[RFD,1/3] gpio/mockup: add virtual gpio device
diff mbox

Message ID 1447491097-14799-2-git-send-email-bamvor.zhangjian@linaro.org
State New
Headers show

Commit Message

Bamvor Jian Zhang Nov. 14, 2015, 8:51 a.m. UTC
This patch add basic structure of a virtual gpio device(gpio-mockup)
for testing gpio subsystem. The tester could manipulate such device
through sysfs 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@linaro.org>
Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
---
 drivers/gpio/Kconfig       |   9 ++
 drivers/gpio/Makefile      |   1 +
 drivers/gpio/gpio-mockup.c | 216 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 226 insertions(+)
 create mode 100644 drivers/gpio/gpio-mockup.c

Comments

Linus Walleij Nov. 26, 2015, 9:34 a.m. UTC | #1
On Sat, Nov 14, 2015 at 9:51 AM, Bamvor Jian Zhang
<bamvor.zhangjian@linaro.org> wrote:

> This patch add basic structure of a virtual gpio device(gpio-mockup)
> for testing gpio subsystem. The tester could manipulate such device
> through sysfs 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@linaro.org>
> Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>

This is looking quite nice. Just minor nitpicks:

> +#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          5
> +
> +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;
> +       int             value;

bool value

Since it is only 0/1.

> +struct mockup_gpio_controller {
> +       struct gpio_chip        gc;
> +       struct gpio_pin_status  *stats;
> +};
> +
> +int conf[MAX_GC << 1];
> +int params_nr;
> +module_param_array(conf, int, &params_nr, 0400);

I don't really understand why we need these.

"params_nr" is a way too generic name, plus such module parameters
should be documented in Documentation/kernel-parameters.txt
gpio_test_chips = n is better, but I don't really see why we need to
specify this at all, can't we just decide how many we need? Why
do we need more than one?

> +const char *pins_name[MAX_GC] = {"A", "B", "C", "D", "E"};

So this has 5 pins. Any special reason why?
I think 32 is more typical, but there may be a point in having some
odd number.

> +
> +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;

This should still work with a bool there I think.

> +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);
> +
> +       if (value)
> +               cntr->stats[offset].value = 1;
> +       else
> +               cntr->stats[offset].value = 0;

Assign like this to do boolean clamping:

cntr->stats[offset].value = !!value;


> +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;

I don't think base should be specified for the test chip.
We should set this to -1 and get a dynamic base, whatever
it is. Then the test scripts should deal with that.

Doing this also makes the conf array go away.

> +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 (params_nr == 0) {
> +               params_nr = 2;
> +               conf[0] = 0;
> +               conf[1] = 32;
> +       }

This needs explaining. Why do we want 2 test gpio chips by default?
Why not just one?

Why is the base of the second one 32 and not 5 since there is 5 pins
on each chip?

I would think adding just one chip or two with very varying characteristics
is the way to go. Like one 32 line chip and one 5 line chip or
something.

> +
> +       cntr = devm_kzalloc(dev, sizeof(*cntr) * params_nr, GFP_KERNEL);
> +       if (!cntr)
> +               return -ENOMEM;
> +
> +       platform_set_drvdata(pdev, cntr);
> +
> +       for (i = 0; i < params_nr >> 1; i++) {
> +               base = conf[i << 1];
> +               ngpio = conf[(i << 1) + 1];

These should go away I think.

The rest looks good.

Yours,
Linus Walleij
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Bamvor Jian Zhang Nov. 26, 2015, 2:54 p.m. UTC | #2
Hi, Linus

On 11/26/2015 05:34 PM, Linus Walleij wrote:
> On Sat, Nov 14, 2015 at 9:51 AM, Bamvor Jian Zhang
> <bamvor.zhangjian@linaro.org> wrote:
> 
>> This patch add basic structure of a virtual gpio device(gpio-mockup)
>> for testing gpio subsystem. The tester could manipulate such device
>> through sysfs 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@linaro.org>
>> Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
> 
> This is looking quite nice. Just minor nitpicks:
Thanks.
> 
>> +#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          5
>> +
>> +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;
>> +       int             value;
> 
> bool value
> 
> Since it is only 0/1.
Ok, I will change it in next version.
> 
>> +struct mockup_gpio_controller {
>> +       struct gpio_chip        gc;
>> +       struct gpio_pin_status  *stats;
>> +};
>> +
>> +int conf[MAX_GC << 1];
>> +int params_nr;
>> +module_param_array(conf, int, &params_nr, 0400);
> 
> I don't really understand why we need these.
> 
> "params_nr" is a way too generic name, plus such module parameters
> should be documented in Documentation/kernel-parameters.txt
> gpio_test_chips = n is better, but I don't really see why we need to
> specify this at all, can't we just decide how many we need? Why
> do we need more than one?
Firstly, one or more gpiochip(s) exist in real driver. And I found the
number of gpiochip may be the corner case. Just like the fix in 
Commit 5433aed ("gpiolib: improve overlap check of range of gpio").
Left this parameter to userspace make the test script easier to
different corner case.
In fact, one or two or more gpiochip is different cases in
gpiochip_add_to_list().
> 
>> +const char *pins_name[MAX_GC] = {"A", "B", "C", "D", "E"};
> 
> So this has 5 pins. Any special reason why?
There is no special reason. Like I said above, I found that there 
are the corner cases when I insert different number of gpiochip. And I
do not want to fix to 3 gpiochips.
And it is not the name of each pin. It is the name of each gpiochip
(cntr->gc.label = name).
> I think 32 is more typical, but there may be a point in having some
> odd number.
Do you mean the gc->names? I do not support it at this time. It seems
that the code of handling gc->names(aka gpiochip_set_desc_names) is
not important. How about do it later?
> 
>> +
>> +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;
> 
> This should still work with a bool there I think.
Ok. 
> 
>> +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);
>> +
>> +       if (value)
>> +               cntr->stats[offset].value = 1;
>> +       else
>> +               cntr->stats[offset].value = 0;
> 
> Assign like this to do boolean clamping:
> 
> cntr->stats[offset].value = !!value;
Got you.
> 
> 
>> +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;
> 
> I don't think base should be specified for the test chip.
> We should set this to -1 and get a dynamic base, whatever
> it is. 
Fix base to -1 means we could only test the path of code in dynamic
gpio base allocation. I had look at the drivers in drivers/gpio,
it seems that the dynamic allocation is not usual. So, I feel test
with the base gave by user(dt, acpi or something else) is useful.
> Then the test scripts should deal with that.

> 
> Doing this also makes the conf array go away.
> 
>> +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 (params_nr == 0) {
>> +               params_nr = 2;
>> +               conf[0] = 0;
>> +               conf[1] = 32;
>> +       }
> 
> This needs explaining. Why do we want 2 test gpio chips by default?
> Why not just one?
Oh, it is too tricky. The default 2 parameter means one gpiochip(one
base and one ngpio). It is indeed just one gpiochip by default.
When I add the module parameter, I was thinking I should pass the
parameter in one array(base1, ngpio1, base2, ngpio2 ...) or two arrays
((base1, base2, ...), (ngpio1, ngpio2, ...). Having two arrays is more
clear but hard to read in test script.
> 
> Why is the base of the second one 32 and not 5 since there is 5 pins
> on each chip?
The '5' is the series of name of each gpio label.
> 
> I would think adding just one chip or two with very varying characteristics
> is the way to go.
Like I mentioned above, one, two or more is different cases.
> Like one 32 line chip and one 5 line chip or
> something.
Yes, it is what I am doing in the script. I will insert one, two or
more gpiochip with different number of lines each.
> 
>> +
>> +       cntr = devm_kzalloc(dev, sizeof(*cntr) * params_nr, GFP_KERNEL);
>> +       if (!cntr)
>> +               return -ENOMEM;
>> +
>> +       platform_set_drvdata(pdev, cntr);
>> +
>> +       for (i = 0; i < params_nr >> 1; i++) {
>> +               base = conf[i << 1];
>> +               ngpio = conf[(i << 1) + 1];
> 
> These should go away I think.
> 
> The rest looks good.
Thanks

Bamvor
> 
> Yours,
> Linus Walleij
> 
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Patch
diff mbox

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index b18bea0..41d8421 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -268,6 +268,15 @@  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 and debugfs. GPIO_SYSFS must be selected for
+	  this test.
+
 config GPIO_MOXART
 	bool "MOXART GPIO support"
 	depends on ARCH_MOXART
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 986dbd8..b91b66c 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -62,6 +62,7 @@  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..b689389
--- /dev/null
+++ b/drivers/gpio/gpio-mockup.c
@@ -0,0 +1,216 @@ 
+/*
+ * GPIO Testing Device Driver
+ *
+ * Copyright (C) 2014  Kamlakant Patel <kamlakant.patel@linaro.org>
+ * Copyright (C) 2015  Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
+ *
+ * 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		5
+
+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;
+	int		value;
+};
+
+struct mockup_gpio_controller {
+	struct gpio_chip	gc;
+	struct gpio_pin_status	*stats;
+};
+
+int conf[MAX_GC << 1];
+int params_nr;
+module_param_array(conf, int, &params_nr, 0400);
+
+const char *pins_name[MAX_GC] = {"A", "B", "C", "D", "E"};
+
+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);
+
+	if (value)
+		cntr->stats[offset].value = 1;
+	else
+		cntr->stats[offset].value = 0;
+
+}
+
+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;
+}
+
+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.dev = 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 (params_nr == 0) {
+		params_nr = 2;
+		conf[0] = 0;
+		conf[1] = 32;
+	}
+
+	cntr = devm_kzalloc(dev, sizeof(*cntr) * params_nr, GFP_KERNEL);
+	if (!cntr)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, cntr);
+
+	for (i = 0; i < params_nr >> 1; i++) {
+		base = conf[i << 1];
+		ngpio = conf[(i << 1) + 1];
+		ret = mockup_gpio_add(dev, &cntr[i], pins_name[i], base, ngpio);
+		if (ret) {
+			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 < 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@linaro.org>");
+MODULE_AUTHOR("Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>");
+MODULE_DESCRIPTION("GPIO Testing driver");
+MODULE_LICENSE("GPL v2");