€•1s      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ'/translations/zh_CN/i2c/slave-interface”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/zh_TW/i2c/slave-interface”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/it_IT/i2c/slave-interface”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/ja_JP/i2c/slave-interface”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/ko_KR/i2c/slave-interface”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/sp_SP/i2c/slave-interface”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ%Linux I2C slave interface description”h]”hŒ%Linux I2C slave interface description”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒA/var/lib/git/docbuild/linux/Documentation/i2c/slave-interface.rst”h KubhŒ	paragraph”“”)”}”(hŒ5by Wolfram Sang <wsa@sang-engineering.com> in 2014-15”h]”(hŒby Wolfram Sang <”…””}”(hh¹hžhhŸNh NubhŒ	reference”“”)”}”(hŒwsa@sang-engineering.com”h]”hŒwsa@sang-engineering.com”…””}”(hhÃhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:wsa@sang-engineering.com”uh1hÁhh¹ubhŒ> in 2014-15”…””}”(hh¹hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hX   Linux can also be an I2C slave if the I2C controller in use has slave
functionality. For that to work, one needs slave support in the bus driver plus
a hardware independent software backend providing the actual functionality. An
example for the latter is the slave-eeprom driver, which acts as a dual memory
driver. While another I2C master on the bus can access it like a regular
EEPROM, the Linux I2C slave can access the content via sysfs and handle data as
needed. The backend driver and the I2C bus driver communicate via events. Here
is a small graph visualizing the data flow and the means by which data is
transported. The dotted line marks only one example. The backend could also
use a character device, be in-kernel only, or something completely different::”h]”hXÿ  Linux can also be an I2C slave if the I2C controller in use has slave
functionality. For that to work, one needs slave support in the bus driver plus
a hardware independent software backend providing the actual functionality. An
example for the latter is the slave-eeprom driver, which acts as a dual memory
driver. While another I2C master on the bus can access it like a regular
EEPROM, the Linux I2C slave can access the content via sysfs and handle data as
needed. The backend driver and the I2C bus driver communicate via events. Here
is a small graph visualizing the data flow and the means by which data is
transported. The dotted line marks only one example. The backend could also
use a character device, be in-kernel only, or something completely different:”…””}”(hhÝhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubhŒliteral_block”“”)”}”(hXò              e.g. sysfs        I2C slave events        I/O registers
+-----------+   v    +---------+     v     +--------+  v  +------------+
| Userspace +........+ Backend +-----------+ Driver +-----+ Controller |
+-----------+        +---------+           +--------+     +------------+
                                                              | |
----------------------------------------------------------------+--  I2C
--------------------------------------------------------------+----  Bus”h]”hXò              e.g. sysfs        I2C slave events        I/O registers
+-----------+   v    +---------+     v     +--------+  v  +------------+
| Userspace +........+ Backend +-----------+ Driver +-----+ Controller |
+-----------+        +---------+           +--------+     +------------+
                                                              | |
----------------------------------------------------------------+--  I2C
--------------------------------------------------------------+----  Bus”…””}”hhísbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1hëhŸh¶h Khh£hžhubh¸)”}”(hŒNote: Technically, there is also the I2C core between the backend and the
driver. However, at this time of writing, the layer is transparent.”h]”hŒNote: Technically, there is also the I2C core between the backend and the
driver. However, at this time of writing, the layer is transparent.”…””}”(hhýhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒUser manual”h]”hŒUser manual”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h K ubh¸)”}”(hX‡  I2C slave backends behave like standard I2C clients. So, you can instantiate
them as described in the document instantiating-devices.rst. The only
difference is that i2c slave backends have their own address space. So, you
have to add 0x1000 to the address you would originally request. An example for
instantiating the slave-eeprom driver from userspace at the 7 bit address 0x64
on bus 1::”h]”hX†  I2C slave backends behave like standard I2C clients. So, you can instantiate
them as described in the document instantiating-devices.rst. The only
difference is that i2c slave backends have their own address space. So, you
have to add 0x1000 to the address you would originally request. An example for
instantiating the slave-eeprom driver from userspace at the 7 bit address 0x64
on bus 1:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K"hj  hžhubhì)”}”(hŒA# echo slave-24c02 0x1064 > /sys/bus/i2c/devices/i2c-1/new_device”h]”hŒA# echo slave-24c02 0x1064 > /sys/bus/i2c/devices/i2c-1/new_device”…””}”hj*  sbah}”(h]”h ]”h"]”h$]”h&]”hûhüuh1hëhŸh¶h K)hj  hžhubh¸)”}”(hŒbEach backend should come with separate documentation to describe its specific
behaviour and setup.”h]”hŒbEach backend should come with separate documentation to describe its specific
behaviour and setup.”…””}”(hj8  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K+hj  hžhubeh}”(h]”Œuser-manual”ah ]”h"]”Œuser manual”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K ubh¢)”}”(hhh]”(h§)”}”(hŒDeveloper manual”h]”hŒDeveloper manual”…””}”(hjQ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjN  hžhhŸh¶h K0ubh¸)”}”(hŒÃFirst, the events which are used by the bus driver and the backend will be
described in detail. After that, some implementation hints for extending bus
drivers and writing backends will be given.”h]”hŒÃFirst, the events which are used by the bus driver and the backend will be
described in detail. After that, some implementation hints for extending bus
drivers and writing backends will be given.”…””}”(hj_  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K2hjN  hžhubh¢)”}”(hhh]”(h§)”}”(hŒI2C slave events”h]”hŒI2C slave events”…””}”(hjp  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjm  hžhhŸh¶h K8ubh¸)”}”(hŒKThe bus driver sends an event to the backend using the following function::”h]”hŒJThe bus driver sends an event to the backend using the following function:”…””}”(hj~  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K:hjm  hžhubhì)”}”(hŒ*ret = i2c_slave_event(client, event, &val)”h]”hŒ*ret = i2c_slave_event(client, event, &val)”…””}”hjŒ  sbah}”(h]”h ]”h"]”h$]”h&]”hûhüuh1hëhŸh¶h K<hjm  hžhubh¸)”}”(hX·  'client' describes the I2C slave device. 'event' is one of the special event
types described hereafter. 'val' holds an u8 value for the data byte to be
read/written and is thus bidirectional. The pointer to val must always be
provided even if val is not used for an event, i.e. don't use NULL here. 'ret'
is the return value from the backend. Mandatory events must be provided by the
bus drivers and must be checked for by backend drivers.”h]”hXÉ  â€˜clientâ€™ describes the I2C slave device. â€˜eventâ€™ is one of the special event
types described hereafter. â€˜valâ€™ holds an u8 value for the data byte to be
read/written and is thus bidirectional. The pointer to val must always be
provided even if val is not used for an event, i.e. donâ€™t use NULL here. â€˜retâ€™
is the return value from the backend. Mandatory events must be provided by the
bus drivers and must be checked for by backend drivers.”…””}”(hjš  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K>hjm  hžhubh¸)”}”(hŒEvent types:”h]”hŒEvent types:”…””}”(hj¨  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KEhjm  hžhubhŒbullet_list”“”)”}”(hhh]”hŒ	list_item”“”)”}”(hŒmI2C_SLAVE_WRITE_REQUESTED (mandatory)

'val': unused

'ret': 0 if the backend is ready, otherwise some errno
”h]”(h¸)”}”(hŒ%I2C_SLAVE_WRITE_REQUESTED (mandatory)”h]”hŒ%I2C_SLAVE_WRITE_REQUESTED (mandatory)”…””}”(hjÁ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KGhj½  ubh¸)”}”(hŒ'val': unused”h]”hŒâ€˜valâ€™: unused”…””}”(hjÏ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KIhj½  ubh¸)”}”(hŒ6'ret': 0 if the backend is ready, otherwise some errno”h]”hŒ:â€˜retâ€™: 0 if the backend is ready, otherwise some errno”…””}”(hjÝ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KKhj½  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j»  hj¸  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ*”uh1j¶  hŸh¶h KGhjm  hžhubh¸)”}”(hXí  Another I2C master wants to write data to us. This event should be sent once
our own address and the write bit was detected. The data did not arrive yet, so
there is nothing to process or return. After returning, the bus driver must
always ack the address phase. If 'ret' is zero, backend initialization or
wakeup is done and further data may be received. If 'ret' is an errno, the bus
driver should nack all incoming bytes until the next stop condition to enforce
a retry of the transmission.”h]”hXõ  Another I2C master wants to write data to us. This event should be sent once
our own address and the write bit was detected. The data did not arrive yet, so
there is nothing to process or return. After returning, the bus driver must
always ack the address phase. If â€˜retâ€™ is zero, backend initialization or
wakeup is done and further data may be received. If â€˜retâ€™ is an errno, the bus
driver should nack all incoming bytes until the next stop condition to enforce
a retry of the transmission.”…””}”(hjù  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KMhjm  hžhubj·  )”}”(hhh]”j¼  )”}”(hŒdI2C_SLAVE_READ_REQUESTED (mandatory)

'val': backend returns first byte to be sent

'ret': always 0
”h]”(h¸)”}”(hŒ$I2C_SLAVE_READ_REQUESTED (mandatory)”h]”hŒ$I2C_SLAVE_READ_REQUESTED (mandatory)”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KUhj
  ubh¸)”}”(hŒ,'val': backend returns first byte to be sent”h]”hŒ0â€˜valâ€™: backend returns first byte to be sent”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KWhj
  ubh¸)”}”(hŒ'ret': always 0”h]”hŒâ€˜retâ€™: always 0”…””}”(hj*  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KYhj
  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j»  hj  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j÷  jø  uh1j¶  hŸh¶h KUhjm  hžhubh¸)”}”(hŒ¼Another I2C master wants to read data from us. This event should be sent once
our own address and the read bit was detected. After returning, the bus driver
should transmit the first byte.”h]”hŒ¼Another I2C master wants to read data from us. This event should be sent once
our own address and the read bit was detected. After returning, the bus driver
should transmit the first byte.”…””}”(hjD  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K[hjm  hžhubj·  )”}”(hhh]”j¼  )”}”(hŒžI2C_SLAVE_WRITE_RECEIVED (mandatory)

'val': bus driver delivers received byte

'ret': 0 if the byte should be acked, some errno if the byte should be nacked
”h]”(h¸)”}”(hŒ$I2C_SLAVE_WRITE_RECEIVED (mandatory)”h]”hŒ$I2C_SLAVE_WRITE_RECEIVED (mandatory)”…””}”(hjY  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K_hjU  ubh¸)”}”(hŒ('val': bus driver delivers received byte”h]”hŒ,â€˜valâ€™: bus driver delivers received byte”…””}”(hjg  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KahjU  ubh¸)”}”(hŒM'ret': 0 if the byte should be acked, some errno if the byte should be nacked”h]”hŒQâ€˜retâ€™: 0 if the byte should be acked, some errno if the byte should be nacked”…””}”(hju  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KchjU  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j»  hjR  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j÷  jø  uh1j¶  hŸh¶h K_hjm  hžhubh¸)”}”(hŒµAnother I2C master has sent a byte to us which needs to be set in 'val'. If 'ret'
is zero, the bus driver should ack this byte. If 'ret' is an errno, then the byte
should be nacked.”h]”hŒÁAnother I2C master has sent a byte to us which needs to be set in â€˜valâ€™. If â€˜retâ€™
is zero, the bus driver should ack this byte. If â€˜retâ€™ is an errno, then the byte
should be nacked.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kehjm  hžhubj·  )”}”(hhh]”j¼  )”}”(hŒcI2C_SLAVE_READ_PROCESSED (mandatory)

'val': backend returns next byte to be sent

'ret': always 0
”h]”(h¸)”}”(hŒ$I2C_SLAVE_READ_PROCESSED (mandatory)”h]”hŒ$I2C_SLAVE_READ_PROCESSED (mandatory)”…””}”(hj¤  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kihj   ubh¸)”}”(hŒ+'val': backend returns next byte to be sent”h]”hŒ/â€˜valâ€™: backend returns next byte to be sent”…””}”(hj²  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kkhj   ubh¸)”}”(hŒ'ret': always 0”h]”hŒâ€˜retâ€™: always 0”…””}”(hjÀ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kmhj   ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j»  hj  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j÷  jø  uh1j¶  hŸh¶h Kihjm  hžhubh¸)”}”(hX3  The bus driver requests the next byte to be sent to another I2C master in
'val'. Important: This does not mean that the previous byte has been acked, it
only means that the previous byte is shifted out to the bus! To ensure seamless
transmission, most hardware requests the next byte when the previous one is
still shifted out. If the master sends NACK and stops reading after the byte
currently shifted out, this byte requested here is never used. It very likely
needs to be sent again on the next I2C_SLAVE_READ_REQUEST, depending a bit on
your backend, though.”h]”hX7  The bus driver requests the next byte to be sent to another I2C master in
â€˜valâ€™. Important: This does not mean that the previous byte has been acked, it
only means that the previous byte is shifted out to the bus! To ensure seamless
transmission, most hardware requests the next byte when the previous one is
still shifted out. If the master sends NACK and stops reading after the byte
currently shifted out, this byte requested here is never used. It very likely
needs to be sent again on the next I2C_SLAVE_READ_REQUEST, depending a bit on
your backend, though.”…””}”(hjÚ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kohjm  hžhubj·  )”}”(hhh]”j¼  )”}”(hŒ;I2C_SLAVE_STOP (mandatory)

'val': unused

'ret': always 0
”h]”(h¸)”}”(hŒI2C_SLAVE_STOP (mandatory)”h]”hŒI2C_SLAVE_STOP (mandatory)”…””}”(hjï  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kxhjë  ubh¸)”}”(hŒ'val': unused”h]”hŒâ€˜valâ€™: unused”…””}”(hjý  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kzhjë  ubh¸)”}”(hŒ'ret': always 0”h]”hŒâ€˜retâ€™: always 0”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K|hjë  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j»  hjè  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j÷  jø  uh1j¶  hŸh¶h Kxhjm  hžhubh¸)”}”(hŒ›A stop condition was received. This can happen anytime and the backend should
reset its state machine for I2C transfers to be able to receive new requests.”h]”hŒ›A stop condition was received. This can happen anytime and the backend should
reset its state machine for I2C transfers to be able to receive new requests.”…””}”(hj%  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K~hjm  hžhubeh}”(h]”Œi2c-slave-events”ah ]”h"]”Œi2c slave events”ah$]”h&]”uh1h¡hjN  hžhhŸh¶h K8ubh¢)”}”(hhh]”(h§)”}”(hŒSoftware backends”h]”hŒSoftware backends”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj;  hžhhŸh¶h Kƒubh¸)”}”(hŒ(If you want to write a software backend:”h]”hŒ(If you want to write a software backend:”…””}”(hjL  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K…hj;  hžhubj·  )”}”(hhh]”(j¼  )”}”(hŒ5use a standard i2c_driver and its matching mechanisms”h]”h¸)”}”(hj_  h]”hŒ5use a standard i2c_driver and its matching mechanisms”…””}”(hja  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K‡hj]  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hjZ  hžhhŸh¶h Nubj¼  )”}”(hŒZwrite the slave_callback which handles the above slave events
(best using a state machine)”h]”h¸)”}”(hŒZwrite the slave_callback which handles the above slave events
(best using a state machine)”h]”hŒZwrite the slave_callback which handles the above slave events
(best using a state machine)”…””}”(hjx  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kˆhjt  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hjZ  hžhhŸh¶h Nubj¼  )”}”(hŒ0register this callback via i2c_slave_register()
”h]”h¸)”}”(hŒ/register this callback via i2c_slave_register()”h]”hŒ/register this callback via i2c_slave_register()”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KŠhjŒ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hjZ  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j÷  jø  uh1j¶  hŸh¶h K‡hj;  hžhubh¸)”}”(hŒ0Check the i2c-slave-eeprom driver as an example.”h]”hŒ0Check the i2c-slave-eeprom driver as an example.”…””}”(hjª  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KŒhj;  hžhubeh}”(h]”Œsoftware-backends”ah ]”h"]”Œsoftware backends”ah$]”h&]”uh1h¡hjN  hžhhŸh¶h Kƒubh¢)”}”(hhh]”(h§)”}”(hŒBus driver support”h]”hŒBus driver support”…””}”(hjÃ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÀ  hžhhŸh¶h Kubh¸)”}”(hŒ3If you want to add slave support to the bus driver:”h]”hŒ3If you want to add slave support to the bus driver:”…””}”(hjÑ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K’hjÀ  hžhubj·  )”}”(hhh]”(j¼  )”}”(hX’  implement calls to register/unregister the slave and add those to the
struct i2c_algorithm. When registering, you probably need to set the I2C
slave address and enable slave specific interrupts. If you use runtime pm, you
should use pm_runtime_get_sync() because your device usually needs to be
powered on always to be able to detect its slave address. When unregistering,
do the inverse of the above.
”h]”h¸)”}”(hX‘  implement calls to register/unregister the slave and add those to the
struct i2c_algorithm. When registering, you probably need to set the I2C
slave address and enable slave specific interrupts. If you use runtime pm, you
should use pm_runtime_get_sync() because your device usually needs to be
powered on always to be able to detect its slave address. When unregistering,
do the inverse of the above.”h]”hX‘  implement calls to register/unregister the slave and add those to the
struct i2c_algorithm. When registering, you probably need to set the I2C
slave address and enable slave specific interrupts. If you use runtime pm, you
should use pm_runtime_get_sync() because your device usually needs to be
powered on always to be able to detect its slave address. When unregistering,
do the inverse of the above.”…””}”(hjæ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K”hjâ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hjß  hžhhŸh¶h Nubj¼  )”}”(hŒQCatch the slave interrupts and send appropriate i2c_slave_events to the backend.
”h]”h¸)”}”(hŒPCatch the slave interrupts and send appropriate i2c_slave_events to the backend.”h]”hŒPCatch the slave interrupts and send appropriate i2c_slave_events to the backend.”…””}”(hjþ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K›hjú  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hjß  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j÷  jø  uh1j¶  hŸh¶h K”hjÀ  hžhubh¸)”}”(hŒøNote that most hardware supports being master _and_ slave on the same bus. So,
if you extend a bus driver, please make sure that the driver supports that as
well. In almost all cases, slave support does not need to disable the master
functionality.”h]”hŒøNote that most hardware supports being master _and_ slave on the same bus. So,
if you extend a bus driver, please make sure that the driver supports that as
well. In almost all cases, slave support does not need to disable the master
functionality.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhjÀ  hžhubh¸)”}”(hŒ(Check the i2c-rcar driver as an example.”h]”hŒ(Check the i2c-rcar driver as an example.”…””}”(hj&  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¢hjÀ  hžhubeh}”(h]”Œbus-driver-support”ah ]”h"]”Œbus driver support”ah$]”h&]”uh1h¡hjN  hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒAbout ACK/NACK”h]”hŒAbout ACK/NACK”…””}”(hj?  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj<  hžhhŸh¶h K¦ubh¸)”}”(hXÜ  It is good behaviour to always ACK the address phase, so the master knows if a
device is basically present or if it mysteriously disappeared. Using NACK to
state being busy is troublesome. SMBus demands to always ACK the address phase,
while the I2C specification is more loose on that. Most I2C controllers also
automatically ACK when detecting their slave addresses, so there is no option
to NACK them. For those reasons, this API does not support NACK in the address
phase.”h]”hXÜ  It is good behaviour to always ACK the address phase, so the master knows if a
device is basically present or if it mysteriously disappeared. Using NACK to
state being busy is troublesome. SMBus demands to always ACK the address phase,
while the I2C specification is more loose on that. Most I2C controllers also
automatically ACK when detecting their slave addresses, so there is no option
to NACK them. For those reasons, this API does not support NACK in the address
phase.”…””}”(hjM  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¨hj<  hžhubh¸)”}”(hXu  Currently, there is no slave event to report if the master did ACK or NACK a
byte when it reads from us. We could make this an optional event if the need
arises. However, cases should be extremely rare because the master is expected
to send STOP after that and we have an event for that. Also, keep in mind not
all I2C controllers have the possibility to report that event.”h]”hXu  Currently, there is no slave event to report if the master did ACK or NACK a
byte when it reads from us. We could make this an optional event if the need
arises. However, cases should be extremely rare because the master is expected
to send STOP after that and we have an event for that. Also, keep in mind not
all I2C controllers have the possibility to report that event.”…””}”(hj[  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K°hj<  hžhubeh}”(h]”Œabout-ack-nack”ah ]”h"]”Œabout ack/nack”ah$]”h&]”uh1h¡hjN  hžhhŸh¶h K¦ubh¢)”}”(hhh]”(h§)”}”(hŒAbout buffers”h]”hŒAbout buffers”…””}”(hjt  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjq  hžhhŸh¶h K¸ubh¸)”}”(hŒàDuring development of this API, the question of using buffers instead of just
bytes came up. Such an extension might be possible, usefulness is unclear at
this time of writing. Some points to keep in mind when using buffers:”h]”hŒàDuring development of this API, the question of using buffers instead of just
bytes came up. Such an extension might be possible, usefulness is unclear at
this time of writing. Some points to keep in mind when using buffers:”…””}”(hj‚  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kºhjq  hžhubj·  )”}”(hhh]”(j¼  )”}”(hŒ¯Buffers should be opt-in and backend drivers will always have to support
byte-based transactions as the ultimate fallback anyhow because this is how
the majority of HW works.
”h]”h¸)”}”(hŒ®Buffers should be opt-in and backend drivers will always have to support
byte-based transactions as the ultimate fallback anyhow because this is how
the majority of HW works.”h]”hŒ®Buffers should be opt-in and backend drivers will always have to support
byte-based transactions as the ultimate fallback anyhow because this is how
the majority of HW works.”…””}”(hj—  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¾hj“  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hj  hžhhŸh¶h Nubj¼  )”}”(hX  For backends simulating hardware registers, buffers are largely not helpful
because after each byte written an action should be immediately triggered.
For reads, the data kept in the buffer might get stale if the backend just
updated a register because of internal processing.
”h]”h¸)”}”(hX  For backends simulating hardware registers, buffers are largely not helpful
because after each byte written an action should be immediately triggered.
For reads, the data kept in the buffer might get stale if the backend just
updated a register because of internal processing.”h]”hX  For backends simulating hardware registers, buffers are largely not helpful
because after each byte written an action should be immediately triggered.
For reads, the data kept in the buffer might get stale if the backend just
updated a register because of internal processing.”…””}”(hj¯  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÂhj«  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hj  hžhhŸh¶h Nubj¼  )”}”(hŒžA master can send STOP at any time. For partially transferred buffers, this
means additional code to handle this exception. Such code tends to be
error-prone.”h]”h¸)”}”(hŒžA master can send STOP at any time. For partially transferred buffers, this
means additional code to handle this exception. Such code tends to be
error-prone.”h]”hŒžA master can send STOP at any time. For partially transferred buffers, this
means additional code to handle this exception. Such code tends to be
error-prone.”…””}”(hjÇ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÇhjÃ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j»  hj  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j÷  jø  uh1j¶  hŸh¶h K¾hjq  hžhubeh}”(h]”Œabout-buffers”ah ]”h"]”Œabout buffers”ah$]”h&]”uh1h¡hjN  hžhhŸh¶h K¸ubeh}”(h]”Œdeveloper-manual”ah ]”h"]”Œdeveloper manual”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K0ubeh}”(h]”Œ%linux-i2c-slave-interface-description”ah ]”h"]”Œ%linux i2c slave interface description”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h¶Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(jö  jó  jK  jH  jî  jë  j8  j5  j½  jº  j9  j6  jn  jk  jæ  jã  uŒ	nametypes”}”(jö  ‰jK  ‰jî  ‰j8  ‰j½  ‰j9  ‰jn  ‰jæ  ‰uh}”(jó  h£jH  j  jë  jN  j5  jm  jº  j;  j6  jÀ  jk  j<  jã  jq  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.