[PATCH v2 1/3] gpio/mockup: add virtual gpio device

[Bamvor Jian Zhang <bamvor.zhangjian@xxxxxxxxxx>]

This patch add basic structure of a virtual gpio device(gpio-mockup)
for testing gpio subsystem. The tester could manipulate such device
through userspace(sysfs or char device) and check the result from
debugfs.

Currently, it support one or more gpiochip(determined by module
parameters with base,ngpio pair). One could test the overlap of
different gpiochip and test the direction and/or output values of
these chips.

Signed-off-by: Kamlakant Patel <kamlakant.patel@xxxxxxxxxx>
Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@xxxxxxxxxx>
---
 Documentation/kernel-parameters.txt |   4 +
 drivers/gpio/Kconfig                |  12 ++
 drivers/gpio/Makefile               |   1 +
 drivers/gpio/gpio-mockup.c          | 230 ++++++++++++++++++++++++++++++++++++
 4 files changed, 247 insertions(+)
 create mode 100644 drivers/gpio/gpio-mockup.c

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 742f69d..cc0ce8a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1278,6 +1278,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
 			Default: 1024
 
+	gpio-mockup.gpio_mockup_ranges
+			[HW] Sets the ranges of gpiochip of for this device.
+			Format: <start1>,<end1>,<start2>,<end2>...
+
 	hardlockup_all_cpu_backtrace=
 			[KNL] Should the hard-lockup detector generate
 			backtraces on all cpus.
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index cb212eb..59bebca 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -268,6 +268,18 @@ config GPIO_MM_LANTIQ
 	  (EBU) found on Lantiq SoCs. The gpios are output only as they are
 	  created by attaching a 16bit latch to the bus.
 
+config GPIO_MOCKUP
+	tristate "GPIO Testing Driver"
+	depends on GPIOLIB
+	select GPIO_SYSFS
+	help
+	  This enables GPIO Testing driver, which provides a way to test GPIO
+	  subsystem through sysfs(or char device) and debugfs. GPIO_SYSFS
+	  must be selected for this test.
+	  User could use it through the script in
+	  tools/testing/selftests/gpio/gpio-mockup.sh. Reference the usage in
+	  it.
+
 config GPIO_MOXART
 	bool "MOXART GPIO support"
 	depends on ARCH_MOXART
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 548e9b5..2635e4a 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -63,6 +63,7 @@ obj-$(CONFIG_GPIO_MC9S08DZ60)	+= gpio-mc9s08dz60.o
 obj-$(CONFIG_GPIO_MCP23S08)	+= gpio-mcp23s08.o
 obj-$(CONFIG_GPIO_ML_IOH)	+= gpio-ml-ioh.o
 obj-$(CONFIG_GPIO_MM_LANTIQ)	+= gpio-mm-lantiq.o
+obj-$(CONFIG_GPIO_MOCKUP)      += gpio-mockup.o
 obj-$(CONFIG_GPIO_MOXART)	+= gpio-moxart.o
 obj-$(CONFIG_GPIO_MPC5200)	+= gpio-mpc5200.o
 obj-$(CONFIG_GPIO_MPC8XXX)	+= gpio-mpc8xxx.o
diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
new file mode 100644
index 0000000..33b4b6a
--- /dev/null
+++ b/drivers/gpio/gpio-mockup.c
@@ -0,0 +1,230 @@
+/*
+ * GPIO Testing Device Driver
+ *
+ * Copyright (C) 2014  Kamlakant Patel <kamlakant.patel@xxxxxxxxxxxx>
+ * Copyright (C) 2015-2016  Bamvor Jian Zhang <bamvor.zhangjian@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/gpio/driver.h>
+#include <linux/platform_device.h>
+
+#define GPIO_NAME	"gpio-mockup"
+#define	MAX_GC		10
+
+enum direction {
+	IN,
+	OUT
+};
+
+/*
+ * struct gpio_pin_status - structure describing a GPIO status
+ * @dir:       Configures direction of gpio as "in" or "out", 0=in, 1=out
+ * @value:     Configures status of the gpio as 0(low) or 1(high)
+ */
+struct gpio_pin_status {
+	enum direction	dir;
+	bool		value;
+};
+
+struct mockup_gpio_controller {
+	struct gpio_chip	gc;
+	struct gpio_pin_status	*stats;
+};
+
+static int gpio_mockup_ranges[MAX_GC << 1];
+static int gpio_mockup_params_nr;
+module_param_array(gpio_mockup_ranges, int, &gpio_mockup_params_nr, 0400);
+
+static const char *pins_name_start = "A";
+
+static int
+mockup_gpio_get(struct gpio_chip *gc, unsigned offset)
+{
+	struct mockup_gpio_controller *cntr = container_of(gc,
+			struct mockup_gpio_controller, gc);
+
+	return cntr->stats[offset].value;
+}
+
+static void
+mockup_gpio_set(struct gpio_chip *gc, unsigned offset, int value)
+{
+	struct mockup_gpio_controller *cntr = container_of(gc,
+			struct mockup_gpio_controller, gc);
+
+	cntr->stats[offset].value = !!value;
+}
+
+static int
+mockup_gpio_dirout(struct gpio_chip *gc, unsigned offset, int value)
+{
+	struct mockup_gpio_controller *cntr = container_of(gc,
+			struct mockup_gpio_controller, gc);
+
+	mockup_gpio_set(gc, offset, value);
+	cntr->stats[offset].dir = OUT;
+	return 0;
+}
+
+static int
+mockup_gpio_dirin(struct gpio_chip *gc, unsigned offset)
+{
+	struct mockup_gpio_controller *cntr = container_of(gc,
+			struct mockup_gpio_controller, gc);
+
+	cntr->stats[offset].dir = IN;
+	return 0;
+}
+
+static int
+mockup_gpio_add(struct device *dev, struct mockup_gpio_controller *cntr,
+		const char *name, int base, int ngpio)
+{
+	int ret;
+
+	cntr->gc.base = base;
+	cntr->gc.ngpio = ngpio;
+	cntr->gc.label = name;
+	cntr->gc.owner = THIS_MODULE;
+	cntr->gc.parent = dev;
+	cntr->gc.get = mockup_gpio_get;
+	cntr->gc.set = mockup_gpio_set;
+	cntr->gc.direction_output = mockup_gpio_dirout;
+	cntr->gc.direction_input = mockup_gpio_dirin;
+	cntr->stats = devm_kzalloc(dev, sizeof(*cntr->stats) * cntr->gc.ngpio,
+			GFP_KERNEL);
+	if (!cntr->stats) {
+		ret = -ENOMEM;
+		goto err;
+	}
+	ret = gpiochip_add(&cntr->gc);
+	if (ret)
+		goto err;
+
+	dev_info(dev, "gpio<%d..%d> add successful!", base, base + ngpio);
+	return 0;
+err:
+	dev_err(dev, "gpio<%d..%d> add failed!", base, base + ngpio);
+	return ret;
+}
+
+static int
+mockup_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mockup_gpio_controller *cntr;
+	int ret;
+	int i, j;
+	int base;
+	int ngpio;
+
+	if (gpio_mockup_params_nr < 2)
+		return -EINVAL;
+
+	cntr = devm_kzalloc(dev, sizeof(*cntr) * (gpio_mockup_params_nr >> 1),
+			GFP_KERNEL);
+	if (!cntr)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, cntr);
+
+	for (i = 0; i < gpio_mockup_params_nr >> 1; i++) {
+		base = gpio_mockup_ranges[i * 2];
+		if (base == -1)
+			ngpio = gpio_mockup_ranges[i * 2 + 1];
+		else
+			ngpio = gpio_mockup_ranges[i * 2 + 1] - base;
+
+		if (ngpio >= 0)
+			ret = mockup_gpio_add(dev, &cntr[i],
+					pins_name_start + i,
+					base, ngpio);
+		else
+			ret = -1;
+
+		if (ret) {
+			if (base < 0)
+				dev_err(dev, "gpio<%d..%d> add failed, remove added gpio\n",
+						base, ngpio);
+			else
+				dev_err(dev, "gpio<%d..%d> add failed, remove added gpio\n",
+						base, base + ngpio);
+
+			for (j = 0; j < i; j++)
+				gpiochip_remove(&cntr[j].gc);
+
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static int
+mockup_gpio_remove(struct platform_device *pdev)
+{
+	struct mockup_gpio_controller *cntr = platform_get_drvdata(pdev);
+	int i;
+
+	for (i = 0; i < gpio_mockup_params_nr >> 1; i++)
+		gpiochip_remove(&cntr[i].gc);
+
+	return 0;
+}
+
+static struct platform_driver mockup_gpio_driver = {
+	.driver = {
+		.name           = GPIO_NAME,
+	},
+	.probe = mockup_gpio_probe,
+	.remove = mockup_gpio_remove,
+};
+
+static struct platform_device *pdev;
+static int __init
+mock_device_init(void)
+{
+	int err;
+
+	pdev = platform_device_alloc(GPIO_NAME, -1);
+	if (!pdev)
+		return -ENOMEM;
+
+	err = platform_device_add(pdev);
+	if (err) {
+		platform_device_put(pdev);
+		return err;
+	}
+
+	err = platform_driver_register(&mockup_gpio_driver);
+	if (err) {
+		platform_device_unregister(pdev);
+		return err;
+	}
+
+	return 0;
+}
+
+static void __exit
+mock_device_exit(void)
+{
+	platform_driver_unregister(&mockup_gpio_driver);
+	platform_device_unregister(pdev);
+}
+
+module_init(mock_device_init);
+module_exit(mock_device_exit);
+
+MODULE_AUTHOR("Kamlakant Patel <kamlakant.patel@xxxxxxxxxxxx>");
+MODULE_AUTHOR("Bamvor Jian Zhang <bamvor.zhangjian@xxxxxxxxxx>");
+MODULE_DESCRIPTION("GPIO Testing driver");
+MODULE_LICENSE("GPL v2");
+
-- 
2.1.4

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