diff options
Diffstat (limited to 'Documentation/DocBook')
| -rw-r--r-- | Documentation/DocBook/Makefile | 55 | ||||
| -rw-r--r-- | Documentation/DocBook/alsa-driver-api.tmpl | 2 | ||||
| -rw-r--r-- | Documentation/DocBook/crypto-API.tmpl | 8 | ||||
| -rw-r--r-- | Documentation/DocBook/device-drivers.tmpl | 1 | ||||
| -rw-r--r-- | Documentation/DocBook/filesystems.tmpl | 178 | ||||
| -rw-r--r-- | Documentation/DocBook/iio.tmpl | 697 | ||||
| -rw-r--r-- | Documentation/DocBook/stylesheet.xsl | 1 |
7 files changed, 808 insertions, 134 deletions
diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index b6a6a2e0dd3b..93eff64387cd 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -15,7 +15,7 @@ DOCBOOKS := z8530book.xml device-drivers.xml \ 80211.xml debugobjects.xml sh.xml regulator.xml \ alsa-driver-api.xml writing-an-alsa-driver.xml \ tracepoint.xml drm.xml media_api.xml w1.xml \ - writing_musb_glue_layer.xml crypto-API.xml + writing_musb_glue_layer.xml crypto-API.xml iio.xml include Documentation/DocBook/media/Makefile @@ -56,16 +56,19 @@ htmldocs: $(HTML) MAN := $(patsubst %.xml, %.9, $(BOOKS)) mandocs: $(MAN) - find $(obj)/man -name '*.9' | xargs gzip -f + find $(obj)/man -name '*.9' | xargs gzip -nf installmandocs: mandocs mkdir -p /usr/local/man/man9/ - install $(obj)/man/*.9.gz /usr/local/man/man9/ + find $(obj)/man -name '*.9.gz' -printf '%h %f\n' | \ + sort -k 2 -k 1 | uniq -f 1 | sed -e 's: :/:' | \ + xargs install -m 644 -t /usr/local/man/man9/ ### #External programs used -KERNELDOC = $(srctree)/scripts/kernel-doc -DOCPROC = $(objtree)/scripts/docproc +KERNELDOCXMLREF = $(srctree)/scripts/kernel-doc-xml-ref +KERNELDOC = $(srctree)/scripts/kernel-doc +DOCPROC = $(objtree)/scripts/docproc XMLTOFLAGS = -m $(srctree)/$(src)/stylesheet.xsl XMLTOFLAGS += --skip-validation @@ -89,7 +92,7 @@ define rule_docproc ) > $(dir $@).$(notdir $@).cmd endef -%.xml: %.tmpl $(KERNELDOC) $(DOCPROC) FORCE +%.xml: %.tmpl $(KERNELDOC) $(DOCPROC) $(KERNELDOCXMLREF) FORCE $(call if_changed_rule,docproc) # Tell kbuild to always build the programs @@ -140,7 +143,20 @@ quiet_cmd_db2html = HTML $@ echo '<a HREF="$(patsubst %.html,%,$(notdir $@))/index.html"> \ $(patsubst %.html,%,$(notdir $@))</a><p>' > $@ -%.html: %.xml +### +# Rules to create an aux XML and .db, and use them to re-process the DocBook XML +# to fill internal hyperlinks + gen_aux_xml = : + quiet_gen_aux_xml = echo ' XMLREF $@' +silent_gen_aux_xml = : +%.aux.xml: %.xml + @$($(quiet)gen_aux_xml) + @rm -rf $@ + @(cat $< | egrep "^<refentry id" | egrep -o "\".*\"" | cut -f 2 -d \" > $<.db) + @$(KERNELDOCXMLREF) -db $<.db $< > $@ +.PRECIOUS: %.aux.xml + +%.html: %.aux.xml @(which xmlto > /dev/null 2>&1) || \ (echo "*** You need to install xmlto ***"; \ exit 1) @@ -150,12 +166,12 @@ quiet_cmd_db2html = HTML $@ cp $(PNG-$(basename $(notdir $@))) $(patsubst %.html,%,$@); fi quiet_cmd_db2man = MAN $@ - cmd_db2man = if grep -q refentry $<; then xmlto man $(XMLTOFLAGS) -o $(obj)/man $< ; fi + cmd_db2man = if grep -q refentry $<; then xmlto man $(XMLTOFLAGS) -o $(obj)/man/$(*F) $< ; fi %.9 : %.xml @(which xmlto > /dev/null 2>&1) || \ (echo "*** You need to install xmlto ***"; \ exit 1) - $(Q)mkdir -p $(obj)/man + $(Q)mkdir -p $(obj)/man/$(*F) $(call cmd,db2man) @touch $@ @@ -209,15 +225,18 @@ dochelp: ### # Temporary files left by various tools clean-files := $(DOCBOOKS) \ - $(patsubst %.xml, %.dvi, $(DOCBOOKS)) \ - $(patsubst %.xml, %.aux, $(DOCBOOKS)) \ - $(patsubst %.xml, %.tex, $(DOCBOOKS)) \ - $(patsubst %.xml, %.log, $(DOCBOOKS)) \ - $(patsubst %.xml, %.out, $(DOCBOOKS)) \ - $(patsubst %.xml, %.ps, $(DOCBOOKS)) \ - $(patsubst %.xml, %.pdf, $(DOCBOOKS)) \ - $(patsubst %.xml, %.html, $(DOCBOOKS)) \ - $(patsubst %.xml, %.9, $(DOCBOOKS)) \ + $(patsubst %.xml, %.dvi, $(DOCBOOKS)) \ + $(patsubst %.xml, %.aux, $(DOCBOOKS)) \ + $(patsubst %.xml, %.tex, $(DOCBOOKS)) \ + $(patsubst %.xml, %.log, $(DOCBOOKS)) \ + $(patsubst %.xml, %.out, $(DOCBOOKS)) \ + $(patsubst %.xml, %.ps, $(DOCBOOKS)) \ + $(patsubst %.xml, %.pdf, $(DOCBOOKS)) \ + $(patsubst %.xml, %.html, $(DOCBOOKS)) \ + $(patsubst %.xml, %.9, $(DOCBOOKS)) \ + $(patsubst %.xml, %.aux.xml, $(DOCBOOKS)) \ + $(patsubst %.xml, %.xml.db, $(DOCBOOKS)) \ + $(patsubst %.xml, %.xml, $(DOCBOOKS)) \ $(index) clean-dirs := $(patsubst %.xml,%,$(DOCBOOKS)) man diff --git a/Documentation/DocBook/alsa-driver-api.tmpl b/Documentation/DocBook/alsa-driver-api.tmpl index 71f9246127ec..e94a10bb4a9e 100644 --- a/Documentation/DocBook/alsa-driver-api.tmpl +++ b/Documentation/DocBook/alsa-driver-api.tmpl @@ -108,7 +108,7 @@ <sect1><title>ASoC Core API</title> !Iinclude/sound/soc.h !Esound/soc/soc-core.c -!Esound/soc/soc-cache.c +<!-- !Esound/soc/soc-cache.c no docbook comments here --> !Esound/soc/soc-devres.c !Esound/soc/soc-io.c !Esound/soc/soc-pcm.c diff --git a/Documentation/DocBook/crypto-API.tmpl b/Documentation/DocBook/crypto-API.tmpl index 0992531ffefb..07df23ea06e4 100644 --- a/Documentation/DocBook/crypto-API.tmpl +++ b/Documentation/DocBook/crypto-API.tmpl @@ -585,7 +585,7 @@ kernel crypto API | IPSEC Layer +-----------+ | | | (1) | aead | <----------------------------------- esp_output -| (seqniv) | ---+ +| (seqiv) | ---+ +-----------+ | | (2) +-----------+ | @@ -1101,7 +1101,7 @@ kernel crypto API | Caller </para> <para> - [1] http://www.chronox.de/libkcapi.html + [1] <ulink url="http://www.chronox.de/libkcapi.html">http://www.chronox.de/libkcapi.html</ulink> </para> </sect1> @@ -1661,7 +1661,7 @@ read(opfd, out, outlen); </para> <para> - [1] http://www.chronox.de/libkcapi.html + [1] <ulink url="http://www.chronox.de/libkcapi.html">http://www.chronox.de/libkcapi.html</ulink> </para> </sect1> @@ -1687,7 +1687,7 @@ read(opfd, out, outlen); !Pinclude/linux/crypto.h Block Cipher Algorithm Definitions !Finclude/linux/crypto.h crypto_alg !Finclude/linux/crypto.h ablkcipher_alg -!Finclude/linux/crypto.h aead_alg +!Finclude/crypto/aead.h aead_alg !Finclude/linux/crypto.h blkcipher_alg !Finclude/linux/crypto.h cipher_alg !Finclude/crypto/rng.h rng_alg diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl index faf09d4a0ea8..bbc1d7ee9c76 100644 --- a/Documentation/DocBook/device-drivers.tmpl +++ b/Documentation/DocBook/device-drivers.tmpl @@ -66,6 +66,7 @@ !Ekernel/time/hrtimer.c </sect1> <sect1><title>Workqueues and Kevents</title> +!Iinclude/linux/workqueue.h !Ekernel/workqueue.c </sect1> <sect1><title>Internal Functions</title> diff --git a/Documentation/DocBook/filesystems.tmpl b/Documentation/DocBook/filesystems.tmpl index bcdfdb9a9277..6006b6358c86 100644 --- a/Documentation/DocBook/filesystems.tmpl +++ b/Documentation/DocBook/filesystems.tmpl @@ -146,36 +146,30 @@ The journalling layer is easy to use. You need to first of all create a journal_t data structure. There are two calls to do this dependent on how you decide to allocate the physical -media on which the journal resides. The journal_init_inode() call -is for journals stored in filesystem inodes, or the journal_init_dev() -call can be use for journal stored on a raw device (in a continuous range +media on which the journal resides. The jbd2_journal_init_inode() call +is for journals stored in filesystem inodes, or the jbd2_journal_init_dev() +call can be used for journal stored on a raw device (in a continuous range of blocks). A journal_t is a typedef for a struct pointer, so when -you are finally finished make sure you call journal_destroy() on it +you are finally finished make sure you call jbd2_journal_destroy() on it to free up any used kernel memory. </para> <para> Once you have got your journal_t object you need to 'mount' or load the journal -file, unless of course you haven't initialised it yet - in which case you -need to call journal_create(). +file. The journalling layer expects the space for the journal was already +allocated and initialized properly by the userspace tools. When loading the +journal you must call jbd2_journal_load() to process journal contents. If the +client file system detects the journal contents does not need to be processed +(or even need not have valid contents), it may call jbd2_journal_wipe() to +clear the journal contents before calling jbd2_journal_load(). </para> <para> -Most of the time however your journal file will already have been created, but -before you load it you must call journal_wipe() to empty the journal file. -Hang on, you say , what if the filesystem wasn't cleanly umount()'d . Well, it is the -job of the client file system to detect this and skip the call to journal_wipe(). -</para> - -<para> -In either case the next call should be to journal_load() which prepares the -journal file for use. Note that journal_wipe(..,0) calls journal_skip_recovery() -for you if it detects any outstanding transactions in the journal and similarly -journal_load() will call journal_recover() if necessary. -I would advise reading fs/ext3/super.c for examples on this stage. -[RGG: Why is the journal_wipe() call necessary - doesn't this needlessly -complicate the API. Or isn't a good idea for the journal layer to hide -dirty mounts from the client fs] +Note that jbd2_journal_wipe(..,0) calls jbd2_journal_skip_recovery() for you if +it detects any outstanding transactions in the journal and similarly +jbd2_journal_load() will call jbd2_journal_recover() if necessary. I would +advise reading ext4_load_journal() in fs/ext4/super.c for examples on this +stage. </para> <para> @@ -189,41 +183,41 @@ You still need to actually journal your filesystem changes, this is done by wrapping them into transactions. Additionally you also need to wrap the modification of each of the buffers with calls to the journal layer, so it knows what the modifications -you are actually making are. To do this use journal_start() which +you are actually making are. To do this use jbd2_journal_start() which returns a transaction handle. </para> <para> -journal_start() -and its counterpart journal_stop(), which indicates the end of a transaction -are nestable calls, so you can reenter a transaction if necessary, -but remember you must call journal_stop() the same number of times as -journal_start() before the transaction is completed (or more accurately -leaves the update phase). Ext3/VFS makes use of this feature to simplify -quota support. +jbd2_journal_start() +and its counterpart jbd2_journal_stop(), which indicates the end of a +transaction are nestable calls, so you can reenter a transaction if necessary, +but remember you must call jbd2_journal_stop() the same number of times as +jbd2_journal_start() before the transaction is completed (or more accurately +leaves the update phase). Ext4/VFS makes use of this feature to simplify +handling of inode dirtying, quota support, etc. </para> <para> Inside each transaction you need to wrap the modifications to the individual buffers (blocks). Before you start to modify a buffer you -need to call journal_get_{create,write,undo}_access() as appropriate, +need to call jbd2_journal_get_{create,write,undo}_access() as appropriate, this allows the journalling layer to copy the unmodified data if it needs to. After all the buffer may be part of a previously uncommitted transaction. At this point you are at last ready to modify a buffer, and once -you are have done so you need to call journal_dirty_{meta,}data(). +you are have done so you need to call jbd2_journal_dirty_{meta,}data(). Or if you've asked for access to a buffer you now know is now longer -required to be pushed back on the device you can call journal_forget() +required to be pushed back on the device you can call jbd2_journal_forget() in much the same way as you might have used bforget() in the past. </para> <para> -A journal_flush() may be called at any time to commit and checkpoint +A jbd2_journal_flush() may be called at any time to commit and checkpoint all your transactions. </para> <para> -Then at umount time , in your put_super() you can then call journal_destroy() +Then at umount time , in your put_super() you can then call jbd2_journal_destroy() to clean up your in-core journal object. </para> @@ -231,53 +225,68 @@ to clean up your in-core journal object. Unfortunately there a couple of ways the journal layer can cause a deadlock. The first thing to note is that each task can only have a single outstanding transaction at any one time, remember nothing -commits until the outermost journal_stop(). This means +commits until the outermost jbd2_journal_stop(). This means you must complete the transaction at the end of each file/inode/address etc. operation you perform, so that the journalling system isn't re-entered on another journal. Since transactions can't be nested/batched across differing journals, and another filesystem other than -yours (say ext3) may be modified in a later syscall. +yours (say ext4) may be modified in a later syscall. </para> <para> -The second case to bear in mind is that journal_start() can +The second case to bear in mind is that jbd2_journal_start() can block if there isn't enough space in the journal for your transaction (based on the passed nblocks param) - when it blocks it merely(!) needs to wait for transactions to complete and be committed from other tasks, -so essentially we are waiting for journal_stop(). So to avoid -deadlocks you must treat journal_start/stop() as if they +so essentially we are waiting for jbd2_journal_stop(). So to avoid +deadlocks you must treat jbd2_journal_start/stop() as if they were semaphores and include them in your semaphore ordering rules to prevent -deadlocks. Note that journal_extend() has similar blocking behaviour to -journal_start() so you can deadlock here just as easily as on journal_start(). +deadlocks. Note that jbd2_journal_extend() has similar blocking behaviour to +jbd2_journal_start() so you can deadlock here just as easily as on +jbd2_journal_start(). </para> <para> Try to reserve the right number of blocks the first time. ;-). This will be the maximum number of blocks you are going to touch in this transaction. -I advise having a look at at least ext3_jbd.h to see the basis on which -ext3 uses to make these decisions. +I advise having a look at at least ext4_jbd.h to see the basis on which +ext4 uses to make these decisions. </para> <para> Another wriggle to watch out for is your on-disk block allocation strategy. -why? Because, if you undo a delete, you need to ensure you haven't reused any -of the freed blocks in a later transaction. One simple way of doing this -is make sure any blocks you allocate only have checkpointed transactions -listed against them. Ext3 does this in ext3_test_allocatable(). +Why? Because, if you do a delete, you need to ensure you haven't reused any +of the freed blocks until the transaction freeing these blocks commits. If you +reused these blocks and crash happens, there is no way to restore the contents +of the reallocated blocks at the end of the last fully committed transaction. + +One simple way of doing this is to mark blocks as free in internal in-memory +block allocation structures only after the transaction freeing them commits. +Ext4 uses journal commit callback for this purpose. +</para> + +<para> +With journal commit callbacks you can ask the journalling layer to call a +callback function when the transaction is finally committed to disk, so that +you can do some of your own management. You ask the journalling layer for +calling the callback by simply setting journal->j_commit_callback function +pointer and that function is called after each transaction commit. You can also +use transaction->t_private_list for attaching entries to a transaction that +need processing when the transaction commits. </para> <para> -Lock is also providing through journal_{un,}lock_updates(), -ext3 uses this when it wants a window with a clean and stable fs for a moment. -eg. +JBD2 also provides a way to block all transaction updates via +jbd2_journal_{un,}lock_updates(). Ext4 uses this when it wants a window with a +clean and stable fs for a moment. E.g. </para> <programlisting> - journal_lock_updates() //stop new stuff happening.. - journal_flush() // checkpoint everything. + jbd2_journal_lock_updates() //stop new stuff happening.. + jbd2_journal_flush() // checkpoint everything. ..do stuff on stable fs - journal_unlock_updates() // carry on with filesystem use. + jbd2_journal_unlock_updates() // carry on with filesystem use. </programlisting> <para> @@ -286,29 +295,6 @@ if you allow unprivileged userspace to trigger codepaths containing these calls. </para> -<para> -A new feature of jbd since 2.5.25 is commit callbacks with the new -journal_callback_set() function you can now ask the journalling layer -to call you back when the transaction is finally committed to disk, so that -you can do some of your own management. The key to this is the journal_callback -struct, this maintains the internal callback information but you can -extend it like this:- -</para> -<programlisting> - struct myfs_callback_s { - //Data structure element required by jbd.. - struct journal_callback for_jbd; - // Stuff for myfs allocated together. - myfs_inode* i_commited; - - } -</programlisting> - -<para> -this would be useful if you needed to know when data was committed to a -particular inode. -</para> - </sect2> <sect2 id="jbd_summary"> @@ -319,36 +305,6 @@ being each mount, each modification (transaction) and each changed buffer to tell the journalling layer about them. </para> -<para> -Here is a some pseudo code to give you an idea of how it works, as -an example. -</para> - -<programlisting> - journal_t* my_jnrl = journal_create(); - journal_init_{dev,inode}(jnrl,...) - if (clean) journal_wipe(); - journal_load(); - - foreach(transaction) { /*transactions must be - completed before - a syscall returns to - userspace*/ - - handle_t * xct=journal_start(my_jnrl); - foreach(bh) { - journal_get_{create,write,undo}_access(xact,bh); - if ( myfs_modify(bh) ) { /* returns true - if makes changes */ - journal_dirty_{meta,}data(xact,bh); - } else { - journal_forget(bh); - } - } - journal_stop(xct); - } - journal_destroy(my_jrnl); -</programlisting> </sect2> </sect1> @@ -357,13 +313,13 @@ an example. <title>Data Types</title> <para> The journalling layer uses typedefs to 'hide' the concrete definitions - of the structures used. As a client of the JBD layer you can + of the structures used. As a client of the JBD2 layer you can just rely on the using the pointer as a magic cookie of some sort. Obviously the hiding is not enforced as this is 'C'. </para> <sect2 id="structures"><title>Structures</title> -!Iinclude/linux/jbd.h +!Iinclude/linux/jbd2.h </sect2> </sect1> @@ -375,11 +331,11 @@ an example. manage transactions </para> <sect2 id="journal_level"><title>Journal Level</title> -!Efs/jbd/journal.c -!Ifs/jbd/recovery.c +!Efs/jbd2/journal.c +!Ifs/jbd2/recovery.c </sect2> <sect2 id="transaction_level"><title>Transasction Level</title> -!Efs/jbd/transaction.c +!Efs/jbd2/transaction.c </sect2> </sect1> <sect1 id="see_also"> diff --git a/Documentation/DocBook/iio.tmpl b/Documentation/DocBook/iio.tmpl new file mode 100644 index 000000000000..06bb53de5a47 --- /dev/null +++ b/Documentation/DocBook/iio.tmpl @@ -0,0 +1,697 @@ +<?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, + .storgebits = 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/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(); + 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/stylesheet.xsl b/Documentation/DocBook/stylesheet.xsl index 85b25275196f..3bf4ecf3d760 100644 --- a/Documentation/DocBook/stylesheet.xsl +++ b/Documentation/DocBook/stylesheet.xsl @@ -5,6 +5,7 @@ <param name="funcsynopsis.tabular.threshold">80</param> <param name="callout.graphics">0</param> <!-- <param name="paper.type">A4</param> --> +<param name="generate.consistent.ids">1</param> <param name="generate.section.toc.level">2</param> <param name="use.id.as.filename">1</param> </stylesheet> |