€•â¥Œsphinx.addnodes”Œdocument”“”)”}”(Œ rawsource”Œ”Œchildren”]”(Œ translations”Œ LanguagesNode”“”)”}”(hhh]”(hŒ pending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ refdomain”Œstd”Œreftype”Œdoc”Œ reftarget”Œ'/translations/zh_CN/i2c/writing-clients”Œmodname”NŒ classname”NŒ refexplicit”ˆuŒtagname”hhh ubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ'/translations/zh_TW/i2c/writing-clients”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ'/translations/it_IT/i2c/writing-clients”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ'/translations/ja_JP/i2c/writing-clients”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ'/translations/ko_KR/i2c/writing-clients”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ'/translations/sp_SP/i2c/writing-clients”Œmodname”NŒ classname”NŒ refexplicit”ˆuh1hhh ubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h hhŒ _document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒImplementing I2C device drivers”h]”hŒImplementing I2C device drivers”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒA/var/lib/git/docbuild/linux/Documentation/i2c/writing-clients.rst”h KubhŒ paragraph”“”)”}”(hŒThis is a small guide for those who want to write kernel drivers for I2C or SMBus devices, using Linux as the protocol host/master (not slave).”h]”hŒThis is a small guide for those who want to write kernel drivers for I2C or SMBus devices, using Linux as the protocol host/master (not slave).”…””}”(hh¹hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒ¬To set up a driver, you need to do several things. Some are optional, and some things can be done slightly or completely different. Use this as a guide, not as a rule book!”h]”hŒ¬To set up a driver, you need to do several things. Some are optional, and some things can be done slightly or completely different. Use this as a guide, not as a rule book!”…””}”(hhÇhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒGeneral remarks”h]”hŒGeneral remarks”…””}”(hhØhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhÕhžhhŸh¶h Kubh¸)”}”(hX"Try to keep the kernel namespace as clean as possible. The best way to do this is to use a unique prefix for all global symbols. This is especially important for exported symbols, but it is a good idea to do it for non-exported symbols too. We will use the prefix ``foo_`` in this tutorial.”h]”(hXTry to keep the kernel namespace as clean as possible. The best way to do this is to use a unique prefix for all global symbols. This is especially important for exported symbols, but it is a good idea to do it for non-exported symbols too. We will use the prefix ”…””}”(hhæhžhhŸNh NubhŒliteral”“”)”}”(hŒ``foo_``”h]”hŒfoo_”…””}”(hhðhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hîhhæubhŒ in this tutorial.”…””}”(hhæhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÕhžhubeh}”(h]”Œgeneral-remarks”ah ]”h"]”Œgeneral remarks”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒThe driver structure”h]”hŒThe driver structure”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjhžhhŸh¶h Kubh¸)”}”(hXPUsually, you will implement a single driver structure, and instantiate all clients from it. Remember, a driver structure contains general access routines, and should be zero-initialized except for fields with data you provide. A client structure holds device-specific information like the driver model device node, and its I2C address.”h]”hXPUsually, you will implement a single driver structure, and instantiate all clients from it. Remember, a driver structure contains general access routines, and should be zero-initialized except for fields with data you provide. A client structure holds device-specific information like the driver model device node, and its I2C address.”…””}”(hj!hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhjhžhubhŒ literal_block”“”)”}”(hX%static const struct i2c_device_id foo_idtable[] = { { "foo", my_id_for_foo }, { "bar", my_id_for_bar }, { } }; MODULE_DEVICE_TABLE(i2c, foo_idtable); static struct i2c_driver foo_driver = { .driver = { .name = "foo", .pm = &foo_pm_ops, /* optional */ }, .id_table = foo_idtable, .probe = foo_probe, .remove = foo_remove, .shutdown = foo_shutdown, /* optional */ .command = foo_command, /* optional, deprecated */ }”h]”hX%static const struct i2c_device_id foo_idtable[] = { { "foo", my_id_for_foo }, { "bar", my_id_for_bar }, { } }; MODULE_DEVICE_TABLE(i2c, foo_idtable); static struct i2c_driver foo_driver = { .driver = { .name = "foo", .pm = &foo_pm_ops, /* optional */ }, .id_table = foo_idtable, .probe = foo_probe, .remove = foo_remove, .shutdown = foo_shutdown, /* optional */ .command = foo_command, /* optional, deprecated */ }”…””}”hj1sbah}”(h]”h ]”h"]”h$]”h&]”Œ xml:space”Œpreserve”uh1j/hŸh¶h K"hjhžhubh¸)”}”(hXcThe name field is the driver name, and must not contain spaces. It should match the module name (if the driver can be compiled as a module), although you can use MODULE_ALIAS (passing "foo" in this example) to add another name for the module. If the driver name doesn't match the module name, the module won't be automatically loaded (hotplug/coldplug).”h]”hXkThe name field is the driver name, and must not contain spaces. It should match the module name (if the driver can be compiled as a module), although you can use MODULE_ALIAS (passing “foo†in this example) to add another name for the module. If the driver name doesn’t match the module name, the module won’t be automatically loaded (hotplug/coldplug).”…””}”(hjAhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K7hjhžhubh¸)”}”(hŒKAll other fields are for call-back functions which will be explained below.”h]”hŒKAll other fields are for call-back functions which will be explained below.”…””}”(hjOhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K=hjhžhubeh}”(h]”Œthe-driver-structure”ah ]”h"]”Œthe driver structure”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒExtra client data”h]”hŒExtra client data”…””}”(hjhhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjehžhhŸh¶h KBubh¸)”}”(hŒEach client structure has a special ``data`` field that can point to any structure at all. You should use this to keep device-specific data.”h]”(hŒ$Each client structure has a special ”…””}”(hjvhžhhŸNh Nubhï)”}”(hŒ``data``”h]”hŒdata”…””}”(hj~hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hîhjvubhŒa field that can point to any structure at all. You should use this to keep device-specific data.”…””}”(hjvhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KDhjehžhubj0)”}”(hŒª/* store the value */ void i2c_set_clientdata(struct i2c_client *client, void *data); /* retrieve the value */ void *i2c_get_clientdata(const struct i2c_client *client);”h]”hŒª/* store the value */ void i2c_set_clientdata(struct i2c_client *client, void *data); /* retrieve the value */ void *i2c_get_clientdata(const struct i2c_client *client);”…””}”hj–sbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h KIhjehžhubh¸)”}”(hŒøNote that starting with kernel 2.6.34, you don't have to set the ``data`` field to NULL in remove() or if probe() failed anymore. The i2c-core does this automatically on these occasions. Those are also the only times the core will touch this field.”h]”(hŒCNote that starting with kernel 2.6.34, you don’t have to set the ”…””}”(hj¤hžhhŸNh Nubhï)”}”(hŒ``data``”h]”hŒdata”…””}”(hj¬hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hîhj¤ubhŒ¯ field to NULL in remove() or if probe() failed anymore. The i2c-core does this automatically on these occasions. Those are also the only times the core will touch this field.”…””}”(hj¤hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KOhjehžhubeh}”(h]”Œextra-client-data”ah ]”h"]”Œextra client data”ah$]”h&]”uh1h¡hh£hžhhŸh¶h KBubh¢)”}”(hhh]”(h§)”}”(hŒAccessing the client”h]”hŒAccessing the client”…””}”(hjÏhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÌhžhhŸh¶h KVubh¸)”}”(hŒ•Let's say we have a valid client structure. At some time, we will need to gather information from the client, or write new information to the client.”h]”hŒ—Let’s say we have a valid client structure. At some time, we will need to gather information from the client, or write new information to the client.”…””}”(hjÝhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KXhjÌhžhubh¸)”}”(hŒçI have found it useful to define foo_read and foo_write functions for this. For some cases, it will be easier to call the I2C functions directly, but many chips have some kind of register-value idea that can easily be encapsulated.”h]”hŒçI have found it useful to define foo_read and foo_write functions for this. For some cases, it will be easier to call the I2C functions directly, but many chips have some kind of register-value idea that can easily be encapsulated.”…””}”(hjëhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K\hjÌhžhubh¸)”}”(hŒMThe below functions are simple examples, and should not be copied literally::”h]”hŒLThe below functions are simple examples, and should not be copied literally:”…””}”(hjùhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KahjÌhžhubj0)”}”(hX¶int foo_read_value(struct i2c_client *client, u8 reg) { if (reg < 0x10) /* byte-sized register */ return i2c_smbus_read_byte_data(client, reg); else /* word-sized register */ return i2c_smbus_read_word_data(client, reg); } int foo_write_value(struct i2c_client *client, u8 reg, u16 value) { if (reg == 0x10) /* Impossible to write - driver error! */ return -EINVAL; else if (reg < 0x10) /* byte-sized register */ return i2c_smbus_write_byte_data(client, reg, value); else /* word-sized register */ return i2c_smbus_write_word_data(client, reg, value); }”h]”hX¶int foo_read_value(struct i2c_client *client, u8 reg) { if (reg < 0x10) /* byte-sized register */ return i2c_smbus_read_byte_data(client, reg); else /* word-sized register */ return i2c_smbus_read_word_data(client, reg); } int foo_write_value(struct i2c_client *client, u8 reg, u16 value) { if (reg == 0x10) /* Impossible to write - driver error! */ return -EINVAL; else if (reg < 0x10) /* byte-sized register */ return i2c_smbus_write_byte_data(client, reg, value); else /* word-sized register */ return i2c_smbus_write_word_data(client, reg, value); }”…””}”hjsbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h KdhjÌhžhubeh}”(h]”Œaccessing-the-client”ah ]”h"]”Œaccessing the client”ah$]”h&]”uh1h¡hh£hžhhŸh¶h KVubh¢)”}”(hhh]”(h§)”}”(hŒProbing and attaching”h]”hŒProbing and attaching”…””}”(hj hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjhžhhŸh¶h Kxubh¸)”}”(hX½The Linux I2C stack was originally written to support access to hardware monitoring chips on PC motherboards, and thus used to embed some assumptions that were more appropriate to SMBus (and PCs) than to I2C. One of these assumptions was that most adapters and devices drivers support the SMBUS_QUICK protocol to probe device presence. Another was that devices and their drivers can be sufficiently configured using only such probe primitives.”h]”hX½The Linux I2C stack was originally written to support access to hardware monitoring chips on PC motherboards, and thus used to embed some assumptions that were more appropriate to SMBus (and PCs) than to I2C. One of these assumptions was that most adapters and devices drivers support the SMBUS_QUICK protocol to probe device presence. Another was that devices and their drivers can be sufficiently configured using only such probe primitives.”…””}”(hj.hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kzhjhžhubh¸)”}”(hXœAs Linux and its I2C stack became more widely used in embedded systems and complex components such as DVB adapters, those assumptions became more problematic. Drivers for I2C devices that issue interrupts need more (and different) configuration information, as do drivers handling chip variants that can't be distinguished by protocol probing, or which need some board specific information to operate correctly.”h]”hXžAs Linux and its I2C stack became more widely used in embedded systems and complex components such as DVB adapters, those assumptions became more problematic. Drivers for I2C devices that issue interrupts need more (and different) configuration information, as do drivers handling chip variants that can’t be distinguished by protocol probing, or which need some board specific information to operate correctly.”…””}”(hj<hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khjhžhubh¢)”}”(hhh]”(h§)”}”(hŒDevice/Driver Binding”h]”hŒDevice/Driver Binding”…””}”(hjMhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjJhžhhŸh¶h KŠubh¸)”}”(hX˜System infrastructure, typically board-specific initialization code or boot firmware, reports what I2C devices exist. For example, there may be a table, in the kernel or from the boot loader, identifying I2C devices and linking them to board-specific configuration information about IRQs and other wiring artifacts, chip type, and so on. That could be used to create i2c_client objects for each I2C device.”h]”hX˜System infrastructure, typically board-specific initialization code or boot firmware, reports what I2C devices exist. For example, there may be a table, in the kernel or from the boot loader, identifying I2C devices and linking them to board-specific configuration information about IRQs and other wiring artifacts, chip type, and so on. That could be used to create i2c_client objects for each I2C device.”…””}”(hj[hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KŒhjJhžhubh¸)”}”(hŒ·I2C device drivers using this binding model work just like any other kind of driver in Linux: they provide a probe() method to bind to those devices, and a remove() method to unbind.”h]”hŒ·I2C device drivers using this binding model work just like any other kind of driver in Linux: they provide a probe() method to bind to those devices, and a remove() method to unbind.”…””}”(hjihžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K“hjJhžhubj0)”}”(hŒcstatic int foo_probe(struct i2c_client *client); static void foo_remove(struct i2c_client *client);”h]”hŒcstatic int foo_probe(struct i2c_client *client); static void foo_remove(struct i2c_client *client);”…””}”hjwsbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h K™hjJhžhubh¸)”}”(hX!Remember that the i2c_driver does not create those client handles. The handle may be used during foo_probe(). If foo_probe() reports success (zero not a negative status code) it may save the handle and use it until foo_remove() returns. That binding model is used by most Linux drivers.”h]”hX!Remember that the i2c_driver does not create those client handles. The handle may be used during foo_probe(). If foo_probe() reports success (zero not a negative status code) it may save the handle and use it until foo_remove() returns. That binding model is used by most Linux drivers.”…””}”(hj…hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KœhjJhžhubh¸)”}”(hŒ¡The probe function is called when an entry in the id_table name field matches the device's name. If the probe function needs that entry, it can retrieve it using”h]”hŒ£The probe function is called when an entry in the id_table name field matches the device’s name. If the probe function needs that entry, it can retrieve it using”…””}”(hj“hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¡hjJhžhubj0)”}”(hŒCconst struct i2c_device_id *id = i2c_match_id(foo_idtable, client);”h]”hŒCconst struct i2c_device_id *id = i2c_match_id(foo_idtable, client);”…””}”hj¡sbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h K§hjJhžhubeh}”(h]”Œdevice-driver-binding”ah ]”h"]”Œdevice/driver binding”ah$]”h&]”uh1h¡hjhžhhŸh¶h KŠubh¢)”}”(hhh]”(h§)”}”(hŒDevice Creation”h]”hŒDevice Creation”…””}”(hjºhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj·hžhhŸh¶h K«ubh¸)”}”(hXIf you know for a fact that an I2C device is connected to a given I2C bus, you can instantiate that device by simply filling an i2c_board_info structure with the device address and driver name, and calling i2c_new_client_device(). This will create the device, then the driver core will take care of finding the right driver and will call its probe() method. If a driver supports different device types, you can specify the type you want using the type field. You can also specify an IRQ and platform data if needed.”h]”hXIf you know for a fact that an I2C device is connected to a given I2C bus, you can instantiate that device by simply filling an i2c_board_info structure with the device address and driver name, and calling i2c_new_client_device(). This will create the device, then the driver core will take care of finding the right driver and will call its probe() method. If a driver supports different device types, you can specify the type you want using the type field. You can also specify an IRQ and platform data if needed.”…””}”(hjÈhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K­hj·hžhubh¸)”}”(hX”Sometimes you know that a device is connected to a given I2C bus, but you don't know the exact address it uses. This happens on TV adapters for example, where the same driver supports dozens of slightly different models, and I2C device addresses change from one model to the next. In that case, you can use the i2c_new_scanned_device() variant, which is similar to i2c_new_client_device(), except that it takes an additional list of possible I2C addresses to probe. A device is created for the first responsive address in the list. If you expect more than one device to be present in the address range, simply call i2c_new_scanned_device() that many times.”h]”hX–Sometimes you know that a device is connected to a given I2C bus, but you don’t know the exact address it uses. This happens on TV adapters for example, where the same driver supports dozens of slightly different models, and I2C device addresses change from one model to the next. In that case, you can use the i2c_new_scanned_device() variant, which is similar to i2c_new_client_device(), except that it takes an additional list of possible I2C addresses to probe. A device is created for the first responsive address in the list. If you expect more than one device to be present in the address range, simply call i2c_new_scanned_device() that many times.”…””}”(hjÖhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¶hj·hžhubh¸)”}”(hŒ®The call to i2c_new_client_device() or i2c_new_scanned_device() typically happens in the I2C bus driver. You may want to save the returned i2c_client reference for later use.”h]”hŒ®The call to i2c_new_client_device() or i2c_new_scanned_device() typically happens in the I2C bus driver. You may want to save the returned i2c_client reference for later use.”…””}”(hjähžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÁhj·hžhubeh}”(h]”Œdevice-creation”ah ]”h"]”Œdevice creation”ah$]”h&]”uh1h¡hjhžhhŸh¶h K«ubh¢)”}”(hhh]”(h§)”}”(hŒDevice Detection”h]”hŒDevice Detection”…””}”(hjýhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjúhžhhŸh¶h KÇubh¸)”}”(hXàThe device detection mechanism comes with a number of disadvantages. You need some reliable way to identify the supported devices (typically using device-specific, dedicated identification registers), otherwise misdetections are likely to occur and things can get wrong quickly. Keep in mind that the I2C protocol doesn't include any standard way to detect the presence of a chip at a given address, let alone a standard way to identify devices. Even worse is the lack of semantics associated to bus transfers, which means that the same transfer can be seen as a read operation by a chip and as a write operation by another chip. For these reasons, device detection is considered a legacy mechanism and shouldn't be used in new code.”h]”hXäThe device detection mechanism comes with a number of disadvantages. You need some reliable way to identify the supported devices (typically using device-specific, dedicated identification registers), otherwise misdetections are likely to occur and things can get wrong quickly. Keep in mind that the I2C protocol doesn’t include any standard way to detect the presence of a chip at a given address, let alone a standard way to identify devices. Even worse is the lack of semantics associated to bus transfers, which means that the same transfer can be seen as a read operation by a chip and as a write operation by another chip. For these reasons, device detection is considered a legacy mechanism and shouldn’t be used in new code.”…””}”(hj hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÉhjúhžhubeh}”(h]”Œdevice-detection”ah ]”h"]”Œdevice detection”ah$]”h&]”uh1h¡hjhžhhŸh¶h KÇubh¢)”}”(hhh]”(h§)”}”(hŒDevice Deletion”h]”hŒDevice Deletion”…””}”(hj$hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj!hžhhŸh¶h K×ubh¸)”}”(hXLEach I2C device which has been created using i2c_new_client_device() or i2c_new_scanned_device() can be unregistered by calling i2c_unregister_device(). If you don't call it explicitly, it will be called automatically before the underlying I2C bus itself is removed, as a device can't survive its parent in the device driver model.”h]”hXPEach I2C device which has been created using i2c_new_client_device() or i2c_new_scanned_device() can be unregistered by calling i2c_unregister_device(). If you don’t call it explicitly, it will be called automatically before the underlying I2C bus itself is removed, as a device can’t survive its parent in the device driver model.”…””}”(hj2hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÙhj!hžhubeh}”(h]”Œdevice-deletion”ah ]”h"]”Œdevice deletion”ah$]”h&]”uh1h¡hjhžhhŸh¶h K×ubeh}”(h]”Œprobing-and-attaching”ah ]”h"]”Œprobing and attaching”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kxubh¢)”}”(hhh]”(h§)”}”(hŒInitializing the driver”h]”hŒInitializing the driver”…””}”(hjShžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjPhžhhŸh¶h Káubh¸)”}”(hŒ«When the kernel is booted, or when your foo driver module is inserted, you have to do some initializing. Fortunately, just registering the driver module is usually enough.”h]”hŒ«When the kernel is booted, or when your foo driver module is inserted, you have to do some initializing. Fortunately, just registering the driver module is usually enough.”…””}”(hjahžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KãhjPhžhubj0)”}”(hX-static int __init foo_init(void) { return i2c_add_driver(&foo_driver); } module_init(foo_init); static void __exit foo_cleanup(void) { i2c_del_driver(&foo_driver); } module_exit(foo_cleanup); The module_i2c_driver() macro can be used to reduce above code. module_i2c_driver(foo_driver);”h]”hX-static int __init foo_init(void) { return i2c_add_driver(&foo_driver); } module_init(foo_init); static void __exit foo_cleanup(void) { i2c_del_driver(&foo_driver); } module_exit(foo_cleanup); The module_i2c_driver() macro can be used to reduce above code. module_i2c_driver(foo_driver);”…””}”hjosbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h KéhjPhžhubh¸)”}”(hXNote that some functions are marked by ``__init``. These functions can be removed after kernel booting (or module loading) is completed. Likewise, functions marked by ``__exit`` are dropped by the compiler when the code is built into the kernel, as they would never be called.”h]”(hŒ'Note that some functions are marked by ”…””}”(hj}hžhhŸNh Nubhï)”}”(hŒ ``__init``”h]”hŒ__init”…””}”(hj…hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hîhj}ubhŒw. These functions can be removed after kernel booting (or module loading) is completed. Likewise, functions marked by ”…””}”(hj}hžhhŸNh Nubhï)”}”(hŒ ``__exit``”h]”hŒ__exit”…””}”(hj—hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hîhj}ubhŒc are dropped by the compiler when the code is built into the kernel, as they would never be called.”…””}”(hj}hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KùhjPhžhubeh}”(h]”Œinitializing-the-driver”ah ]”h"]”Œinitializing the driver”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Káubh¢)”}”(hhh]”(h§)”}”(hŒDriver Information”h]”hŒDriver Information”…””}”(hjºhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj·hžhhŸh¶h Mubj0)”}”(hŒç/* Substitute your own name and email address */ MODULE_AUTHOR("Frodo Looijaard " MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices"); /* a few non-GPL license types are also allowed */ MODULE_LICENSE("GPL");”h]”hŒç/* Substitute your own name and email address */ MODULE_AUTHOR("Frodo Looijaard " MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices"); /* a few non-GPL license types are also allowed */ MODULE_LICENSE("GPL");”…””}”hjÈsbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h Mhj·hžhubeh}”(h]”Œdriver-information”ah ]”h"]”Œdriver information”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Mubh¢)”}”(hhh]”(h§)”}”(hŒPower Management”h]”hŒPower Management”…””}”(hjáhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÞhžhhŸh¶h M ubh¸)”}”(hXIf your I2C device needs special handling when entering a system low power state -- like putting a transceiver into a low power mode, or activating a system wakeup mechanism -- do that by implementing the appropriate callbacks for the dev_pm_ops of the driver (like suspend and resume).”h]”hXIf your I2C device needs special handling when entering a system low power state -- like putting a transceiver into a low power mode, or activating a system wakeup mechanism -- do that by implementing the appropriate callbacks for the dev_pm_ops of the driver (like suspend and resume).”…””}”(hjïhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MhjÞhžhubh¸)”}”(hX"These are standard driver model calls, and they work just like they would for any other driver stack. The calls can sleep, and can use I2C messaging to the device being suspended or resumed (since their parent I2C adapter is active when these calls are issued, and IRQs are still enabled).”h]”hX"These are standard driver model calls, and they work just like they would for any other driver stack. The calls can sleep, and can use I2C messaging to the device being suspended or resumed (since their parent I2C adapter is active when these calls are issued, and IRQs are still enabled).”…””}”(hjýhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MhjÞhžhubeh}”(h]”Œpower-management”ah ]”h"]”Œpower management”ah$]”h&]”uh1h¡hh£hžhhŸh¶h M ubh¢)”}”(hhh]”(h§)”}”(hŒSystem Shutdown”h]”hŒSystem Shutdown”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjhžhhŸh¶h Mubh¸)”}”(hŒ›If your I2C device needs special handling when the system shuts down or reboots (including kexec) -- like turning something off -- use a shutdown() method.”h]”hŒ›If your I2C device needs special handling when the system shuts down or reboots (including kexec) -- like turning something off -- use a shutdown() method.”…””}”(hj$hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjhžhubh¸)”}”(hŒ”Again, this is a standard driver model call, working just like it would for any other driver stack: the calls can sleep, and can use I2C messaging.”h]”hŒ”Again, this is a standard driver model call, working just like it would for any other driver stack: the calls can sleep, and can use I2C messaging.”…””}”(hj2hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M#hjhžhubeh}”(h]”Œsystem-shutdown”ah ]”h"]”Œsystem shutdown”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Mubh¢)”}”(hhh]”(h§)”}”(hŒCommand function”h]”hŒCommand function”…””}”(hjKhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjHhžhhŸh¶h M)ubh¸)”}”(hŒ•A generic ioctl-like function call back is supported. You will seldom need this, and its use is deprecated anyway, so newer design should not use it.”h]”hŒ•A generic ioctl-like function call back is supported. You will seldom need this, and its use is deprecated anyway, so newer design should not use it.”…””}”(hjYhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M+hjHhžhubeh}”(h]”Œcommand-function”ah ]”h"]”Œcommand function”ah$]”h&]”uh1h¡hh£hžhhŸh¶h M)ubh¢)”}”(hhh]”(h§)”}”(hŒSending and receiving”h]”hŒSending and receiving”…””}”(hjrhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjohžhhŸh¶h M1ubh¸)”}”(hŒIf you want to communicate with your device, there are several functions to do this. You can find all of them in .”h]”hŒIf you want to communicate with your device, there are several functions to do this. You can find all of them in .”…””}”(hj€hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M3hjohžhubh¸)”}”(hŒÁIf you can choose between plain I2C communication and SMBus level communication, please use the latter. All adapters understand SMBus level commands, but only some of them understand plain I2C!”h]”hŒÁIf you can choose between plain I2C communication and SMBus level communication, please use the latter. All adapters understand SMBus level commands, but only some of them understand plain I2C!”…””}”(hjŽhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M6hjohžhubh¢)”}”(hhh]”(h§)”}”(hŒPlain I2C communication”h]”hŒPlain I2C communication”…””}”(hjŸhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjœhžhhŸh¶h M<ubj0)”}”(hŒ¥int i2c_master_send(struct i2c_client *client, const char *buf, int count); int i2c_master_recv(struct i2c_client *client, char *buf, int count);”h]”hŒ¥int i2c_master_send(struct i2c_client *client, const char *buf, int count); int i2c_master_recv(struct i2c_client *client, char *buf, int count);”…””}”hj­sbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h M@hjœhžhubh¸)”}”(hXzThese routines read and write some bytes from/to a client. The client contains the I2C address, so you do not have to include it. The second parameter contains the bytes to read/write, the third the number of bytes to read/write (must be less than the length of the buffer, also should be less than 64k since msg.len is u16.) Returned is the actual number of bytes read/written.”h]”hXzThese routines read and write some bytes from/to a client. The client contains the I2C address, so you do not have to include it. The second parameter contains the bytes to read/write, the third the number of bytes to read/write (must be less than the length of the buffer, also should be less than 64k since msg.len is u16.) Returned is the actual number of bytes read/written.”…””}”(hj»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MDhjœhžhubj0)”}”(hŒZint i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num);”h]”hŒZint i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num);”…””}”hjÉsbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h MMhjœhžhubh¸)”}”(hX;This sends a series of messages. Each message can be a read or write, and they can be mixed in any way. The transactions are combined: no stop condition is issued between transaction. The i2c_msg structure contains for each message the client address, the number of bytes of the message and the message data itself.”h]”hX;This sends a series of messages. Each message can be a read or write, and they can be mixed in any way. The transactions are combined: no stop condition is issued between transaction. The i2c_msg structure contains for each message the client address, the number of bytes of the message and the message data itself.”…””}”(hj×hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MPhjœhžhubh¸)”}”(hŒZYou can read the file i2c-protocol.rst for more information about the actual I2C protocol.”h]”hŒZYou can read the file i2c-protocol.rst for more information about the actual I2C protocol.”…””}”(hjåhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MVhjœhžhubeh}”(h]”Œplain-i2c-communication”ah ]”h"]”Œplain i2c communication”ah$]”h&]”uh1h¡hjohžhhŸh¶h M<ubh¢)”}”(hhh]”(h§)”}”(hŒSMBus communication”h]”hŒSMBus communication”…””}”(hjþhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjûhžhhŸh¶h M[ubj0)”}”(hŒ¹s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, char read_write, u8 command, int size, union i2c_smbus_data *data);”h]”hŒ¹s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, char read_write, u8 command, int size, union i2c_smbus_data *data);”…””}”hj sbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h M_hjûhžhubh¸)”}”(hŒyThis is the generic SMBus function. All functions below are implemented in terms of it. Never use this function directly!”h]”hŒyThis is the generic SMBus function. All functions below are implemented in terms of it. Never use this function directly!”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mchjûhžhubj0)”}”(hXýs32 i2c_smbus_read_byte(struct i2c_client *client); s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value); s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command); s32 i2c_smbus_write_byte_data(struct i2c_client *client, u8 command, u8 value); s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command); s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value); s32 i2c_smbus_read_block_data(struct i2c_client *client, u8 command, u8 *values); s32 i2c_smbus_write_block_data(struct i2c_client *client, u8 command, u8 length, const u8 *values); s32 i2c_smbus_read_i2c_block_data(struct i2c_client *client, u8 command, u8 length, u8 *values); s32 i2c_smbus_write_i2c_block_data(struct i2c_client *client, u8 command, u8 length, const u8 *values);”h]”hXýs32 i2c_smbus_read_byte(struct i2c_client *client); s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value); s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command); s32 i2c_smbus_write_byte_data(struct i2c_client *client, u8 command, u8 value); s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command); s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value); s32 i2c_smbus_read_block_data(struct i2c_client *client, u8 command, u8 *values); s32 i2c_smbus_write_block_data(struct i2c_client *client, u8 command, u8 length, const u8 *values); s32 i2c_smbus_read_i2c_block_data(struct i2c_client *client, u8 command, u8 length, u8 *values); s32 i2c_smbus_write_i2c_block_data(struct i2c_client *client, u8 command, u8 length, const u8 *values);”…””}”hj(sbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h Mhhjûhžhubh¸)”}”(hŒjThese ones were removed from i2c-core because they had no users, but could be added back later if needed::”h]”hŒiThese ones were removed from i2c-core because they had no users, but could be added back later if needed:”…””}”(hj6hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mzhjûhžhubj0)”}”(hX)s32 i2c_smbus_write_quick(struct i2c_client *client, u8 value); s32 i2c_smbus_process_call(struct i2c_client *client, u8 command, u16 value); s32 i2c_smbus_block_process_call(struct i2c_client *client, u8 command, u8 length, u8 *values);”h]”hX)s32 i2c_smbus_write_quick(struct i2c_client *client, u8 value); s32 i2c_smbus_process_call(struct i2c_client *client, u8 command, u16 value); s32 i2c_smbus_block_process_call(struct i2c_client *client, u8 command, u8 length, u8 *values);”…””}”hjDsbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h M}hjûhžhubh¸)”}”(hXAll these transactions return a negative errno value on failure. The 'write' transactions return 0 on success; the 'read' transactions return the read value, except for block transactions, which return the number of values read. The block buffers need not be longer than 32 bytes.”h]”hX All these transactions return a negative errno value on failure. The ‘write’ transactions return 0 on success; the ‘read’ transactions return the read value, except for block transactions, which return the number of values read. The block buffers need not be longer than 32 bytes.”…””}”(hjRhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mƒhjûhžhubh¸)”}”(hŒ^You can read the file smbus-protocol.rst for more information about the actual SMBus protocol.”h]”hŒ^You can read the file smbus-protocol.rst for more information about the actual SMBus protocol.”…””}”(hj`hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mˆhjûhžhubeh}”(h]”Œsmbus-communication”ah ]”h"]”Œsmbus communication”ah$]”h&]”uh1h¡hjohžhhŸh¶h M[ubeh}”(h]”Œsending-and-receiving”ah ]”h"]”Œsending and receiving”ah$]”h&]”uh1h¡hh£hžhhŸh¶h M1ubh¢)”}”(hhh]”(h§)”}”(hŒGeneral purpose routines”h]”hŒGeneral purpose routines”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj~hžhhŸh¶h Mubh¸)”}”(hŒOBelow all general purpose routines are listed, that were not mentioned before::”h]”hŒNBelow all general purpose routines are listed, that were not mentioned before:”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj~hžhubj0)”}”(hŒd/* Return the adapter number for a specific adapter */ int i2c_adapter_id(struct i2c_adapter *adap);”h]”hŒd/* Return the adapter number for a specific adapter */ int i2c_adapter_id(struct i2c_adapter *adap);”…””}”hjsbah}”(h]”h ]”h"]”h$]”h&]”j?j@uh1j/hŸh¶h M’hj~hžhubeh}”(h]”Œgeneral-purpose-routines”ah ]”h"]”Œgeneral purpose routines”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Mubeh}”(h]”Œimplementing-i2c-device-drivers”ah ]”h"]”Œimplementing i2c device drivers”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒ current_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ generator”NŒ datestamp”NŒ source_link”NŒ source_url”NŒ toc_backlinks”Œentry”Œfootnote_backlinks”KŒ sectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒ strip_classes”NŒ report_level”KŒ halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ traceback”ˆŒinput_encoding”Œ utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”jÞŒerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œ language_code”Œen”Œrecord_dependencies”NŒconfig”NŒ id_prefix”hŒauto_id_prefix”Œid”Œ dump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h¶Œ _destination”NŒ _config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒ raw_enabled”KŒline_length_limit”M'Œpep_references”NŒ pep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒ rfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œ smart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œ docinfo_xform”KŒsectsubtitle_xform”‰Œ image_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j¸jµj j jbj_jÉjÆjjjMjJj´j±j÷jôjjjEjBj´j±jÛjØjj jEjBjljij{jxjøjõjsjpj°j­uŒ nametypes”}”(j¸‰j ‰jb‰jɉj‰jM‰j´‰j÷‰j‰jE‰j´‰jÛ‰j‰jE‰jl‰j{‰jø‰js‰j°‰uh}”(jµh£j hÕj_jjÆjejjÌjJjj±jJjôj·jjújBj!j±jPjØj·j jÞjBjjijHjxjojõjœjpjûj­j~uŒ footnote_refs”}”Œ citation_refs”}”Œ autofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ footnotes”]”Œ citations”]”Œautofootnote_start”KŒsymbol_footnote_start”KŒ id_counter”Œ collections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œ transformer”NŒ include_log”]”Œ decoration”Nhžhub.