[PATCH 0/2] gpio: Add gpio-latch driver

[PATCH 0/2] gpio: Add gpio-latch driver

[Sascha Hauer]

This adds a gpio-driver which multiplexes existing GPIOs using latches.
Uwe asked [1] if that would be accectable as a new gpio driver, and here
is the result. For a better description what this is all about have a
look at the drawings in the patches.

The driver is pretty much straight forward. The only thing I wasn't sure
about is in which category in Kconfig the driver should be sorted in. I
decided for "Virtual GPIO drivers" which is not an exact match, but the
best I could find in the existing categories.

Sascha

[1] https://lore.kernel.org/all/CACRpkdaBO=JzokGUF6uXZc7ASVD7LjqBxTLGwX-FShM=A9gw9A@mail.gmail.com/t/

Sascha Hauer (2):
  gpio: Add gpio latch driver
  dt-bindings: gpio: Add gpio-latch binding document

 .../devicetree/bindings/gpio/gpio-latch.yaml  |  83 ++++++++
 drivers/gpio/Kconfig                          |   6 +
 drivers/gpio/Makefile                         |   1 +
 drivers/gpio/gpio-latch.c                     | 188 ++++++++++++++++++
 4 files changed, 278 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-latch.yaml
 create mode 100644 drivers/gpio/gpio-latch.c

-- 
2.30.2

[PATCH 1/2] gpio: Add gpio latch driver

[Sascha Hauer]

This driver implements a GPIO multiplexer based on latches connected to
other GPIOs. A set of data GPIOs is connected to the data input of
multiple latches. The clock input of each latch is driven by another
set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
are output only.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/gpio/Kconfig      |   6 ++
 drivers/gpio/Makefile     |   1 +
 drivers/gpio/gpio-latch.c | 188 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 195 insertions(+)
 create mode 100644 drivers/gpio/gpio-latch.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 0642f579196f2..e4603810ec910 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1690,6 +1690,12 @@ config GPIO_AGGREGATOR
 	      industrial control context, to be operated from userspace using
 	      the GPIO chardev interface.
 
+config GPIO_LATCH
+	tristate "GPIO latch driver"
+	help
+	  Say yes here to enable a driver for GPIO multiplexers based on latches
+	  connected to other GPIOs.
+
 config GPIO_MOCKUP
 	tristate "GPIO Testing Driver"
 	select IRQ_SIM
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index a0985d30f51bb..310fa08decc69 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -75,6 +75,7 @@ obj-$(CONFIG_GPIO_IT87)			+= gpio-it87.o
 obj-$(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_LOGICVC)		+= gpio-logicvc.o
 obj-$(CONFIG_GPIO_LOONGSON1)		+= gpio-loongson1.o
 obj-$(CONFIG_GPIO_LOONGSON)		+= gpio-loongson.o
diff --git a/drivers/gpio/gpio-latch.c b/drivers/gpio/gpio-latch.c
new file mode 100644
index 0000000000000..117fcadf76a51
--- /dev/null
+++ b/drivers/gpio/gpio-latch.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * GPIO latch driver
+ *
+ *  Copyright (C) 2022 Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * This driver implements a GPIO (or better GPO as there is no input)
+ * multiplexer based on latches like this:
+ *
+ * CLK0 ----------------------.        ,--------.
+ * CLK1 -------------------.  `--------|>    #0 |
+ *                         |           |        |
+ * OUT0 ----------------+--|-----------|D0    Q0|-----|<
+ * OUT1 --------------+-|--|-----------|D1    Q1|-----|<
+ * OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
+ * OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
+ * OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
+ * OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
+ * OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
+ * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
+ *        | | | | | | | |  |           `--------'
+ *        | | | | | | | |  |
+ *        | | | | | | | |  |           ,--------.
+ *        | | | | | | | |  `-----------|>    #1 |
+ *        | | | | | | | |              |        |
+ *        | | | | | | | `--------------|D0    Q0|-----|<
+ *        | | | | | | `----------------|D1    Q1|-----|<
+ *        | | | | | `------------------|D2    Q2|-----|<
+ *        | | | | `--------------------|D3    Q3|-----|<
+ *        | | | `----------------------|D4    Q4|-----|<
+ *        | | `------------------------|D5    Q5|-----|<
+ *        | `--------------------------|D6    Q6|-----|<
+ *        `----------------------------|D7    Q7|-----|<
+ *                                     `--------'
+ *
+ * The above is just an example. The actual number of number of latches and
+ * the number of inputs per latch is derived from the number of GPIOs given
+ * in the corresponding device tree properties.
+ */
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/gpio/driver.h>
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+
+#include "gpiolib.h"
+
+struct gpio_latch_priv {
+	struct gpio_chip gc;
+	struct gpio_descs *clk_gpios;
+	struct gpio_descs *data_gpios;
+	spinlock_t lock;
+	int n_ports;
+	int n_pins;
+	unsigned int *shadow;
+	struct mutex mutex;
+	spinlock_t spinlock;
+};
+
+static const struct of_device_id gpio_latch_ids[] = {
+	{
+		.compatible	= "gpio-latch",
+	}, {
+		/* sentinel */
+	}
+};
+MODULE_DEVICE_TABLE(of, gpio_latch_ids);
+
+static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static void __gpio_latch_set(struct gpio_latch_priv *priv, unsigned int offset, int val)
+{
+	int latch = offset / priv->n_pins;
+	int i;
+
+	if (val)
+		priv->shadow[latch] |= BIT(offset % priv->n_pins);
+	else
+		priv->shadow[latch] &= ~BIT(offset % priv->n_pins);
+
+	for (i = 0; i < priv->n_pins; i++)
+		gpiod_set_value(priv->data_gpios->desc[i], priv->shadow[latch] & BIT(i));
+
+	gpiod_set_value(priv->clk_gpios->desc[latch], 1);
+	gpiod_set_value(priv->clk_gpios->desc[latch], 0);
+}
+
+static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
+{
+	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->spinlock, flags);
+
+	__gpio_latch_set(priv, offset, val);
+
+	spin_unlock_irqrestore(&priv->spinlock, flags);
+}
+
+static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
+{
+	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
+
+	mutex_lock(&priv->mutex);
+
+	__gpio_latch_set(priv, offset, val);
+
+	mutex_unlock(&priv->mutex);
+}
+
+static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv)
+{
+	int i;
+
+	for (i = 0; i < priv->n_ports; i++)
+		if (gpiod_cansleep(priv->clk_gpios->desc[i]))
+			return true;
+
+	for (i = 0; i < priv->n_pins; i++)
+		if (gpiod_cansleep(priv->data_gpios->desc[i]))
+			return true;
+	
+	return false;
+}
+
+static int gpio_latch_probe(struct platform_device *pdev)
+{
+	struct gpio_latch_priv *priv;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->clk_gpios = devm_gpiod_get_array(&pdev->dev, "clk", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->clk_gpios))
+		return PTR_ERR(priv->clk_gpios);
+
+	priv->data_gpios = devm_gpiod_get_array(&pdev->dev, "data", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->data_gpios))
+		return PTR_ERR(priv->data_gpios);
+
+	priv->n_ports = priv->clk_gpios->ndescs;
+	priv->n_pins = priv->data_gpios->ndescs;
+
+	priv->shadow = devm_kcalloc(&pdev->dev, priv->n_ports, sizeof(*priv->shadow),
+				    GFP_KERNEL);
+	if (!priv->shadow)
+		return -ENOMEM;
+
+	if (gpio_latch_can_sleep(priv)) {
+		priv->gc.can_sleep = true;
+		priv->gc.set = gpio_latch_set_can_sleep;
+		mutex_init(&priv->mutex);
+	} else {
+		priv->gc.can_sleep = false;
+		priv->gc.set = gpio_latch_set;
+		spin_lock_init(&priv->spinlock);
+	}
+	
+	priv->gc.get_direction = gpio_latch_get_direction;
+	priv->gc.ngpio = priv->n_ports * priv->n_pins;
+	priv->gc.owner = THIS_MODULE;
+	priv->gc.base = -1;
+	priv->gc.parent = &pdev->dev;
+	priv->gc.of_node = pdev->dev.of_node;
+
+	platform_set_drvdata(pdev, priv);
+
+	return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv);
+}
+
+static struct platform_driver gpio_latch_driver = {
+	.driver	= {
+		.name		= "gpio-latch",
+		.of_match_table	= gpio_latch_ids,
+	},
+	.probe	= gpio_latch_probe,
+};
+module_platform_driver(gpio_latch_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
+MODULE_DESCRIPTION("GPIO latch driver");
-- 
2.30.2

[PATCH 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Sascha Hauer]

This adds a binding for a GPIO multiplexer driver based on latches
connected to other GPIOs.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 .../devicetree/bindings/gpio/gpio-latch.yaml  | 83 +++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-latch.yaml

diff --git a/Documentation/devicetree/bindings/gpio/gpio-latch.yaml b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
new file mode 100644
index 0000000000000..0652c9d2130af
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
@@ -0,0 +1,83 @@
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/gpio-latch.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: GPIO latch controller
+
+maintainers:
+  - Sascha Hauer <s.hauer@pengutronix.de>
+
+description: |
+  This binding describes a GPIO multiplexer based on latches connected to
+  other GPIOs, like this:
+
+  CLK0 ----------------------.        ,--------.
+  CLK1 -------------------.  `--------|>    #0 |
+                          |           |        |
+  OUT0 ----------------+--|-----------|D0    Q0|-----|<
+  OUT1 --------------+-|--|-----------|D1    Q1|-----|<
+  OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
+  OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
+  OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
+  OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
+  OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
+  OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
+         | | | | | | | |  |           `--------'
+         | | | | | | | |  |
+         | | | | | | | |  |           ,--------.
+         | | | | | | | |  `-----------|>    #1 |
+         | | | | | | | |              |        |
+         | | | | | | | `--------------|D0    Q0|-----|<
+         | | | | | | `----------------|D1    Q1|-----|<
+         | | | | | `------------------|D2    Q2|-----|<
+         | | | | `--------------------|D3    Q3|-----|<
+         | | | `----------------------|D4    Q4|-----|<
+         | | `------------------------|D5    Q5|-----|<
+         | `--------------------------|D6    Q6|-----|<
+         `----------------------------|D7    Q7|-----|<
+                                      `--------'
+
+  The number of clk-gpios and data-gpios is not fixed. The actual number of
+  GPIOs used for clk and data are taken from the corresponding array lengths.
+
+properties:
+  compatible:
+    const: gpio-latch
+  "#gpio-cells":
+    const: 2
+
+  clk-gpios:
+    description: Array of GPIOs to be used to clock a latch
+
+  data-gpios:
+    description: Array of GPIOs to be used as data GPIOs
+
+  gpio-controller: true
+
+  gpio-line-names: true
+
+required:
+  - compatible
+  - "#gpio-cells"
+  - gpio-controller
+  - clk-gpios
+  - data-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    gpio-latch {
+        #gpio-cells = <2>;
+        pinctrl-names = "default";
+        pinctrl-0 = <&pinctrl_di_do_leds>;
+        compatible = "gpio-latch";
+        gpio-controller;
+
+        clk-gpios = <&gpio3 7 0>, <&gpio3 8 0>;
+        data-gpios = <&gpio3 21 0>, <&gpio3 22 0>,
+                     <&gpio3 23 0>, <&gpio3 24 0>,
+                     <&gpio3 25 0>, <&gpio3 26 0>,
+                     <&gpio3 27 0>, <&gpio3 28 0>;
+    };
-- 
2.30.2

Re: [PATCH 1/2] gpio: Add gpio latch driver

[Marco Felsch]

Hi Sascha,

nice patche, please see inline.

On 22-08-25, Sascha Hauer wrote:
> This driver implements a GPIO multiplexer based on latches connected to
> other GPIOs. A set of data GPIOs is connected to the data input of
> multiple latches. The clock input of each latch is driven by another
> set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
> 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
> are output only.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  drivers/gpio/Kconfig      |   6 ++
>  drivers/gpio/Makefile     |   1 +
>  drivers/gpio/gpio-latch.c | 188 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 195 insertions(+)
>  create mode 100644 drivers/gpio/gpio-latch.c
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 0642f579196f2..e4603810ec910 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -1690,6 +1690,12 @@ config GPIO_AGGREGATOR
>  	      industrial control context, to be operated from userspace using
>  	      the GPIO chardev interface.
>  
> +config GPIO_LATCH
> +	tristate "GPIO latch driver"
> +	help
> +	  Say yes here to enable a driver for GPIO multiplexers based on latches
> +	  connected to other GPIOs.
> +
>  config GPIO_MOCKUP
>  	tristate "GPIO Testing Driver"
>  	select IRQ_SIM
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index a0985d30f51bb..310fa08decc69 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -75,6 +75,7 @@ obj-$(CONFIG_GPIO_IT87)			+= gpio-it87.o
>  obj-$(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_LOGICVC)		+= gpio-logicvc.o
>  obj-$(CONFIG_GPIO_LOONGSON1)		+= gpio-loongson1.o
>  obj-$(CONFIG_GPIO_LOONGSON)		+= gpio-loongson.o
> diff --git a/drivers/gpio/gpio-latch.c b/drivers/gpio/gpio-latch.c
> new file mode 100644
> index 0000000000000..117fcadf76a51
> --- /dev/null
> +++ b/drivers/gpio/gpio-latch.c
> @@ -0,0 +1,188 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * GPIO latch driver
> + *
> + *  Copyright (C) 2022 Sascha Hauer <s.hauer@pengutronix.de>
> + *
> + * This driver implements a GPIO (or better GPO as there is no input)
> + * multiplexer based on latches like this:
> + *
> + * CLK0 ----------------------.        ,--------.
> + * CLK1 -------------------.  `--------|>    #0 |
> + *                         |           |        |
> + * OUT0 ----------------+--|-----------|D0    Q0|-----|<
> + * OUT1 --------------+-|--|-----------|D1    Q1|-----|<
> + * OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
> + * OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
> + * OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
> + * OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
> + * OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
> + * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
> + *        | | | | | | | |  |           `--------'
> + *        | | | | | | | |  |
> + *        | | | | | | | |  |           ,--------.
> + *        | | | | | | | |  `-----------|>    #1 |
> + *        | | | | | | | |              |        |
> + *        | | | | | | | `--------------|D0    Q0|-----|<
> + *        | | | | | | `----------------|D1    Q1|-----|<
> + *        | | | | | `------------------|D2    Q2|-----|<
> + *        | | | | `--------------------|D3    Q3|-----|<
> + *        | | | `----------------------|D4    Q4|-----|<
> + *        | | `------------------------|D5    Q5|-----|<
> + *        | `--------------------------|D6    Q6|-----|<
> + *        `----------------------------|D7    Q7|-----|<
> + *                                     `--------'
> + *
> + * The above is just an example. The actual number of number of latches and
> + * the number of inputs per latch is derived from the number of GPIOs given
> + * in the corresponding device tree properties.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/platform_device.h>
> +#include <linux/gpio/consumer.h>
> +
> +#include "gpiolib.h"
> +
> +struct gpio_latch_priv {
> +	struct gpio_chip gc;
> +	struct gpio_descs *clk_gpios;
> +	struct gpio_descs *data_gpios;
> +	spinlock_t lock;
> +	int n_ports;
> +	int n_pins;
> +	unsigned int *shadow;
> +	struct mutex mutex;
> +	spinlock_t spinlock;
> +};
> +
> +static const struct of_device_id gpio_latch_ids[] = {
> +	{
> +		.compatible	= "gpio-latch",
> +	}, {
> +		/* sentinel */
> +	}
> +};
> +MODULE_DEVICE_TABLE(of, gpio_latch_ids);

Nit normally this is at the end of the file.

> +static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
> +{
> +	return GPIO_LINE_DIRECTION_OUT;
> +}
> +
> +static void __gpio_latch_set(struct gpio_latch_priv *priv, unsigned int offset, int val)
> +{
> +	int latch = offset / priv->n_pins;
> +	int i;
> +
> +	if (val)
> +		priv->shadow[latch] |= BIT(offset % priv->n_pins);
> +	else
> +		priv->shadow[latch] &= ~BIT(offset % priv->n_pins);
> +
> +	for (i = 0; i < priv->n_pins; i++)
> +		gpiod_set_value(priv->data_gpios->desc[i], priv->shadow[latch] & BIT(i));
> +
> +	gpiod_set_value(priv->clk_gpios->desc[latch], 1);
> +	gpiod_set_value(priv->clk_gpios->desc[latch], 0);

Your have two access function for _can_sleep and "can not sleep" but
here you don't resepect it.

Regards,
  Marco

> +}
> +
> +static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
> +{
> +	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&priv->spinlock, flags);
> +
> +	__gpio_latch_set(priv, offset, val);
> +
> +	spin_unlock_irqrestore(&priv->spinlock, flags);
> +}
> +
> +static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
> +{
> +	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
> +
> +	mutex_lock(&priv->mutex);
> +
> +	__gpio_latch_set(priv, offset, val);
> +
> +	mutex_unlock(&priv->mutex);
> +}
> +
> +static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv)
> +{
> +	int i;
> +
> +	for (i = 0; i < priv->n_ports; i++)
> +		if (gpiod_cansleep(priv->clk_gpios->desc[i]))
> +			return true;
> +
> +	for (i = 0; i < priv->n_pins; i++)
> +		if (gpiod_cansleep(priv->data_gpios->desc[i]))
> +			return true;
> +	
> +	return false;
> +}
> +
> +static int gpio_latch_probe(struct platform_device *pdev)
> +{
> +	struct gpio_latch_priv *priv;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->clk_gpios = devm_gpiod_get_array(&pdev->dev, "clk", GPIOD_OUT_LOW);
> +	if (IS_ERR(priv->clk_gpios))
> +		return PTR_ERR(priv->clk_gpios);
> +
> +	priv->data_gpios = devm_gpiod_get_array(&pdev->dev, "data", GPIOD_OUT_LOW);
> +	if (IS_ERR(priv->data_gpios))
> +		return PTR_ERR(priv->data_gpios);
> +
> +	priv->n_ports = priv->clk_gpios->ndescs;
> +	priv->n_pins = priv->data_gpios->ndescs;
> +
> +	priv->shadow = devm_kcalloc(&pdev->dev, priv->n_ports, sizeof(*priv->shadow),
> +				    GFP_KERNEL);
> +	if (!priv->shadow)
> +		return -ENOMEM;
> +
> +	if (gpio_latch_can_sleep(priv)) {
> +		priv->gc.can_sleep = true;
> +		priv->gc.set = gpio_latch_set_can_sleep;
> +		mutex_init(&priv->mutex);
> +	} else {
> +		priv->gc.can_sleep = false;
> +		priv->gc.set = gpio_latch_set;
> +		spin_lock_init(&priv->spinlock);
> +	}
> +	
> +	priv->gc.get_direction = gpio_latch_get_direction;
> +	priv->gc.ngpio = priv->n_ports * priv->n_pins;
> +	priv->gc.owner = THIS_MODULE;
> +	priv->gc.base = -1;
> +	priv->gc.parent = &pdev->dev;
> +	priv->gc.of_node = pdev->dev.of_node;
> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv);
> +}
> +
> +static struct platform_driver gpio_latch_driver = {
> +	.driver	= {
> +		.name		= "gpio-latch",
> +		.of_match_table	= gpio_latch_ids,
> +	},
> +	.probe	= gpio_latch_probe,
> +};
> +module_platform_driver(gpio_latch_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
> +MODULE_DESCRIPTION("GPIO latch driver");
> -- 
> 2.30.2
> 
> 
> 

Re: [PATCH 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Linus Walleij]

On Thu, Aug 25, 2022 at 11:41 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:

> This adds a binding for a GPIO multiplexer driver based on latches
> connected to other GPIOs.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Nice overall!

> +++ b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
> @@ -0,0 +1,83 @@
> +%YAML 1.2

No license?

> +  data-gpios:
> +    description: Array of GPIOs to be used as data GPIOs

Hm I wanted to just call these "gpios" but that is maybe confusing.
What about "latch-gpios"?

Yours,
Linus Walleij

Re: [PATCH 1/2] gpio: Add gpio latch driver

[Linus Walleij]

On Thu, Aug 25, 2022 at 11:41 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:

> This driver implements a GPIO multiplexer based on latches connected to
> other GPIOs. A set of data GPIOs is connected to the data input of
> multiple latches. The clock input of each latch is driven by another
> set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
> 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
> are output only.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Take a close look at the other forwarding driver:
drivers/gpio/gpio-aggregator.c

Especially (as pointed out by Marco) the sleeping/non-sleeping calls.

There was a lot of discussion around that patch before we got the
forwarding of GPIOs into a nice working shape.

Also get Geert to review this because he knows what you need to
do. :)

Yours,
Linus Walleij

Re: [PATCH 1/2] gpio: Add gpio latch driver

[Sascha Hauer]

Hi Marco,

On Fri, Aug 26, 2022 at 07:53:07AM +0200, Marco Felsch wrote:
> Hi Sascha,
> 
> nice patche, please see inline.
> 
> On 22-08-25, Sascha Hauer wrote:
> > This driver implements a GPIO multiplexer based on latches connected to
> > other GPIOs. A set of data GPIOs is connected to the data input of
> > multiple latches. The clock input of each latch is driven by another
> > set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
> > 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
> > are output only.
> > 

[snip]

> > +
> > +static void __gpio_latch_set(struct gpio_latch_priv *priv, unsigned int offset, int val)
> > +{
> > +	int latch = offset / priv->n_pins;
> > +	int i;
> > +
> > +	if (val)
> > +		priv->shadow[latch] |= BIT(offset % priv->n_pins);
> > +	else
> > +		priv->shadow[latch] &= ~BIT(offset % priv->n_pins);
> > +
> > +	for (i = 0; i < priv->n_pins; i++)
> > +		gpiod_set_value(priv->data_gpios->desc[i], priv->shadow[latch] & BIT(i));
> > +
> > +	gpiod_set_value(priv->clk_gpios->desc[latch], 1);
> > +	gpiod_set_value(priv->clk_gpios->desc[latch], 0);
> 
> Your have two access function for _can_sleep and "can not sleep" but
> here you don't resepect it.

I thought the gpio framework would pick the right implementation
automatically. Apparently it doesn't. Will fix in v2.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
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Re: [PATCH 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Sascha Hauer]

Hi Linus,

On Fri, Aug 26, 2022 at 03:37:40PM +0200, Linus Walleij wrote:
> On Thu, Aug 25, 2022 at 11:41 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> > This adds a binding for a GPIO multiplexer driver based on latches
> > connected to other GPIOs.
> >
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> 
> Nice overall!
> 
> > +++ b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
> > @@ -0,0 +1,83 @@
> > +%YAML 1.2
> 
> No license?

Will add in v2.

> 
> > +  data-gpios:
> > +    description: Array of GPIOs to be used as data GPIOs
> 
> Hm I wanted to just call these "gpios" but that is maybe confusing.
> What about "latch-gpios"?

Hm, the clk input is used to latch the current state of the inputs to
the outputs, so "latch-gpios" might even be confused with the GPIO
routed to the clk unput of the latch.  Overall, the whole thing is a
latch, so "latch-gpios" doesn't sound like a good name to distinguish
the different types of inputs of a latch.  I still like data-gpios best
as these lines are described as "Data inputs" in my 74273 data sheet.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Re: [PATCH 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Linus Walleij]

On Mon, Aug 29, 2022 at 4:40 PM Sascha Hauer <s.hauer@pengutronix.de> wrote:

> > Hm I wanted to just call these "gpios" but that is maybe confusing.
> > What about "latch-gpios"?
>
> Hm, the clk input is used to latch the current state of the inputs to
> the outputs, so "latch-gpios" might even be confused with the GPIO
> routed to the clk unput of the latch.  Overall, the whole thing is a
> latch, so "latch-gpios" doesn't sound like a good name to distinguish
> the different types of inputs of a latch.  I still like data-gpios best
> as these lines are described as "Data inputs" in my 74273 data sheet.

How about "latched-gpios" (notice the "d")

It makes some semantic sense.

But I will not nitpick, data is fine, just a bit unspecific.

Yours,
Linus Walleij

Re: [PATCH 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Sascha Hauer]

On Wed, Aug 31, 2022 at 02:40:13PM +0200, Linus Walleij wrote:
> On Mon, Aug 29, 2022 at 4:40 PM Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> > > Hm I wanted to just call these "gpios" but that is maybe confusing.
> > > What about "latch-gpios"?
> >
> > Hm, the clk input is used to latch the current state of the inputs to
> > the outputs, so "latch-gpios" might even be confused with the GPIO
> > routed to the clk unput of the latch.  Overall, the whole thing is a
> > latch, so "latch-gpios" doesn't sound like a good name to distinguish
> > the different types of inputs of a latch.  I still like data-gpios best
> > as these lines are described as "Data inputs" in my 74273 data sheet.
> 
> How about "latched-gpios" (notice the "d")

Fine with me.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |