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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:55 EST.

1	Generic device tree bindings for I2C busses
2	===========================================
3	
4	This document describes generic bindings which can be used to describe I2C
5	busses in a device tree.
6	
7	Required properties
8	-------------------
9	
10	- #address-cells  - should be <1>. Read more about addresses below.
11	- #size-cells     - should be <0>.
12	- compatible      - name of I2C bus controller following generic names
13			    recommended practice.
14	
15	For other required properties e.g. to describe register sets,
16	clocks, etc. check the binding documentation of the specific driver.
17	
18	The cells properties above define that an address of children of an I2C bus
19	are described by a single value. This is usually a 7 bit address. However,
20	flags can be attached to the address. I2C_TEN_BIT_ADDRESS is used to mark a 10
21	bit address. It is needed to avoid the ambiguity between e.g. a 7 bit address
22	of 0x50 and a 10 bit address of 0x050 which, in theory, can be on the same bus.
23	Another flag is I2C_OWN_SLAVE_ADDRESS to mark addresses on which we listen to
24	be devices ourselves.
25	
26	Optional properties
27	-------------------
28	
29	These properties may not be supported by all drivers. However, if a driver
30	wants to support one of the below features, it should adapt the bindings below.
31	
32	- clock-frequency
33		frequency of bus clock in Hz.
34	
35	- i2c-bus
36		For I2C adapters that have child nodes that are a mixture of both I2C
37		devices and non-I2C devices, the 'i2c-bus' subnode can be used for
38		populating I2C devices. If the 'i2c-bus' subnode is present, only
39		subnodes of this will be considered as I2C slaves. The properties,
40		'#address-cells' and '#size-cells' must be defined under this subnode
41		if present.
42	
43	- i2c-scl-falling-time-ns
44		Number of nanoseconds the SCL signal takes to fall; t(f) in the I2C
45		specification.
46	
47	- i2c-scl-internal-delay-ns
48		Number of nanoseconds the IP core additionally needs to setup SCL.
49	
50	- i2c-scl-rising-time-ns
51		Number of nanoseconds the SCL signal takes to rise; t(r) in the I2C
52		specification.
53	
54	- i2c-sda-falling-time-ns
55		Number of nanoseconds the SDA signal takes to fall; t(f) in the I2C
56		specification.
57	
58	- interrupts
59		interrupts used by the device.
60	
61	- interrupt-names
62		"irq" and "wakeup" names are recognized by I2C core, other names are
63		left to individual drivers.
64	
65	- host-notify
66		device uses SMBus host notify protocol instead of interrupt line.
67	
68	- multi-master
69		states that there is another master active on this bus. The OS can use
70		this information to adapt power management to keep the arbitration awake
71		all the time, for example.
72	
73	- wakeup-source
74		device can be used as a wakeup source.
75	
76	- reg
77		I2C slave addresses
78	
79	- reg-names
80		Names of map programmable addresses.
81		It can contain any map needing another address than default one.
82	
83	Binding may contain optional "interrupts" property, describing interrupts
84	used by the device. I2C core will assign "irq" interrupt (or the very first
85	interrupt if not using interrupt names) as primary interrupt for the slave.
86	
87	Alternatively, devices supporting SMbus Host Notify, and connected to
88	adapters that support this feature, may use "host-notify" property. I2C
89	core will create a virtual interrupt for Host Notify and assign it as
90	primary interrupt for the slave.
91	
92	Also, if device is marked as a wakeup source, I2C core will set up "wakeup"
93	interrupt for the device. If "wakeup" interrupt name is not present in the
94	binding, then primary interrupt will be used as wakeup interrupt.
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