linux-kernel - Re: [PATCH 0/2] mux: gpio: add support for ADG1712 quad SPST switch

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Message-ID: <f81e216a-7af0-4779-afb5-3a82f4711cd5@baylibre.com>
Date: Fri, 21 Nov 2025 08:30:40 -0600
From: David Lechner <dlechner@...libre.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>,
 Peter Rosin <peda@...ntia.se>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Linus Walleij <linus.walleij@...aro.org>,
 Bartosz Golaszewski <brgl@...ev.pl>, Srinivas Kandagatla <srini@...nel.org>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-gpio@...r.kernel.org
Subject: Re: [PATCH 0/2] mux: gpio: add support for ADG1712 quad SPST switch

On 11/21/25 5:57 AM, Antoniu Miclaus wrote:
> This series adds support for the Analog Devices ADG1712 quad single-pole/
> single-throw (SPST) switch to the existing GPIO multiplexer driver.
> 
> The ADG1712 contains four independent switches, each controlled by a
> dedicated GPIO pin. Unlike traditional multiplexers that use GPIOs as
> binary-encoded selectors, the ADG1712 treats each GPIO as a direct switch
> controller.
> 
> However, the existing gpio-mux driver architecture handles this perfectly
> by treating the mux state (0-15) as representing all possible combinations
> of the four independent switches. The existing mux_gpio_set() function uses
> gpiod_multi_set_value_cansleep() which treats the state as a bitmap,
> setting each GPIO according to the corresponding bit position.
> 
> For example:
> - State 0 (0000): All switches OFF
> - State 5 (0101): SW1=ON, SW2=OFF, SW3=ON, SW4=OFF
> - State 15 (1111): All switches ON
> 
> This approach allows the ADG1712 to leverage the existing mux framework
> for switch control while reusing all existing gpio-mux infrastructure
> without any code changes beyond adding the compatible string.
> 

This doesn't sound like a mux at all. It sounds like a solid state
relay.

So it probably doesn't need bindings or a driver. You can just use
the gpio that controls it directly since the output will always
follow the gpio state. (And if the 65 ns delay is an issue, there
is "gpio-delay".)

Using a gpiod array gives the same convenience of being able to
use a value 0-15 to control the state of all 4 at the same time if
needed.