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2 .\" SPDX-License-Identifier: BSD-2-Clause
32 .Nd I2C bus mulitiplexer framework
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55 I2C bus multiplexer (mux) hardware.
64 Generally speaking, an I2C mux is connected to an upstream I2C bus, and to
66 any one of the downstream buses to the upstream bus.
75 the active downstream bus.
84 downstream bus (if any) should be connected while in the idle state.
85 In the absence of such configuration, whichever downstream bus was
86 last used remains connected to the upstream bus.
88 When an I2C slave device on a bus downstream of a mux initiates I/O,
89 it first requests exclusive use of the bus by calling
91 This request is communicated to the bus's parent, which is the
95 Once exclusive bus ownership is obtained, the mux driver
96 connects the upstream I2C bus to the downstream bus which hosts the
97 slave device that requested bus ownership.
98 The mux hardware maintains that upstream-to-downstream connection until
106 based system, an I2C mux device node is defined as a child node of its
107 upstream I2C bus when the mux device is an I2C slave itself.
108 It may be defined as a child node of any other bus or device in the
109 system when it is not an I2C slave, in which case the
110 .Va i2c-parent
111 property indicates which upstream bus the mux is attached to.
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119 .Li i2c/i2c-mux.txt
125 based system, these values are configurable for
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138 instance for every downstream bus supported by the chip.