diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-22 18:51:29 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-22 18:51:29 -0800 |
commit | c1aac62f36c1e37ee81c9e09ee9ee733eef05dcb (patch) | |
tree | b400b92c44faf7da37d37138145e895a55eaa4cc /Documentation/DocBook | |
parent | fd7e9a88348472521d999434ee02f25735c7dadf (diff) | |
parent | bd8562626c8e170691d6457fe4e8dfb45607a48d (diff) | |
download | linux-stable-c1aac62f36c1e37ee81c9e09ee9ee733eef05dcb.tar.gz linux-stable-c1aac62f36c1e37ee81c9e09ee9ee733eef05dcb.tar.bz2 linux-stable-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/Makefile | 5 | ||||
-rw-r--r-- | Documentation/DocBook/deviceiobook.tmpl | 323 | ||||
-rw-r--r-- | Documentation/DocBook/iio.tmpl | 697 | ||||
-rw-r--r-- | Documentation/DocBook/regulator.tmpl | 304 |
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(&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(&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(&dev_lock, flags) -CPU A: ... -CPU A: writel(newval, ring_ptr); -CPU A: spin_unlock_irqrestore(&dev_lock, flags) - ... -CPU B: spin_lock_irqsave(&dev_lock, flags) -CPU B: writel(newval2, ring_ptr); -CPU B: ... -CPU B: spin_unlock_irqrestore(&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(&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(&dev_lock, flags) - ... -CPU B: spin_lock_irqsave(&dev_lock, flags) -CPU B: writel(newval2, ring_ptr); -CPU B: ... -CPU B: mmiowb(); -CPU B: spin_unlock_irqrestore(&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 = &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> |