* [PATCH v7 1/2] dt-bindings: gpio: add gpio-line-mux controller
2025-12-27 18:01 [PATCH v7 0/2] add gpio-line-mux Jonas Jelonek
@ 2025-12-27 18:01 ` Jonas Jelonek
2025-12-27 18:01 ` [PATCH v7 2/2] gpio: add gpio-line-mux driver Jonas Jelonek
` (2 subsequent siblings)
3 siblings, 0 replies; 7+ messages in thread
From: Jonas Jelonek @ 2025-12-27 18:01 UTC (permalink / raw)
To: Linus Walleij, Bartosz Golaszewski, Rob Herring,
Krzysztof Kozlowski, Conor Dooley, Peter Rosin,
Geert Uytterhoeven
Cc: linux-gpio, devicetree, linux-kernel, Thomas Richard,
Jonas Jelonek, Conor Dooley
Add dt-schema for a gpio-line-mux controller which exposes virtual
GPIOs for a shared GPIO controlled by a multiplexer, e.g. a gpio-mux.
The gpio-line-mux controller is a gpio-controller, thus has mostly the
same semantics. However, it requires a mux-control to be specified upon
which it will operate.
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
.../bindings/gpio/gpio-line-mux.yaml | 107 ++++++++++++++++++
1 file changed, 107 insertions(+)
create mode 100644 Documentation/devicetree/bindings/gpio/gpio-line-mux.yaml
diff --git a/Documentation/devicetree/bindings/gpio/gpio-line-mux.yaml b/Documentation/devicetree/bindings/gpio/gpio-line-mux.yaml
new file mode 100644
index 000000000000..f49c05249ca7
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-line-mux.yaml
@@ -0,0 +1,107 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/gpio-line-mux.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: GPIO line mux
+
+maintainers:
+ - Jonas Jelonek <jelonek.jonas@gmail.com>
+
+description: |
+ A GPIO controller to provide virtual GPIOs for a 1-to-many input-only mapping
+ backed by a single shared GPIO and a multiplexer. A simple illustrated
+ example is:
+
+ +----- A
+ IN /
+ <-----o------- B
+ / |\
+ | | +----- C
+ | | \
+ | | +--- D
+ | |
+ M1 M0
+
+ MUX CONTROL
+
+ M1 M0 IN
+ 0 0 A
+ 0 1 B
+ 1 0 C
+ 1 1 D
+
+ This can be used in case a real GPIO is connected to multiple inputs and
+ controlled by a multiplexer, and another subsystem/driver does not work
+ directly with the multiplexer subsystem.
+
+properties:
+ compatible:
+ const: gpio-line-mux
+
+ gpio-controller: true
+
+ "#gpio-cells":
+ const: 2
+
+ gpio-line-mux-states:
+ description: Mux states corresponding to the virtual GPIOs.
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+
+ gpio-line-names: true
+
+ mux-controls:
+ maxItems: 1
+ description:
+ Phandle to the multiplexer to control access to the GPIOs.
+
+ ngpios: false
+
+ muxed-gpios:
+ maxItems: 1
+ description:
+ GPIO which is the '1' in 1-to-many and is shared by the virtual GPIOs
+ and controlled via the mux.
+
+required:
+ - compatible
+ - gpio-controller
+ - gpio-line-mux-states
+ - mux-controls
+ - muxed-gpios
+
+additionalProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/gpio/gpio.h>
+ #include <dt-bindings/mux/mux.h>
+
+ sfp_gpio_mux: mux-controller-1 {
+ compatible = "gpio-mux";
+ mux-gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>,
+ <&gpio0 1 GPIO_ACTIVE_HIGH>;
+ #mux-control-cells = <0>;
+ idle-state = <MUX_IDLE_AS_IS>;
+ };
+
+ sfp1_gpio: sfp-gpio-1 {
+ compatible = "gpio-line-mux";
+ gpio-controller;
+ #gpio-cells = <2>;
+
+ mux-controls = <&sfp_gpio_mux>;
+ muxed-gpios = <&gpio0 2 GPIO_ACTIVE_HIGH>;
+
+ gpio-line-mux-states = <0>, <1>, <3>;
+ };
+
+ sfp1: sfp-p1 {
+ compatible = "sff,sfp";
+
+ i2c-bus = <&sfp1_i2c>;
+ los-gpios = <&sfp1_gpio 0 GPIO_ACTIVE_HIGH>;
+ mod-def0-gpios = <&sfp1_gpio 1 GPIO_ACTIVE_LOW>;
+ tx-fault-gpios = <&sfp1_gpio 2 GPIO_ACTIVE_HIGH>;
+ };
--
2.48.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH v7 2/2] gpio: add gpio-line-mux driver
2025-12-27 18:01 [PATCH v7 0/2] add gpio-line-mux Jonas Jelonek
2025-12-27 18:01 ` [PATCH v7 1/2] dt-bindings: gpio: add gpio-line-mux controller Jonas Jelonek
@ 2025-12-27 18:01 ` Jonas Jelonek
2026-01-07 8:40 ` Dan Carpenter
2026-01-02 10:10 ` [PATCH v7 0/2] add gpio-line-mux Bartosz Golaszewski
2026-01-04 12:11 ` Linus Walleij
3 siblings, 1 reply; 7+ messages in thread
From: Jonas Jelonek @ 2025-12-27 18:01 UTC (permalink / raw)
To: Linus Walleij, Bartosz Golaszewski, Rob Herring,
Krzysztof Kozlowski, Conor Dooley, Peter Rosin,
Geert Uytterhoeven
Cc: linux-gpio, devicetree, linux-kernel, Thomas Richard,
Jonas Jelonek
Add a new driver which provides a 1-to-many mapping for a single real
GPIO using a multiplexer. Each virtual GPIO corresponds to a multiplexer
state which, if set for the multiplexer, connects the real GPIO to the
corresponding virtual GPIO.
This can help in various usecases. One practical case is the special
hardware design of the Realtek-based XS1930-10 switch from Zyxel. It
features two SFP+ ports/cages whose signals are wired directly to the
switch SoC. Although Realtek SoCs are short on GPIOs, there are usually
enough the fit the SFP signals without any hacks.
However, Zyxel did some weird design and connected RX_LOS, MOD_ABS and
TX_FAULT of one SFP cage onto a single GPIO line controlled by a
multiplexer (the same for the other SFP cage). The single multiplexer
controls the lines for both SFP and depending on the state, the
designated 'signal GPIO lines' are connected to one of the three SFP
signals.
Because the SFP core/driver doesn't support multiplexer but needs single
GPIOs for each of the signals, this driver fills the gap between both.
It registers a gpio_chip, provides multiple virtual GPIOs and sets the
backing multiplexer accordingly.
Due to several practical issues, this is input-only and doesn't support
IRQs.
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Reviewed-by: Thomas Richard <thomas.richard@bootlin.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
MAINTAINERS | 6 ++
drivers/gpio/Kconfig | 9 +++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-line-mux.c | 126 +++++++++++++++++++++++++++++++++++
4 files changed, 142 insertions(+)
create mode 100644 drivers/gpio/gpio-line-mux.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 5b11839cba9d..8056ef0ffbf0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10774,6 +10774,12 @@ S: Maintained
F: Documentation/devicetree/bindings/leds/irled/gpio-ir-tx.yaml
F: drivers/media/rc/gpio-ir-tx.c
+GPIO LINE MUX
+M: Jonas Jelonek <jelonek.jonas@gmail.com>
+S: Maintained
+F: Documentation/devicetree/bindings/gpio/gpio-line-mux.yaml
+F: drivers/gpio/gpio-line-mux.c
+
GPIO MOCKUP DRIVER
M: Bamvor Jian Zhang <bamv2005@gmail.com>
L: linux-gpio@vger.kernel.org
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index c33f9305ab97..2efa58f10781 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1994,6 +1994,15 @@ config GPIO_LATCH
Say yes here to enable a driver for GPIO multiplexers based on latches
connected to other GPIOs.
+config GPIO_LINE_MUX
+ tristate "GPIO line mux driver"
+ depends on OF_GPIO
+ select MULTIPLEXER
+ help
+ Say Y here to support the GPIO line mux, which can provide virtual
+ GPIOs backed by a shared real GPIO and a multiplexer in a 1-to-many
+ fashion.
+
config GPIO_MOCKUP
tristate "GPIO Testing Driver (DEPRECATED)"
select IRQ_SIM
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 2421a8fd3733..36fa7c52d240 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -90,6 +90,7 @@ obj-$(CONFIG_GPIO_IXP4XX) += gpio-ixp4xx.o
obj-$(CONFIG_GPIO_JANZ_TTL) += gpio-janz-ttl.o
obj-$(CONFIG_GPIO_KEMPLD) += gpio-kempld.o
obj-$(CONFIG_GPIO_LATCH) += gpio-latch.o
+obj-$(CONFIG_GPIO_LINE_MUX) += gpio-line-mux.o
obj-$(CONFIG_GPIO_LJCA) += gpio-ljca.o
obj-$(CONFIG_GPIO_LOGICVC) += gpio-logicvc.o
obj-$(CONFIG_GPIO_LOONGSON1) += gpio-loongson1.o
diff --git a/drivers/gpio/gpio-line-mux.c b/drivers/gpio/gpio-line-mux.c
new file mode 100644
index 000000000000..a4f384306218
--- /dev/null
+++ b/drivers/gpio/gpio-line-mux.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GPIO line mux which acts as virtual gpiochip and provides a 1-to-many
+ * mapping between virtual GPIOs and a real GPIO + multiplexer.
+ *
+ * Copyright (c) 2025 Jonas Jelonek <jelonek.jonas@gmail.com>
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/mod_devicetable.h>
+#include <linux/mutex.h>
+#include <linux/mux/consumer.h>
+#include <linux/platform_device.h>
+
+#define MUX_SELECT_DELAY_US 100
+
+struct gpio_lmux {
+ struct gpio_chip gc;
+ struct mux_control *mux;
+ struct gpio_desc *muxed_gpio;
+
+ u32 num_gpio_mux_states;
+ unsigned int gpio_mux_states[] __counted_by(num_gpio_mux_states);
+};
+
+static int gpio_lmux_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+ struct gpio_lmux *glm = gpiochip_get_data(gc);
+ int ret;
+
+ if (offset > gc->ngpio)
+ return -EINVAL;
+
+ ret = mux_control_select_delay(glm->mux, glm->gpio_mux_states[offset],
+ MUX_SELECT_DELAY_US);
+ if (ret < 0)
+ return ret;
+
+ ret = gpiod_get_raw_value_cansleep(glm->muxed_gpio);
+ mux_control_deselect(glm->mux);
+ return ret;
+}
+
+static int gpio_lmux_gpio_set(struct gpio_chip *gc, unsigned int offset,
+ int value)
+{
+ return -EOPNOTSUPP;
+}
+
+static int gpio_lmux_gpio_get_direction(struct gpio_chip *gc,
+ unsigned int offset)
+{
+ return GPIO_LINE_DIRECTION_IN;
+}
+
+static int gpio_lmux_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct gpio_lmux *glm;
+ unsigned int ngpio;
+ size_t size;
+ int ret;
+
+ ngpio = device_property_count_u32(dev, "gpio-line-mux-states");
+ if (!ngpio)
+ return -EINVAL;
+
+ size = struct_size(glm, gpio_mux_states, ngpio);
+ glm = devm_kzalloc(dev, size, GFP_KERNEL);
+ if (!glm)
+ return -ENOMEM;
+
+ glm->gc.base = -1;
+ glm->gc.can_sleep = true;
+ glm->gc.fwnode = dev_fwnode(dev);
+ glm->gc.label = dev_name(dev);
+ glm->gc.ngpio = ngpio;
+ glm->gc.owner = THIS_MODULE;
+ glm->gc.parent = dev;
+
+ glm->gc.get = gpio_lmux_gpio_get;
+ glm->gc.set = gpio_lmux_gpio_set;
+ glm->gc.get_direction = gpio_lmux_gpio_get_direction;
+
+ glm->mux = devm_mux_control_get(dev, NULL);
+ if (IS_ERR(glm->mux))
+ return dev_err_probe(dev, PTR_ERR(glm->mux),
+ "could not get mux controller\n");
+
+ glm->muxed_gpio = devm_gpiod_get(dev, "muxed", GPIOD_IN);
+ if (IS_ERR(glm->muxed_gpio))
+ return dev_err_probe(dev, PTR_ERR(glm->muxed_gpio),
+ "could not get muxed-gpio\n");
+
+ glm->num_gpio_mux_states = ngpio;
+ ret = device_property_read_u32_array(dev, "gpio-line-mux-states",
+ &glm->gpio_mux_states[0], ngpio);
+ if (ret)
+ return dev_err_probe(dev, ret, "could not get mux states\n");
+
+ ret = devm_gpiochip_add_data(dev, &glm->gc, glm);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to add gpiochip\n");
+
+ return 0;
+}
+
+static const struct of_device_id gpio_lmux_of_match[] = {
+ { .compatible = "gpio-line-mux" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, gpio_lmux_of_match);
+
+static struct platform_driver gpio_lmux_driver = {
+ .driver = {
+ .name = "gpio-line-mux",
+ .of_match_table = gpio_lmux_of_match,
+ },
+ .probe = gpio_lmux_probe,
+};
+module_platform_driver(gpio_lmux_driver);
+
+MODULE_AUTHOR("Jonas Jelonek <jelonek.jonas@gmail.com>");
+MODULE_DESCRIPTION("GPIO line mux driver");
+MODULE_LICENSE("GPL");
--
2.48.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH v7 2/2] gpio: add gpio-line-mux driver
2025-12-27 18:01 ` [PATCH v7 2/2] gpio: add gpio-line-mux driver Jonas Jelonek
@ 2026-01-07 8:40 ` Dan Carpenter
2026-01-07 8:52 ` Bartosz Golaszewski
0 siblings, 1 reply; 7+ messages in thread
From: Dan Carpenter @ 2026-01-07 8:40 UTC (permalink / raw)
To: Jonas Jelonek
Cc: Linus Walleij, Bartosz Golaszewski, Rob Herring,
Krzysztof Kozlowski, Conor Dooley, Peter Rosin,
Geert Uytterhoeven, linux-gpio, devicetree, linux-kernel,
Thomas Richard
On Sat, Dec 27, 2025 at 06:01:34PM +0000, Jonas Jelonek wrote:
> +struct gpio_lmux {
> + struct gpio_chip gc;
> + struct mux_control *mux;
> + struct gpio_desc *muxed_gpio;
> +
> + u32 num_gpio_mux_states;
> + unsigned int gpio_mux_states[] __counted_by(num_gpio_mux_states);
> +};
> +
> +static int gpio_lmux_gpio_get(struct gpio_chip *gc, unsigned int offset)
> +{
> + struct gpio_lmux *glm = gpiochip_get_data(gc);
> + int ret;
> +
> + if (offset > gc->ngpio)
This is off by one. Should be >=.
regards,
dan carpenter
> + return -EINVAL;
> +
> + ret = mux_control_select_delay(glm->mux, glm->gpio_mux_states[offset],
> + MUX_SELECT_DELAY_US);
> + if (ret < 0)
> + return ret;
> +
> + ret = gpiod_get_raw_value_cansleep(glm->muxed_gpio);
> + mux_control_deselect(glm->mux);
> + return ret;
> +}
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v7 2/2] gpio: add gpio-line-mux driver
2026-01-07 8:40 ` Dan Carpenter
@ 2026-01-07 8:52 ` Bartosz Golaszewski
0 siblings, 0 replies; 7+ messages in thread
From: Bartosz Golaszewski @ 2026-01-07 8:52 UTC (permalink / raw)
To: Dan Carpenter
Cc: Jonas Jelonek, Linus Walleij, Rob Herring, Krzysztof Kozlowski,
Conor Dooley, Peter Rosin, Geert Uytterhoeven, linux-gpio,
devicetree, linux-kernel, Thomas Richard
On Wed, Jan 7, 2026 at 9:40 AM Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> On Sat, Dec 27, 2025 at 06:01:34PM +0000, Jonas Jelonek wrote:
> > +struct gpio_lmux {
> > + struct gpio_chip gc;
> > + struct mux_control *mux;
> > + struct gpio_desc *muxed_gpio;
> > +
> > + u32 num_gpio_mux_states;
> > + unsigned int gpio_mux_states[] __counted_by(num_gpio_mux_states);
> > +};
> > +
> > +static int gpio_lmux_gpio_get(struct gpio_chip *gc, unsigned int offset)
> > +{
> > + struct gpio_lmux *glm = gpiochip_get_data(gc);
> > + int ret;
> > +
> > + if (offset > gc->ngpio)
>
> This is off by one. Should be >=.
>
And it's not even needed, GPIO core handles it. I'll send a patch to remove it.
Bart
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v7 0/2] add gpio-line-mux
2025-12-27 18:01 [PATCH v7 0/2] add gpio-line-mux Jonas Jelonek
2025-12-27 18:01 ` [PATCH v7 1/2] dt-bindings: gpio: add gpio-line-mux controller Jonas Jelonek
2025-12-27 18:01 ` [PATCH v7 2/2] gpio: add gpio-line-mux driver Jonas Jelonek
@ 2026-01-02 10:10 ` Bartosz Golaszewski
2026-01-04 12:11 ` Linus Walleij
3 siblings, 0 replies; 7+ messages in thread
From: Bartosz Golaszewski @ 2026-01-02 10:10 UTC (permalink / raw)
To: Linus Walleij, Bartosz Golaszewski, Rob Herring,
Krzysztof Kozlowski, Conor Dooley, Peter Rosin,
Geert Uytterhoeven, Jonas Jelonek
Cc: Bartosz Golaszewski, linux-gpio, devicetree, linux-kernel,
Thomas Richard
On Sat, 27 Dec 2025 18:01:32 +0000, Jonas Jelonek wrote:
> This proposes a new type of virtual GPIO controller and corresponding
> driver to provide a 1-to-many mapping between virtual GPIOs and a single
> real GPIO in combination with a multiplexer. Existing drivers apparently
> do not serve the purpose for what I need.
>
> I came across an issue with a switch device from Zyxel which has two
> SFP+ cages. Most similar switches either wire up the SFP signals
> (RX_LOS, MOD_ABS, TX_FAULT, TX_DISABLE) directly to the SoC (if it has
> enough GPIOs) or two a GPIO expander (for which a driver usually
> exists). However, Zyxel decided to do it differently in the following
> way:
> The signals RX_LOS, MOD_ABS and TX_FAULT share a single GPIO line to
> the SoC. Which one is actually connected to that GPIO line at a time
> is controlled by a separate multiplexer, a GPIO multiplexer in this
> case (which uses two other GPIOs). Only the TX_DISABLE is separate.
>
> [...]
Applied, thanks!
[1/2] dt-bindings: gpio: add gpio-line-mux controller
commit: 2a7618ba8698874e9871a8ec5453e0068e94d9e5
[2/2] gpio: add gpio-line-mux driver
commit: 2b03d9a40cd1fea42fd65d2b66df80edc0f374c8
Best regards,
--
Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v7 0/2] add gpio-line-mux
2025-12-27 18:01 [PATCH v7 0/2] add gpio-line-mux Jonas Jelonek
` (2 preceding siblings ...)
2026-01-02 10:10 ` [PATCH v7 0/2] add gpio-line-mux Bartosz Golaszewski
@ 2026-01-04 12:11 ` Linus Walleij
3 siblings, 0 replies; 7+ messages in thread
From: Linus Walleij @ 2026-01-04 12:11 UTC (permalink / raw)
To: Jonas Jelonek
Cc: Linus Walleij, Bartosz Golaszewski, Rob Herring,
Krzysztof Kozlowski, Conor Dooley, Peter Rosin,
Geert Uytterhoeven, linux-gpio, devicetree, linux-kernel,
Thomas Richard
On Sat, Dec 27, 2025 at 7:01 PM Jonas Jelonek <jelonek.jonas@gmail.com> wrote:
> This proposes a new type of virtual GPIO controller and corresponding
> driver to provide a 1-to-many mapping between virtual GPIOs and a single
> real GPIO in combination with a multiplexer. Existing drivers apparently
> do not serve the purpose for what I need.
Thanks for persisting and doing this the right way all the way through,
Jonas!
This driver will probably be helpful for other users with the same
quirk in the future.
Yours,
Linus Walleij
^ permalink raw reply [flat|nested] 7+ messages in thread