From: AKASHI Takahiro <takahiro.akashi@linaro.org>
The ARM SCMI pinctrl protocol allows GPIO access. Instead of creating
a new SCMI gpio driver, this driver is a generic GPIO driver that uses
standard pinctrl interfaces.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
drivers/gpio/Kconfig | 7 ++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-by-pinctrl.c | 124 +++++++++++++++++++++++++++++++++
3 files changed, 132 insertions(+)
create mode 100644 drivers/gpio/gpio-by-pinctrl.c
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index b45fb799e36c..4c8d2589c412 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -246,6 +246,13 @@ config GPIO_BRCMSTB
help
Say yes here to enable GPIO support for Broadcom STB (BCM7XXX) SoCs.
+config GPIO_BY_PINCTRL
+ tristate "GPIO support based on a pure pin control backend"
+ depends on GPIOLIB
+ help
+ Select this option to support GPIO devices based solely on pin
+ control. This is used to do GPIO over the ARM SCMI protocol.
+
config GPIO_CADENCE
tristate "Cadence GPIO support"
depends on OF_GPIO
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index c05f7d795c43..20d4a57afdaa 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -51,6 +51,7 @@ obj-$(CONFIG_GPIO_BD9571MWV) += gpio-bd9571mwv.o
obj-$(CONFIG_GPIO_BLZP1600) += gpio-blzp1600.o
obj-$(CONFIG_GPIO_BRCMSTB) += gpio-brcmstb.o
obj-$(CONFIG_GPIO_BT8XX) += gpio-bt8xx.o
+obj-$(CONFIG_GPIO_BY_PINCTRL) += gpio-by-pinctrl.o
obj-$(CONFIG_GPIO_CADENCE) += gpio-cadence.o
obj-$(CONFIG_GPIO_CGBC) += gpio-cgbc.o
obj-$(CONFIG_GPIO_CLPS711X) += gpio-clps711x.o
diff --git a/drivers/gpio/gpio-by-pinctrl.c b/drivers/gpio/gpio-by-pinctrl.c
new file mode 100644
index 000000000000..51d99723d3ca
--- /dev/null
+++ b/drivers/gpio/gpio-by-pinctrl.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Copyright (C) 2023 Linaro Inc.
+// Author: AKASHI takahiro <takahiro.akashi@linaro.org>
+
+#include <linux/gpio/driver.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include "gpiolib.h"
+
+struct pin_control_gpio_priv {
+ struct gpio_chip chip;
+};
+
+static int pin_control_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+ unsigned long config;
+ bool in, out;
+ int ret;
+
+ config = PIN_CONFIG_INPUT_ENABLE;
+ ret = pinctrl_gpio_get_config(gc, offset, &config);
+ if (ret)
+ return ret;
+ in = config;
+
+ config = PIN_CONFIG_OUTPUT_ENABLE;
+ ret = pinctrl_gpio_get_config(gc, offset, &config);
+ if (ret)
+ return ret;
+ out = config;
+
+ /* Consistency check - in theory both can be enabled! */
+ if (in && !out)
+ return GPIO_LINE_DIRECTION_IN;
+ if (!in && out)
+ return GPIO_LINE_DIRECTION_OUT;
+
+ return -EINVAL;
+}
+
+static int pin_control_gpio_direction_output(struct gpio_chip *chip,
+ unsigned int offset, int val)
+{
+ return pinctrl_gpio_direction_output(chip, offset);
+}
+
+static int pin_control_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+ unsigned long config;
+ int ret;
+
+ config = PIN_CONFIG_LEVEL;
+ ret = pinctrl_gpio_get_config(chip, offset, &config);
+ if (ret)
+ return ret;
+
+ return !!config;
+}
+
+static int pin_control_gpio_set(struct gpio_chip *chip, unsigned int offset,
+ int val)
+{
+ unsigned long config;
+
+ config = PIN_CONF_PACKED(PIN_CONFIG_LEVEL, val);
+ return pinctrl_gpio_set_config(chip, offset, config);
+}
+
+static int pin_control_gpio_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct pin_control_gpio_priv *priv;
+ struct gpio_chip *chip;
+ int ret;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ chip = &priv->chip;
+ chip->label = dev_name(dev);
+ chip->parent = dev;
+ chip->base = -1;
+
+ chip->request = gpiochip_generic_request;
+ chip->free = gpiochip_generic_free;
+ chip->get_direction = pin_control_gpio_get_direction;
+ chip->direction_input = pinctrl_gpio_direction_input;
+ chip->direction_output = pin_control_gpio_direction_output;
+ chip->get = pin_control_gpio_get;
+ chip->set = pin_control_gpio_set;
+ chip->set_config = gpiochip_generic_config;
+
+ ret = devm_gpiochip_add_data(dev, chip, priv);
+ if (ret)
+ return ret;
+
+ platform_set_drvdata(pdev, priv);
+
+ return 0;
+}
+
+static const struct of_device_id pin_control_gpio_match[] = {
+ { .compatible = "scmi-pinctrl-gpio" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, pin_control_gpio_match);
+
+static struct platform_driver pin_control_gpio_driver = {
+ .probe = pin_control_gpio_probe,
+ .driver = {
+ .name = "pin-control-gpio",
+ .of_match_table = pin_control_gpio_match,
+ },
+};
+module_platform_driver(pin_control_gpio_driver);
+
+MODULE_AUTHOR("AKASHI Takahiro <takahiro.akashi@linaro.org>");
+MODULE_DESCRIPTION("Pinctrl based GPIO driver");
+MODULE_LICENSE("GPL");
--
2.51.0On Tue, Mar 17, 2026 at 05:41:02PM +0300, Dan Carpenter wrote:
> The ARM SCMI pinctrl protocol allows GPIO access. Instead of creating
> a new SCMI gpio driver, this driver is a generic GPIO driver that uses
GPIO
> standard pinctrl interfaces.
...
> +config GPIO_BY_PINCTRL
> + tristate "GPIO support based on a pure pin control backend"
> + depends on GPIOLIB
> + help
> + Select this option to support GPIO devices based solely on pin
> + control. This is used to do GPIO over the ARM SCMI protocol.
This is not enough to understand (as discussion in previous round showed).
Can we have added a Documentation/driver-api/gpio/... (to the existing one
or a new one)?
...
> +// Copyright (C) 2023 Linaro Inc.
2026 (as well)?
...
+ errno.h // -ENOMEM, et cetera
> +#include <linux/gpio/driver.h>
> +#include <linux/list.h>
?! Cargo cult?
+ mod_devicetable.h // of_device_id
> +#include <linux/module.h>
> +#include <linux/pinctrl/consumer.h>
> +#include <linux/platform_device.h>
> +#include <linux/types.h>
+ blank line.
> +#include "gpiolib.h"
...
> +struct pin_control_gpio_priv {
> + struct gpio_chip chip;
> +};
Unneeded, you can use struct gpio_chip directly. No?
...
> +static int pin_control_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
> +{
> + unsigned long config;
> + bool in, out;
> + int ret;
> +
> + config = PIN_CONFIG_INPUT_ENABLE;
> + ret = pinctrl_gpio_get_config(gc, offset, &config);
> + if (ret)
> + return ret;
> + in = config;
> +
> + config = PIN_CONFIG_OUTPUT_ENABLE;
> + ret = pinctrl_gpio_get_config(gc, offset, &config);
> + if (ret)
> + return ret;
> + out = config;
> + /* Consistency check - in theory both can be enabled! */
> + if (in && !out)
> + return GPIO_LINE_DIRECTION_IN;
> + if (!in && out)
> + return GPIO_LINE_DIRECTION_OUT;
> +
> + return -EINVAL;
When both are enabled it's out direction, so the entire piece
can be simplified to
if (out)
return GPIO_LINE_DIRECTION_OUT;
if (in)
return GPIO_LINE_DIRECTION_IN;
return ...something...; ideally it should be HiZ.
So, even more simplified will be just
if (out)
return GPIO_LINE_DIRECTION_OUT;
else
return GPIO_LINE_DIRECTION_IN;
> +}
...
> + ret = devm_gpiochip_add_data(dev, chip, priv);
> + if (ret)
> + return ret;
> +
> + platform_set_drvdata(pdev, priv);
Not used.
> + return 0;
Hence, the entire piece is just
return devm_gpiochip_add_data(dev, chip, priv);
--
With Best Regards,
Andy Shevchenko
© 2016 - 2026 Red Hat, Inc.