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34 .Nd driver for LTC4305 and LTC4306 I2C mux chips
36 To compile this driver into the kernel,
37 place the following line in your
38 kernel configuration file:
39 .Bd -ragged -offset indent
43 Alternatively, to load the driver as a
44 module at boot time, place the following line in
46 .Bd -literal -offset indent
52 driver supports the LTC4305 and LTC4306 I2C bus multiplexer (mux) chips.
53 It automatically connects an upstream I2C bus to one of several downstream
54 buses as needed when slave devices on the downstream buses initiate I/O.
55 More information on the automatic switching behavior is available in
62 device node is defined as a child node of its upstream i2c bus.
65 node are additional i2c buses, which will have their own i2c slave
66 devices described in their child nodes.
70 driver conforms to the standard
72 .Li i2c/i2c-mux-ltc4306.txt
74 bindings document, except that the following optional properties
75 are not currently supported and will be ignored if present:
76 .Bl -bullet -compact -inset -offset indent
84 ltc,downstream-accelerators-enable
86 ltc,upstream-accelerators-enable
89 In addition, the following additional property is supported:
90 .Bl -tag -offset indent -width indent
91 .It Va freebsd,ctlreg2
92 A value to store into the chip's control register 2 during initialization.
93 Consult the chip datasheet for the meaning of the various bits in
96 .Sh HINTS CONFIGURATION
99 based system, the following hints are required:
100 .Bl -tag -offset indent -width indent
101 .It Va hint.ltc430x.<unit>.at
106 instance is attached to.
107 .It Va hint.ltc430x.<unit>.addr
108 The slave address of the
110 instance on the upstream bus.
111 .It Va hint.ltc430x.<unit>.chip_type
112 The type of chip the driver is controlling.
119 The following hints are optional:
120 .Bl -tag -offset indent -width indent
121 .It Va hint.ltc430x.<unit>.ctlreg2
122 A value to store into the chip's control register 2 during initialization.
123 Consult the chip datasheet for the meaning of the various bits in
125 This hint is optional; when missing, the driver does not update control
127 .It Va hint.ltc430x.<unit>.idle_disconnect
128 Whether to disconnect all downstream busses from the upstream bus when idle.
129 If set to zero, the most recently used downstream bus is left connected to
130 the upstream bus after IO completes.
131 Any non-zero value causes all downstream busses to be disconnected when idle.
132 This hint is optional; when missing, the driver behaves as if it were zero.
135 When configured via hints, the driver automatically adds an iicbus
136 instance for every downstream bus supported by the chip.
137 There is currently no way to indicate used versus unused downstream channels.
144 driver first appeared in