Re: [PATCH v6 8/9] dt-bindings: mux-adg792a: document devicetree bindings for ADG792A/G mux
From: Jonathan Cameron <jic23@kernel.org>
Date: 2017-01-01 11:00:38
Also in:
linux-i2c, linux-iio, lkml
On 30/11/16 08:17, Peter Rosin wrote:
Analog Devices ADG792A/G is a triple 4:1 mux. Signed-off-by: Peter Rosin <redacted>
Few comments inline. Worth adding anything about the gpio (output pins) to the binding at this stage as well? Would certainly be nice to support them. Jonathan
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--- .../devicetree/bindings/misc/mux-adg792a.txt | 64 ++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 Documentation/devicetree/bindings/misc/mux-adg792a.txtdiff --git a/Documentation/devicetree/bindings/misc/mux-adg792a.txt b/Documentation/devicetree/bindings/misc/mux-adg792a.txt new file mode 100644 index 000000000000..4677f9ab1c55 --- /dev/null +++ b/Documentation/devicetree/bindings/misc/mux-adg792a.txt@@ -0,0 +1,64 @@ +Bindings for Analog Devices ADG792A/G Triple 4:1 Multiplexers + +Required properties: +- compatible : "adi,adg792a" or "adi,adg792g" +- #mux-control-cells : <0> if parallel, or <1> if not. +* Standard mux-controller bindings as decribed in mux-controller.txt + +Optional properties: +- adi,parallel : if present, the three muxes are bound together with a single + mux controller, controlling all three muxes in parallel. +- adi,idle-state : if present, array of states the three mux controllers will + have when idle (or, if parallel, a single idle-state).
Hmm. These are actually a policy decision. As only one policy will make sense for a given set of hardware probably fine to have it in here I guess. Might be worth adding a note to say this though.
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+ +Mux controller states 0 through 3 correspond to signals A through D in the +datasheet. Mux controller states 4 and 5 are only available as possible idle +states. State 4 represents that nothing is connected, and state 5 represents +that the mux controller keeps the mux in its previously selected state during +the idle period. State 5 is the default idle state.
I'm never a great fan of magic numbers. Can we represent this more cleanly by breaking it into multiple properties? Optional: adi,idle-switch-to-channel : switch to this channel when idle. adi,idle-high-impedance : <boolean> the nothing connected state? If neither present leaves it in previous state?
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+ +Example: + + /* three independent mux controllers (of which one is used) */ + &i2c0 { + mux: adg792a@50 { + compatible = "adi,adg792a"; + reg = <0x50>; + #mux-control-cells = <1>; + }; + }; + + adc-mux { + compatible = "iio-mux"; + io-channels = <&adc 0>; + io-channel-names = "parent"; + + mux-controls = <&mux 1>; + + channels = "sync-1", "", "out"; + }; + + + /* + * Three parallel muxes with one mux controller, useful e.g. if + * the adc is differential, thus needing two signals to be muxed + * simultaneously for correct operation. + */ + &i2c0 { + pmux: adg792a@50 { + compatible = "adi,adg792a"; + reg = <0x50>; + #mux-control-cells = <0>; + adi,parallel; + }; + }; + + diff-adc-mux { + compatible = "iio-mux"; + io-channels = <&adc 0>; + io-channel-names = "parent"; + + mux-controls = <&pmux>; + + channels = "sync-1", "", "out"; + };