Documentation/i2c/i2c-sysfs.rst

12 kernel abstracts the MUX channels into logical I2C bus numbers. However, there
14 to logical I2C bus number. This doc is aimed to fill in this gap, so the
16 the concept of logical I2C buses in the kernel, by knowing the physical I2C
41 start with ``i2c-`` are I2C buses, which may be either physical or logical. The
77 Logical I2C Bus
80 Every I2C bus number you see in Linux I2C Sysfs is a logical I2C bus with a
84 Each logical I2C bus may be an abstraction of a physical I2C bus controller, or
86 MUX channel, whenever we access an I2C device via a such logical bus, the kernel
93 If the logical I2C bus is a direct abstraction of a physical I2C bus controller,
101 to a different number in logical I2C bus level in Device Tree Source (DTS) under
106 bus physical number the same as their corresponding logical I2C bus number,
112 Walk through Logical I2C Bus
135 Distinguish Physical and Logical I2C Bus
138 One simple way to distinguish between a physical I2C bus and a logical I2C bus,
143 in logical I2C bus directory which is fanned out from another I2C bus.
145 this logical I2C bus.
162 presented by the current directory has to be a logical bus. The I2C bus pointed
164 logical one. In this case, the I2C bus presented by the current directory
174 ``i2c-73`` is a logical bus fanout by an I2C MUX under ``i2c-7``
180 Finding out Logical I2C Bus Number
183 In this section, we will describe how to find out the logical I2C bus number
190 navigate through Sysfs and find out the logical I2C bus number of the channel 3
216 with a logical I2C bus number of 73.
232 we can now find the 0x72 MUX and what logical I2C bus numbers
251 There, we find out the logical I2C bus number of the channel 3 of the 0x72 MUX
277 Pinned Logical I2C Bus Number
281 successfully probed, the kernel will assign the MUX channels with a logical bus
282 number based on the current biggest logical bus number incrementally. For
283 example, if the system has ``i2c-15`` as the highest logical bus number, and a
288 logical I2C bus number in the DTS. This doc will not go through the details on
294 and pinned to logical I2C bus number 18 with the line of ``i2c18 = &imux18;``
297 Take it further, it is possible to design a logical I2C bus number schema that
300 logical bus number of the channel 0 of the MUX on bus 3, and 37 will be the
301 logical bus number of the channel 7 of the MUX on bus 3.
308 of ``${bus}-${addr}``. The ``${bus}`` part in the name is a logical I2C bus
352 These symbolic links point to their logical I2C bus directories::