the order in which
- the enabled channels are placed inside the buffer. Channels with a lower
- scan_index will be placed before channels with a higher index. Each
- channel needs to have a unique scan_index.
- </para>
- <para>
- Setting scan_index to -1 can be used to indicate that the specific
- channel does not support buffered capture. In this case no entries will
- be created for the channel in the scan_elements directory.
- </para>
- </sect2>
- </sect1>
-
- <sect1 id="iiotrigger"> <title> Industrial I/O triggers </title>
-!Finclude/linux/iio/trigger.h iio_trigger
-!Edrivers/iio/industrialio-trigger.c
- <para>
- In many situations it is useful for a driver to be able to
- capture data based on some external event (trigger) as opposed
- to periodically polling for data. An IIO trigger can be provided
- by a device driver that also has an IIO device based on hardware
- generated events (e.g. data ready or threshold exceeded) or
- provided by a separate driver from an independent interrupt
- source (e.g. GPIO line connected to some external system, timer
- interrupt or user space writing a specific file in sysfs). A
- trigger may initiate data capture for a number of sensors and
- also it may be completely unrelated to the sensor itself.
- </para>
-
- <sect2 id="iiotrigsysfs"> <title> IIO trigger sysfs interface </title>
- There are two locations in sysfs related to triggers:
- <itemizedlist>
- <listitem><filename>/sys/bus/iio/devices/triggerY</filename>,
- this file is created once an IIO trigger is registered with
- the IIO core and corresponds to trigger with index Y. Because
- triggers can be very different depending on type there are few
- standard attributes that we can describe here:
- <itemizedlist>
- <listitem>
- <emphasis>name</emphasis>, trigger name that can be later
- used for association with a device.
- </listitem>
- <listitem>
- <emphasis>sampling_frequency</emphasis>, some timer based
- triggers use this attribute to specify the frequency for
- trigger calls.
- </listitem>
- </itemizedlist>
- </listitem>
- <listitem>
- <filename>/sys/bus/iio/devices/iio:deviceX/trigger/</filename>, this
- directory is created once the device supports a triggered
- buffer. We can associate a trigger with our device by writing
- the trigger's name in the <filename>current_trigger</filename> file.
- </listitem>
- </itemizedlist>
- </sect2>
-
- <sect2 id="iiotrigattr"> <title> IIO trigger setup</title>
-
- <para>
- Let's see a simple example of how to setup a trigger to be used
- by a driver.
-
- <programlisting>
- struct iio_trigger_ops trigger_ops = {
- .set_trigger_state = sample_trigger_state,
- .validate_device = sample_validate_device,
- }
-
- struct iio_trigger *trig;
-
- /* first, allocate memory for our trigger */
- trig = iio_trigger_alloc(dev, "trig-%s-%d", name, idx);
-
- /* setup trigger operations field */
- trig->ops = &amp;trigger_ops;
-
- /* now register the trigger with the IIO core */
- iio_trigger_register(trig);
- </programlisting>
- </para>
- </sect2>
-
- <sect2 id="iiotrigsetup"> <title> IIO trigger ops</title>
-!Finclude/linux/iio/trigger.h iio_trigger_ops
- <para>
- Notice that a trigger has a set of operations attached:
- <itemizedlist>
- <listitem>
- <function>set_trigger_state</function>, switch the trigger on/off
- on demand.
- </listitem>
- <listitem>
- <function>validate_device</function>, function to validate the
- device when the current trigger gets changed.
- </listitem>
- </itemizedlist>
- </para>
- </sect2>
- </sect1>
- <sect1 id="iiotriggered_buffer">
- <title> Industrial I/O triggered buffers </title>
- <para>
- Now that we know what buffers and triggers are let's see how they
- work together.
- </para>
- <sect2 id="iiotrigbufsetup"> <title> IIO triggered buffer setup</title>
-!Edrivers/iio/buffer/industrialio-triggered-buffer.c
-!Finclude/linux/iio/iio.h iio_buffer_setup_ops
-
-
- <para>
- A typical triggered buffer setup looks like this:
- <programlisting>
- const struct iio_buffer_setup_ops sensor_buffer_setup_ops = {
- .preenable = sensor_buffer_preenable,
- .postenable = sensor_buffer_postenable,
- .postdisable = sensor_buffer_postdisable,
- .predisable = sensor_buffer_predisable,
- };
-
- irqreturn_t sensor_iio_pollfunc(int irq, void *p)
- {
- pf->timestamp = iio_get_time_ns((struct indio_dev *)p);
- return IRQ_WAKE_THREAD;
- }
-
- irqreturn_t sensor_trigger_handler(int irq, void *p)
- {
- u16 buf[8];
- int i = 0;
-
- /* read data for each active channel */
- for_each_set_bit(bit, active_scan_mask, masklength)
- buf[i++] = sensor_get_data(bit)
-
- iio_push_to_buffers_with_timestamp(indio_dev, buf, timestamp);
-
- iio_trigger_notify_done(trigger);
- return IRQ_HANDLED;
- }
-
- /* setup triggered buffer, usually in probe function */
- iio_triggered_buffer_setup(indio_dev, sensor_iio_polfunc,
- sensor_trigger_handler,
- sensor_buffer_setup_ops);
- </programlisting>
- </para>
- The important things to notice here are:
- <itemizedlist>
- <listitem><function> iio_buffer_setup_ops</function>, the buffer setup
- functions to be called at predefined points in the buffer configuration
- sequence (e.g. before enable, after disable). If not specified, the
- IIO core uses the default <type>iio_triggered_buffer_setup_ops</type>.
- </listitem>
- <listitem><function>sensor_iio_pollfunc</function>, the function that
- will be used as top half of poll function. It should do as little
- processing as possible, because it runs in interrupt context. The most
- common operation is recording of the current timestamp and for this reason
- one can use the IIO core defined <function>iio_pollfunc_store_time
- </function> function.
- </listitem>
- <listitem><function>sensor_trigger_handler</function>, the function that
- will be used as bottom half of the poll function. This runs in the
- context of a kernel thread and all the processing takes place here.
- It usually reads data from the device and stores it in the internal
- buffer together with the timestamp recorded in the top half.
- </listitem>
- </itemizedlist>
- </sect2>
- </sect1>
- </chapter>
- <chapter id='iioresources'>
- <title> Resources </title>
- IIO core may change during time so the best documentation to read is the
- source code. There are several locations where you should look:
- <itemizedlist>
- <listitem>
- <filename>drivers/iio/</filename>, contains the IIO core plus
- and directories for each sensor type (e.g. accel, magnetometer,
- etc.)
- </listitem>
- <listitem>
- <filename>include/linux/iio/</filename>, contains the header
- files, nice to read for the internal kernel interfaces.
- </listitem>
- <listitem>
- <filename>include/uapi/linux/iio/</filename>, contains files to be
- used by user space applications.
- </listitem>
- <listitem>
- <filename>tools/iio/</filename>, contains tools for rapidly
- testing buffers, events and device creation.
- </listitem>
- <listitem>
- <filename>drivers/staging/iio/</filename>, contains code for some
- drivers or experimental features that are not yet mature enough
- to be moved out.
- </listitem>
- </itemizedlist>
- <para>
- Besides the code, there are some good online documentation sources:
- <itemizedlist>
- <listitem>
- <ulink url="http://marc.info/?l=linux-iio"> Industrial I/O mailing
- list </ulink>
- </listitem>
- <listitem>
- <ulink url="http://wiki.analog.com/software/linux/docs/iio/iio">
- Analog Device IIO wiki page </ulink>
- </listitem>
- <listitem>
- <ulink url="https://fosdem.org/2015/schedule/event/iiosdr/">
- Using the Linux IIO framework for SDR, Lars-Peter Clausen's
- presentation at FOSDEM </ulink>
- </listitem>
- </itemizedlist>
- </para>
- </chapter>
-</book>
-
-<!--
-vim: softtabstop=2:shiftwidth=2:expandtab:textwidth=72
--->
diff --git a/Documentation/DocBook/regulator.tmpl b/Documentation/DocBook/regulator.tmpl
deleted file mode 100644
index 3b08a085d2c7..000000000000
--- a/Documentation/DocBook/regulator.tmpl
+++ /dev/null
@@ -1,304 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-
-<book id="regulator-api">
- <bookinfo>
- <title>Voltage and current regulator API</title>
-
- <authorgroup>
- <author>
- <firstname>Liam</firstname>
- <surname>Girdwood</surname>
- <affiliation>
- <address>
- <email>lrg@slimlogic.co.uk</email>
- </address>
- </affiliation>
- </author>
- <author>
- <firstname>Mark</firstname>
- <surname>Brown</surname>
- <affiliation>
- <orgname>Wolfson Microelectronics</orgname>
- <address>
- <email>broonie@opensource.wolfsonmicro.com</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2007-2008</year>
- <holder>Wolfson Microelectronics</holder>
- </copyright>
- <copyright>
- <year>2008</year>
- <holder>Liam Girdwood</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 version 2 as published by the Free Software Foundation.
- </para>
-
- <para>
- 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.
- </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>
-
- <chapter id="intro">
- <title>Introduction</title>
- <para>
- This framework is designed to provide a standard kernel
- interface to control voltage and current regulators.
- </para>
- <para>
- The intention is to allow systems to dynamically control
- regulator power output in order to save power and prolong
- battery life. This applies to both voltage regulators (where
- voltage output is controllable) and current sinks (where current
- limit is controllable).
- </para>
- <para>
- Note that additional (and currently more complete) documentation
- is available in the Linux kernel source under
- <filename>Documentation/power/regulator</filename>.
- </para>
-
- <sect1 id="glossary">
- <title>Glossary</title>
- <para>
- The regulator API uses a number of terms which may not be
- familiar:
- </para>
- <glossary>
-
- <glossentry>
- <glossterm>Regulator</glossterm>
- <glossdef>
- <para>
- Electronic device that supplies power to other devices. Most
- regulators can enable and disable their output and some can also
- control their output voltage or current.
- </para>
- </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm>Consumer</glossterm>
- <glossdef>
- <para>
- Electronic device which consumes power provided by a regulator.
- These may either be static, requiring only a fixed supply, or
- dynamic, requiring active management of the regulator at
- runtime.
- </para>
- </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm>Power Domain</glossterm>
- <glossdef>
- <para>
- The electronic circuit supplied by a given regulator, including
- the regulator and all consumer devices. The configuration of
- the regulator is shared between all the components in the
- circuit.
- </para>
- </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm>Power Management Integrated Circuit</glossterm>
- <acronym>PMIC</acronym>
- <glossdef>
- <para>
- An IC which contains numerous regulators and often also other
- subsystems. In an embedded system the primary PMIC is often
- equivalent to a combination of the PSU and southbridge in a
- desktop system.
- </para>
- </glossdef>
- </glossentry>
- </glossary>
- </sect1>
- </chapter>
-
- <chapter id="consumer">
- <title>Consumer driver interface</title>
- <para>
- This offers a similar API to the kernel clock framework.
- Consumer drivers use <link
- linkend='API-regulator-get'>get</link> and <link
- linkend='API-regulator-put'>put</link> operations to acquire and
- release regulators. Functions are
- provided to <link linkend='API-regulator-enable'>enable</link>
- and <link linkend='API-regulator-disable'>disable</link> the
- regulator and to get and set the runtime parameters of the
- regulator.
- </para>
- <para>
- When requesting regulators consumers use symbolic names for their
- supplies, such as "Vcc", which are mapped into actual regulator
- devices by the machine interface.
- </para>
- <para>
- A stub version of this API is provided when the regulator
- framework is not in use in order to minimise the need to use
- ifdefs.
- </para>
-
- <sect1 id="consumer-enable">
- <title>Enabling and disabling</title>
- <para>
- The regulator API provides reference counted enabling and
- disabling of regulators. Consumer devices use the <function><link
- linkend='API-regulator-enable'>regulator_enable</link></function>
- and <function><link
- linkend='API-regulator-disable'>regulator_disable</link>
- </function> functions to enable and disable regulators. Calls
- to the two functions must be balanced.
- </para>
- <para>
- Note that since multiple consumers may be using a regulator and
- machine constraints may not allow the regulator to be disabled
- there is no guarantee that calling
- <function>regulator_disable</function> will actually cause the
- supply provided by the regulator to be disabled. Consumer
- drivers should assume that the regulator may be enabled at all
- times.
- </para>
- </sect1>
-
- <sect1 id="consumer-config">
- <title>Configuration</title>
- <para>
- Some consumer devices may need to be able to dynamically
- configure their supplies. For example, MMC drivers may need to
- select the correct operating voltage for their cards. This may
- be done while the regulator is enabled or disabled.
- </para>
- <para>
- The <function><link
- linkend='API-regulator-set-voltage'>regulator_set_voltage</link>
- </function> and <function><link
- linkend='API-regulator-set-current-limit'
- >regulator_set_current_limit</link>
- </function> functions provide the primary interface for this.
- Both take ranges of voltages and currents, supporting drivers
- that do not require a specific value (eg, CPU frequency scaling
- normally permits the CPU to use a wider range of supply
- voltages at lower frequencies but does not require that the
- supply voltage be lowered). Where an exact value is required
- both minimum and maximum values should be identical.
- </para>
- </sect1>
-
- <sect1 id="consumer-callback">
- <title>Callbacks</title>
- <para>
- Callbacks may also be <link
- linkend='API-regulator-register-notifier'>registered</link>
- for events such as regulation failures.
- </para>
- </sect1>
- </chapter>
-
- <chapter id="driver">
- <title>Regulator driver interface</title>
- <para>
- Drivers for regulator chips <link
- linkend='API-regulator-register'>register</link> the regulators
- with the regulator core, providing operations structures to the
- core. A <link
- linkend='API-regulator-notifier-call-chain'>notifier</link> interface
- allows error conditions to be reported to the core.
- </para>
- <para>
- Registration should be triggered by explicit setup done by the
- platform, supplying a <link
- linkend='API-struct-regulator-init-data'>struct
- regulator_init_data</link> for the regulator containing
- <link linkend='machine-constraint'>constraint</link> and
- <link linkend='machine-supply'>supply</link> information.
- </para>
- </chapter>
-
- <chapter id="machine">
- <title>Machine interface</title>
- <para>
- This interface provides a way to define how regulators are
- connected to consumers on a given system and what the valid
- operating parameters are for the system.
- </para>
-
- <sect1 id="machine-supply">
- <title>Supplies</title>
- <para>
- Regulator supplies are specified using <link
- linkend='API-struct-regulator-consumer-supply'>struct
- regulator_consumer_supply</link>. This is done at
- <link linkend='driver'>driver registration
- time</link> as part of the machine constraints.
- </para>
- </sect1>
-
- <sect1 id="machine-constraint">
- <title>Constraints</title>
- <para>
- As well as defining the connections the machine interface
- also provides constraints defining the operations that
- clients are allowed to perform and the parameters that may be
- set. This is required since generally regulator devices will
- offer more flexibility than it is safe to use on a given
- system, for example supporting higher supply voltages than the
- consumers are rated for.
- </para>
- <para>
- This is done at <link linkend='driver'>driver
- registration time</link> by providing a <link
- linkend='API-struct-regulation-constraints'>struct
- regulation_constraints</link>.
- </para>
- <para>
- The constraints may also specify an initial configuration for the
- regulator in the constraints, which is particularly useful for
- use with static consumers.
- </para>
- </sect1>
- </chapter>
-
- <chapter id="api">
- <title>API reference</title>
- <para>
- Due to limitations of the kernel documentation framework and the
- existing layout of the source code the entire regulator API is
- documented here.
- </para>
-!Iinclude/linux/regulator/consumer.h
-!Iinclude/linux/regulator/machine.h
-!Iinclude/linux/regulator/driver.h
-!Edrivers/regulator/core.c
- </chapter>
-</book>