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Date: Fri, 27 Jan 2017 11:49:19 -0600
From: Rob Herring <robh@...nel.org>
To: Peter Rosin <peda@...ntia.se>
Cc: linux-kernel@...r.kernel.org, Wolfram Sang <wsa@...-dreams.de>,
Mark Rutland <mark.rutland@....com>,
Jonathan Cameron <jic23@...nel.org>,
Hartmut Knaack <knaack.h@....de>,
Lars-Peter Clausen <lars@...afoo.de>,
Peter Meerwald-Stadler <pmeerw@...erw.net>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
linux-iio@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v8 02/12] dt-bindings: document devicetree bindings for
mux-controllers and mux-gpio
On Wed, Jan 18, 2017 at 04:57:05PM +0100, Peter Rosin wrote:
> Allow specifying that a single multiplexer controller can be used to control
> several parallel multiplexers, thus enabling sharing of the multiplexer
> controller by different consumers.
>
> Add a binding for a first mux controller in the form of a GPIO based mux
> controlled.
>
> Acked-by: Jonathan Cameron <jic23@...nel.org>
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
> .../devicetree/bindings/mux/mux-controller.txt | 127 +++++++++++++++++++++
> Documentation/devicetree/bindings/mux/mux-gpio.txt | 68 +++++++++++
> MAINTAINERS | 5 +
> 3 files changed, 200 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/mux/mux-controller.txt
> create mode 100644 Documentation/devicetree/bindings/mux/mux-gpio.txt
A few nits. With those fixed:
Acked-by: Rob Herring <robh@...nel.org>
>
> diff --git a/Documentation/devicetree/bindings/mux/mux-controller.txt b/Documentation/devicetree/bindings/mux/mux-controller.txt
> new file mode 100644
> index 000000000000..42b2177e5ae1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mux/mux-controller.txt
> @@ -0,0 +1,127 @@
> +Common multiplexer controller bindings
> +======================================
> +
> +A multiplexer (or mux) controller will have one, or several, consumer devices
> +that uses the mux controller. Thus, a mux controller can possibly control
> +several parallel multiplexers. Presumably there will be at least one
> +multiplexer needed by each consumer, but a single mux controller can of course
> +control several multiplexers for a single consumer.
> +
> +A mux controller provides a number of states to its consumers, and the state
> +space is a simple zero-based enumeration. I.e. 0-1 for a 2-way multiplexer,
> +0-7 for an 8-way multiplexer, etc.
> +
> +
> +Consumers
> +---------
> +
> +Mux controller consumers should specify a list of mux controllers that they
> +want to use with a property containing a 'mux-ctrl-list':
> +
> + mux-ctrl-list ::= <single-mux-ctrl> [mux-ctrl-list]
> + single-mux-ctrl ::= <mux-ctrl-phandle> [mux-ctrl-specifier]
> + mux-ctrl-phandle : phandle to mux controller node
> + mux-ctrl-specifier : array of #mux-control-cells specifying the
> + given mux controller (controller specific)
> +
> +Mux controller properties should be named "mux-controls". The exact meaning of
> +each mux controller property must be documented in the device tree binding for
> +each consumer. An optional property "mux-control-names" may contain a list of
> +strings to label each of the mux controllers listed in the "mux-controls"
> +property.
> +
> +Drivers for devices that use more than a single mux controller can use the
> +"mux-control-names" property to map the name of the requested mux controller
> +to an index into the list given by the "mux-controls" property.
> +
> +mux-ctrl-specifier typically encodes the chip-relative mux controller number.
> +If the mux controller chip only provides a single mux controller, the
> +mux-ctrl-specifier can typically be left out.
> +
> +Example:
> +
> + /* One consumer of a 2-way mux controller (one GPIO-line) */
> + mux: mux-controller {
> + compatible = "mux-gpio";
> + #mux-control-cells = <0>;
> +
> + mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>;
> + };
> +
> + adc-mux {
> + compatible = "io-channel-mux";
> + io-channels = <&adc 0>;
> + io-channel-names = "parent";
> + mux-controls = <&mux>;
> + mux-control-names = "adc";
> +
> + channels = "sync", "in";
> + };
> +
> +Note that in the example above, specifying the "mux-control-names" is redundant
> +because there is only one mux controller in the list.
> +
> + /*
> + * Two consumers (one for an ADC line and one for an i2c bus) of
> + * parallel 4-way multiplexers controlled by the same two GPIO-lines.
> + */
> + mux: mux-controller {
> + compatible = "mux-gpio";
> + #mux-control-cells = <0>;
> +
> + mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
> + <&pioA 1 GPIO_ACTIVE_HIGH>;
> + };
> +
> + adc-mux {
> + compatible = "io-channel-mux";
> + io-channels = <&adc 0>;
> + io-channel-names = "parent";
> + mux-controls = <&mux>;
> +
> + channels = "sync-1", "in", "out", "sync-2";
> + };
> +
> + i2c-mux {
> + compatible = "i2c-mux-simple,mux-locked";
> + i2c-parent = <&i2c1>;
> + mux-controls = <&mux>;
> +
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + i2c@0 {
> + reg = <0>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + ssd1307: oled@3c {
> + /* ... */
> + };
> + };
> +
> + i2c@3 {
> + reg = <3>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + pca9555: pca9555@20 {
> + /* ... */
> + };
> + };
> + };
> +
> +
> +Mux controller nodes
> +--------------------
> +
> +Mux controller nodes must specify the number of cells used for the
> +specifier using the '#mux-control-cells' property.
> +
> +An example mux controller might look like this:
> +
> + mux: adg792a@50 {
mux-controller@50
> + compatible = "adi,adg792a";
> + reg = <0x50>;
> + #mux-control-cells = <1>;
> + };
> diff --git a/Documentation/devicetree/bindings/mux/mux-gpio.txt b/Documentation/devicetree/bindings/mux/mux-gpio.txt
> new file mode 100644
> index 000000000000..8f6bda6f9d78
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mux/mux-gpio.txt
> @@ -0,0 +1,68 @@
> +GPIO-based multiplexer controller bindings
> +
> +Define what GPIO pins are used to control a multiplexer. Or several
> +multiplexers, if the same pins control more than one multiplexer.
> +
> +Required properties:
> +- compatible : "mux-gpio"
Just to be consistent with other gpio compatibles: gpio-mux
> +- mux-gpios : list of gpios used to control the multiplexer, least
> + significant bit first.
> +- #mux-control-cells : <0>
> +* Standard mux-controller bindings as decribed in mux-controller.txt
> +
> +Optional properties:
> +- idle-state : if present, the state the mux will have when idle.
Why is this gpio specific. Can be a common controller property?
> +
> +The multiplexer state is defined as the number represented by the
> +multiplexer GPIO pins, where the first pin is the least significant
> +bit. An active pin is a binary 1, an inactive pin is a binary 0.
> +
> +Example:
> +
> + mux: mux-controller {
> + compatible = "mux-gpio";
> + #mux-control-cells = <0>;
> +
> + mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
> + <&pioA 1 GPIO_ACTIVE_HIGH>;
> + };
> +
> + adc-mux {
> + compatible = "io-channel-mux";
> + io-channels = <&adc 0>;
> + io-channel-names = "parent";
> +
> + mux-controls = <&mux>;
> +
> + channels = "sync-1", "in", "out", "sync-2";
> + };
> +
> + i2c-mux {
> + compatible = "i2c-mux-simple,mux-locked";
> + i2c-parent = <&i2c1>;
> +
> + mux-controls = <&mux>;
> +
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + i2c@0 {
> + reg = <0>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + ssd1307: oled@3c {
> + /* ... */
> + };
> + };
> +
> + i2c@3 {
> + reg = <3>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + pca9555: pca9555@20 {
> + /* ... */
> + };
> + };
> + };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 40de344ba0e6..be57f5b8f2c2 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8469,6 +8469,11 @@ S: Orphan
> F: drivers/mmc/host/mmc_spi.c
> F: include/linux/spi/mmc_spi.h
>
> +MULTIPLEXER SUBSYSTEM
> +M: Peter Rosin <peda@...ntia.se>
> +S: Maintained
> +F: Documentation/devicetree/bindings/mux/
> +
> MULTISOUND SOUND DRIVER
> M: Andrew Veliath <andrewtv@....net>
> S: Maintained
> --
> 2.1.4
>
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