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Subject[PATCH 2/2] iio: misc: add support for GPIO power switches
Date
Some power-measuring ADCs work together with power load switches which
allow to power-cycle measured devices.

An example use case would be measuring the power consumption of a
development board during boot using a power monitor such as TI INA226
and power-cycling the board remotely using a TPS229* power switch.

Add an iio driver for simple GPIO power switches and expose a sysfs
attribute allowing to toggle their state.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/iio/Kconfig | 1 +
drivers/iio/Makefile | 1 +
drivers/iio/misc/Kconfig | 17 +++++
drivers/iio/misc/Makefile | 6 ++
drivers/iio/misc/gpio-power-switch.c | 127 +++++++++++++++++++++++++++++++++++
5 files changed, 152 insertions(+)
create mode 100644 drivers/iio/misc/Kconfig
create mode 100644 drivers/iio/misc/Makefile
create mode 100644 drivers/iio/misc/gpio-power-switch.c

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 6743b18..2e896e0 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -80,6 +80,7 @@ source "drivers/iio/gyro/Kconfig"
source "drivers/iio/health/Kconfig"
source "drivers/iio/humidity/Kconfig"
source "drivers/iio/imu/Kconfig"
+source "drivers/iio/misc/Kconfig"
source "drivers/iio/light/Kconfig"
source "drivers/iio/magnetometer/Kconfig"
source "drivers/iio/orientation/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 87e4c43..4008d5a 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -25,6 +25,7 @@ obj-y += frequency/
obj-y += health/
obj-y += humidity/
obj-y += imu/
+obj-y += misc/
obj-y += light/
obj-y += magnetometer/
obj-y += orientation/
diff --git a/drivers/iio/misc/Kconfig b/drivers/iio/misc/Kconfig
new file mode 100644
index 0000000..8d73751
--- /dev/null
+++ b/drivers/iio/misc/Kconfig
@@ -0,0 +1,17 @@
+#
+# Miscellaneous iio drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Miscellaneous iio drivers"
+
+config GPIO_POWER_SWITCH
+ tristate "GPIO power switch driver"
+ depends on GPIOLIB
+ help
+ Say yes here to build support for gpio power switches.
+
+ To compile this driver as a module, choose M here: the module will
+ be called gpio-power-switch.
+
+endmenu
diff --git a/drivers/iio/misc/Makefile b/drivers/iio/misc/Makefile
new file mode 100644
index 0000000..cebd0c4
--- /dev/null
+++ b/drivers/iio/misc/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for IIO misc drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_GPIO_POWER_SWITCH) += gpio-power-switch.o
diff --git a/drivers/iio/misc/gpio-power-switch.c b/drivers/iio/misc/gpio-power-switch.c
new file mode 100644
index 0000000..25fbeb7
--- /dev/null
+++ b/drivers/iio/misc/gpio-power-switch.c
@@ -0,0 +1,127 @@
+/*
+ * GPIO power switch driver using the industrial IO framework.
+ *
+ * Copyright (C) 2016 BayLibre SAS
+ *
+ * Author:
+ * Bartosz Golaszewski <bgolaszewski@baylibre.com.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/gpio/consumer.h>
+
+struct gpio_pwrsw_context {
+ struct gpio_desc *gpio;
+};
+
+static ssize_t gpio_pwrsw_enable_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct gpio_pwrsw_context *ctx = iio_priv(dev_to_iio_dev(dev));
+ int val;
+
+ val = gpiod_get_value_cansleep(ctx->gpio);
+ if (val < 0)
+ return val;
+
+ return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t gpio_pwrsw_enable_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct gpio_pwrsw_context *ctx = iio_priv(dev_to_iio_dev(dev));
+ bool val;
+ int ret;
+
+ ret = strtobool(buf, &val);
+ if (ret)
+ return ret;
+
+ gpiod_set_value_cansleep(ctx->gpio, val ? 1 : 0);
+
+ return len;
+}
+
+static IIO_DEVICE_ATTR(in_active, 0644,
+ gpio_pwrsw_enable_show,
+ gpio_pwrsw_enable_store, 0);
+
+static struct attribute *gpio_pwrsw_attributes[] = {
+ &iio_dev_attr_in_active.dev_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group gpio_pwrsw_attribute_group = {
+ .attrs = gpio_pwrsw_attributes,
+};
+
+static const struct iio_info gpio_pwrsw_info = {
+ .driver_module = THIS_MODULE,
+ .attrs = &gpio_pwrsw_attribute_group,
+};
+
+static int gpio_pwrsw_probe(struct platform_device *pdev)
+{
+ struct gpio_pwrsw_context *ctx;
+ struct iio_dev *iio_dev;
+ const char *name = NULL;
+ struct device *dev;
+ bool init_state;
+ int gpio_flags;
+
+ dev = &pdev->dev;
+
+ iio_dev = devm_iio_device_alloc(dev, sizeof(*ctx));
+ if (!iio_dev)
+ return -ENOMEM;
+
+ ctx = iio_priv(iio_dev);
+
+ init_state = of_property_read_bool(dev->of_node, "power-switch-on");
+ gpio_flags = init_state ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
+
+ ctx->gpio = devm_gpiod_get(dev, "power", gpio_flags);
+ if (IS_ERR(ctx->gpio)) {
+ dev_err(dev, "unable to get the power switch gpio: %ld\n",
+ PTR_ERR(ctx->gpio));
+ return PTR_ERR(ctx->gpio);
+ }
+
+ of_property_read_string(dev->of_node, "power-switch-name", &name);
+
+ iio_dev->dev.parent = dev;
+ iio_dev->dev.of_node = dev->of_node;
+ iio_dev->name = name ? name : dev->driver->name;
+ iio_dev->info = &gpio_pwrsw_info;
+
+ return devm_iio_device_register(dev, iio_dev);
+}
+
+static const struct of_device_id gpio_pwrsw_of_match[] = {
+ { .compatible = "gpio-power-switch", },
+ { },
+};
+
+static struct platform_driver gpio_pwrsw_platform_driver = {
+ .probe = gpio_pwrsw_probe,
+ .driver = {
+ .name = "gpio-power-switch",
+ .of_match_table = gpio_pwrsw_of_match,
+ },
+};
+module_platform_driver(gpio_pwrsw_platform_driver);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bgolaszewski@baylibre.com>");
+MODULE_DESCRIPTION("GPIO power switch driver for iio");
+MODULE_LICENSE("GPL v2");
--
2.9.3
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