[PATCH v5 5/8] gpio: sim: new testing module

Bartosz Golaszewski
2021-09-20T14:06:49Z

Implement a new, modern GPIO testing module controlled by configfs
attributes instead of module parameters. The goal of this driver is
to provide a replacement for gpio-mockup that will be easily extensible
with new features and doesn't require reloading the module to change
the setup.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
[Andy: Initialize attribute allocated on the heap]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[Colin: Fix dereference of free'd pointer config]
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
Documentation/admin-guide/gpio/gpio-sim.rst | 72 ++
drivers/gpio/Kconfig | 8 +
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-sim.c | 877 ++++++++++++++++++++
4 files changed, 958 insertions(+)
create mode 100644 Documentation/admin-guide/gpio/gpio-sim.rst
create mode 100644 drivers/gpio/gpio-sim.c

diff --git a/Documentation/admin-guide/gpio/gpio-sim.rst b/Documentation/admin-guide/gpio/gpio-sim.rst
new file mode 100644
index 000000000000..08eac487e35e
--- /dev/null
+++ b/Documentation/admin-guide/gpio/gpio-sim.rst
@@ -0,0 +1,72 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Configfs GPIO Simulator
+=======================
+
+The configfs GPIO Simulator (gpio-sim) provides a way to create simulated GPIO
+chips for testing purposes. The lines exposed by these chips can be accessed
+using the standard GPIO character device interface as well as manipulated
+using sysfs attributes.
+
+Creating simulated chips
+------------------------
+
+The gpio-sim module registers a configfs subsystem called 'gpio-sim'. It's a
+subsystem with committable items which means two subdirectories are created in
+the filesystem: pending and live. For more information on configfs and
+committable items, please refer to Documentation/filesystems/configfs.rst.
+
+In order to instantiate a new simulated chip, the user needs to mkdir() a new
+directory in pending/. Inside each new directory, there's a set of attributes
+that can be used to configure the new chip. Once the configuration is complete,
+the user needs to use rename() to move the chip to the live/ directory. This
+creates and registers the new device.
+
+In order to destroy a simulated chip, it has to be moved back to pending first
+and then removed using rmdir().
+
+Currently supported configuration attributes are:
+
+ num_lines - an unsigned integer value defining the number of GPIO lines to
+ export
+
+ label - a string defining the label for the GPIO chip
+
+ line_names - a list of GPIO line names in the form of quoted strings
+ separated by commas, e.g.: '"foo", "bar", "", "foobar"'. The
+ number of strings doesn't have to be equal to the value set in
+ the num_lines attribute. If it's lower than the number of lines,
+ the remaining lines are unnamed. If it's larger, the superfluous
+ lines are ignored. A name of the form: '""' means the line
+ should be unnamed.
+
+Additionally two read-only attributes named 'chip_name' and 'dev_name' are
+exposed in order to provide users with a mapping from configfs directories to
+the actual devices created in the kernel. The former returns the name of the
+GPIO device as assigned by gpiolib (i.e. "gpiochip0", "gpiochip1", etc.). The
+latter returns the parent device name as defined by the gpio-sim driver (i.e.
+"gpio-sim.0", "gpio-sim.1", etc.). This allows user-space to map the configfs
+items both to the correct character device file as well as the associated entry
+in sysfs.
+
+Simulated GPIO chips can also be defined in device-tree. The compatible string
+must be: "gpio-simulator". Supported properties are:
+
+ "gpio-sim,label" - chip label
+
+ "gpio-sim,nr-gpios" - number of lines
+
+Other standard GPIO properties (like "gpio-line-names" and gpio-hog) are also
+supported.
+
+Manipulating simulated lines
+----------------------------
+
+Each simulated GPIO chip creates a sysfs attribute group under its device
+directory called 'line-ctrl'. Inside each group, there's a separate attribute
+for each GPIO line. The name of the attribute is of the form 'gpioX' where X
+is the line's offset in the chip.
+
+Reading from a line attribute returns the current value. Writing to it (0 or 1)
+changes the configuration of the simulated pull-up/pull-down resistor
+(1 - pull-up, 0 - pull-down).
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index fae5141251e5..2631d60eb2eb 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1680,6 +1680,14 @@ config GPIO_VIRTIO
These virtual GPIOs can be routed to real GPIOs or attached to
simulators on the host (like QEMU).

+config GPIO_SIM
+ tristate "GPIO Simulator Module"
+ select IRQ_SIM
+ select CONFIGFS_FS
+ help
+ This enables the GPIO simulator - a configfs-based GPIO testing
+ driver.
+
endmenu

endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index fbcda637d5e1..1cb16c767237 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -133,6 +133,7 @@ obj-$(CONFIG_GPIO_SAMA5D2_PIOBU) += gpio-sama5d2-piobu.o
obj-$(CONFIG_GPIO_SCH311X) += gpio-sch311x.o
obj-$(CONFIG_GPIO_SCH) += gpio-sch.o
obj-$(CONFIG_GPIO_SIFIVE) += gpio-sifive.o
+obj-$(CONFIG_GPIO_SIM) += gpio-sim.o
obj-$(CONFIG_GPIO_SIOX) += gpio-siox.o
obj-$(CONFIG_GPIO_SL28CPLD) += gpio-sl28cpld.o
obj-$(CONFIG_GPIO_SODAVILLE) += gpio-sodaville.o
diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
new file mode 100644
index 000000000000..b21541c0b700
--- /dev/null
+++ b/drivers/gpio/gpio-sim.c
@@ -0,0 +1,877 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * GPIO testing driver based on configfs.
+ *
+ * Copyright (C) 2021 Bartosz Golaszewski <bgolaszewski@baylibre.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/configfs.h>
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/idr.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irq_sim.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/string_helpers.h>
+#include <linux/sysfs.h>
+
+#include "gpiolib.h"
+
+static DEFINE_IDA(gpio_sim_ida);
+
+struct gpio_sim_chip {
+ struct gpio_chip gc;
+ unsigned long *directions;
+ unsigned long *values;
+ unsigned long *pulls;
+ struct irq_domain *irq_sim;
+ struct mutex lock;
+ struct attribute_group attr_group;
+};
+
+struct gpio_sim_attribute {
+ struct device_attribute dev_attr;
+ unsigned int offset;
+};
+
+static struct gpio_sim_attribute *
+to_gpio_sim_attr(struct device_attribute *dev_attr)
+{
+ return container_of(dev_attr, struct gpio_sim_attribute, dev_attr);
+}
+
+static int gpio_sim_apply_pull(struct gpio_sim_chip *chip,
+ unsigned int offset, int value)
+{
+ int curr_val, irq, irq_type, ret;
+ struct gpio_desc *desc;
+ struct gpio_chip *gc;
+
+ gc = &chip->gc;
+ desc = &gc->gpiodev->descs[offset];
+
+ mutex_lock(&chip->lock);
+
+ if (test_bit(FLAG_REQUESTED, &desc->flags) &&
+ !test_bit(FLAG_IS_OUT, &desc->flags)) {
+ curr_val = !!test_bit(offset, chip->values);
+ if (curr_val == value)
+ goto set_pull;
+
+ /*
+ * This is fine - it just means, nobody is listening
+ * for interrupts on this line, otherwise
+ * irq_create_mapping() would have been called from
+ * the to_irq() callback.
+ */
+ irq = irq_find_mapping(chip->irq_sim, offset);
+ if (!irq)
+ goto set_value;
+
+ irq_type = irq_get_trigger_type(irq);
+
+ if ((value && (irq_type & IRQ_TYPE_EDGE_RISING)) ||
+ (!value && (irq_type & IRQ_TYPE_EDGE_FALLING))) {
+ ret = irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING,
+ true);
+ if (ret)
+ goto set_pull;
+ }
+ }
+
+set_value:
+ /* Change the value unless we're actively driving the line. */
+ if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
+ !test_bit(FLAG_IS_OUT, &desc->flags))
+ __assign_bit(offset, chip->values, value);
+
+set_pull:
+ __assign_bit(offset, chip->pulls, value);
+ mutex_unlock(&chip->lock);
+ return 0;
+}
+
+static int gpio_sim_get(struct gpio_chip *gc, unsigned int offset)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+ int ret;
+
+ mutex_lock(&chip->lock);
+ ret = !!test_bit(offset, chip->values);
+ mutex_unlock(&chip->lock);
+
+ return ret;
+}
+
+static void gpio_sim_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ mutex_lock(&chip->lock);
+ __assign_bit(offset, chip->values, value);
+ mutex_unlock(&chip->lock);
+}
+
+static int gpio_sim_get_multiple(struct gpio_chip *gc,
+ unsigned long *mask, unsigned long *bits)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ mutex_lock(&chip->lock);
+ bitmap_copy(bits, chip->values, gc->ngpio);
+ mutex_unlock(&chip->lock);
+
+ return 0;
+}
+
+static void gpio_sim_set_multiple(struct gpio_chip *gc,
+ unsigned long *mask, unsigned long *bits)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ mutex_lock(&chip->lock);
+ bitmap_copy(chip->values, bits, gc->ngpio);
+ mutex_unlock(&chip->lock);
+}
+
+static int gpio_sim_direction_output(struct gpio_chip *gc,
+ unsigned int offset, int value)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ mutex_lock(&chip->lock);
+ __clear_bit(offset, chip->directions);
+ __assign_bit(offset, chip->values, value);
+ mutex_unlock(&chip->lock);
+
+ return 0;
+}
+
+static int gpio_sim_direction_input(struct gpio_chip *gc, unsigned int offset)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ mutex_lock(&chip->lock);
+ __set_bit(offset, chip->directions);
+ mutex_unlock(&chip->lock);
+
+ return 0;
+}
+
+static int gpio_sim_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+ int direction;
+
+ mutex_lock(&chip->lock);
+ direction = !!test_bit(offset, chip->directions);
+ mutex_unlock(&chip->lock);
+
+ return direction ? GPIO_LINE_DIRECTION_IN : GPIO_LINE_DIRECTION_OUT;
+}
+
+static int gpio_sim_set_config(struct gpio_chip *gc,
+ unsigned int offset, unsigned long config)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ switch (pinconf_to_config_param(config)) {
+ case PIN_CONFIG_BIAS_PULL_UP:
+ return gpio_sim_apply_pull(chip, offset, 1);
+ case PIN_CONFIG_BIAS_PULL_DOWN:
+ return gpio_sim_apply_pull(chip, offset, 0);
+ default:
+ break;
+ }
+
+ return -ENOTSUPP;
+}
+
+static int gpio_sim_to_irq(struct gpio_chip *gc, unsigned int offset)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ return irq_create_mapping(chip->irq_sim, offset);
+}
+
+static void gpio_sim_free(struct gpio_chip *gc, unsigned int offset)
+{
+ struct gpio_sim_chip *chip = gpiochip_get_data(gc);
+
+ mutex_lock(&chip->lock);
+ __assign_bit(offset, chip->values, !!test_bit(offset, chip->pulls));
+ mutex_unlock(&chip->lock);
+}
+
+static ssize_t gpio_sim_sysfs_line_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
+ struct gpio_sim_chip *chip = dev_get_drvdata(dev);
+ int ret;
+
+ mutex_lock(&chip->lock);
+ ret = sysfs_emit(buf, "%u\n",
+ !!test_bit(line_attr->offset, chip->values));
+ mutex_unlock(&chip->lock);
+
+ return ret;
+}
+
+static ssize_t gpio_sim_sysfs_line_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
+ struct gpio_sim_chip *chip = dev_get_drvdata(dev);
+ int ret, val;
+
+ if (len > 2 || (buf[0] != '0' && buf[0] != '1'))
+ return -EINVAL;
+
+ val = buf[0] == '0' ? 0 : 1;
+
+ ret = gpio_sim_apply_pull(chip, line_attr->offset, val);
+ if (ret)
+ return ret;
+
+ return len;
+}
+
+static void gpio_sim_mutex_destroy(void *data)
+{
+ struct mutex *lock = data;
+
+ mutex_destroy(lock);
+}
+
+static void gpio_sim_sysfs_remove(void *data)
+{
+ struct gpio_sim_chip *chip = data;
+
+ sysfs_remove_group(&chip->gc.parent->kobj, &chip->attr_group);
+}
+
+static int gpio_sim_setup_sysfs(struct gpio_sim_chip *chip)
+{
+ unsigned int i, num_lines = chip->gc.ngpio;
+ struct device *dev = chip->gc.parent;
+ struct gpio_sim_attribute *line_attr;
+ struct device_attribute *dev_attr;
+ struct attribute **attrs;
+ int ret;
+
+ attrs = devm_kcalloc(dev, sizeof(*attrs), num_lines + 1, GFP_KERNEL);
+ if (!attrs)
+ return -ENOMEM;
+
+ for (i = 0; i < num_lines; i++) {
+ line_attr = devm_kzalloc(dev, sizeof(*line_attr), GFP_KERNEL);
+ if (!line_attr)
+ return -ENOMEM;
+
+ line_attr->offset = i;
+
+ dev_attr = &line_attr->dev_attr;
+ sysfs_attr_init(&dev_attr->attr);
+
+ dev_attr->attr.name = devm_kasprintf(dev, GFP_KERNEL,
+ "gpio%u", i);
+ if (!dev_attr->attr.name)
+ return -ENOMEM;
+
+ dev_attr->attr.mode = 0644;
+
+ dev_attr->show = gpio_sim_sysfs_line_show;
+ dev_attr->store = gpio_sim_sysfs_line_store;
+
+ attrs[i] = &dev_attr->attr;
+ }
+
+ chip->attr_group.name = "line-ctrl";
+ chip->attr_group.attrs = attrs;
+
+ ret = sysfs_create_group(&dev->kobj, &chip->attr_group);
+ if (ret)
+ return ret;
+
+ return devm_add_action_or_reset(dev, gpio_sim_sysfs_remove, chip);
+}
+
+static int gpio_sim_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct gpio_sim_chip *chip;
+ struct gpio_chip *gc;
+ const char *label;
+ u32 num_lines;
+ int ret;
+
+ ret = device_property_read_u32(dev, "gpio-sim,nr-gpios", &num_lines);
+ if (ret)
+ return ret;
+
+ ret = device_property_read_string(dev, "gpio-sim,label", &label);
+ if (ret)
+ label = dev_name(dev);
+
+ chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
+ if (!chip)
+ return -ENOMEM;
+
+ chip->directions = devm_bitmap_alloc(dev, num_lines, GFP_KERNEL);
+ if (!chip->directions)
+ return -ENOMEM;
+
+ /* Default to input mode. */
+ bitmap_fill(chip->directions, num_lines);
+
+ chip->values = devm_bitmap_zalloc(dev, num_lines, GFP_KERNEL);
+ if (!chip->values)
+ return -ENOMEM;
+
+ chip->pulls = devm_bitmap_zalloc(dev, num_lines, GFP_KERNEL);
+ if (!chip->pulls)
+ return -ENOMEM;
+
+ chip->irq_sim = devm_irq_domain_create_sim(dev, NULL, num_lines);
+ if (IS_ERR(chip->irq_sim))
+ return PTR_ERR(chip->irq_sim);
+
+ mutex_init(&chip->lock);
+ ret = devm_add_action_or_reset(dev, gpio_sim_mutex_destroy,
+ &chip->lock);
+ if (ret)
+ return ret;
+
+ gc = &chip->gc;
+ gc->base = -1;
+ gc->ngpio = num_lines;
+ gc->label = label;
+ gc->owner = THIS_MODULE;
+ gc->parent = dev;
+ gc->get = gpio_sim_get;
+ gc->set = gpio_sim_set;
+ gc->get_multiple = gpio_sim_get_multiple;
+ gc->set_multiple = gpio_sim_set_multiple;
+ gc->direction_output = gpio_sim_direction_output;
+ gc->direction_input = gpio_sim_direction_input;
+ gc->get_direction = gpio_sim_get_direction;
+ gc->set_config = gpio_sim_set_config;
+ gc->to_irq = gpio_sim_to_irq;
+ gc->free = gpio_sim_free;
+
+ ret = devm_gpiochip_add_data(dev, gc, chip);
+ if (ret)
+ return ret;
+
+ /* Used by sysfs and configfs callbacks. */
+ dev_set_drvdata(dev, chip);
+
+ ret = gpio_sim_setup_sysfs(chip);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+static const struct of_device_id gpio_sim_of_match[] = {
+ { .compatible = "gpio-simulator" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, gpio_sim_of_match);
+
+static struct platform_driver gpio_sim_driver = {
+ .driver = {
+ .name = "gpio-sim",
+ .of_match_table = gpio_sim_of_match,
+ },
+ .probe = gpio_sim_probe,
+};
+
+struct gpio_sim_chip_config {
+ struct config_item item;
+
+ /*
+ * If pdev is NULL, the item is 'pending' (waiting for configuration).
+ * Once the pointer is assigned, the device has been created and the
+ * item is 'live'.
+ */
+ struct platform_device *pdev;
+ int id;
+
+ /*
+ * Each configfs filesystem operation is protected with the subsystem
+ * mutex. Each separate attribute is protected with the buffer mutex.
+ * This structure however can be modified by callbacks of different
+ * attributes so we need another lock.
+ */
+ struct mutex lock;
+
+ char label[32];
+ unsigned int num_lines;
+ char **line_names;
+ unsigned int num_line_names;
+};
+
+static struct gpio_sim_chip_config *
+to_gpio_sim_chip_config(struct config_item *item)
+{
+ return container_of(item, struct gpio_sim_chip_config, item);
+}
+
+static ssize_t gpio_sim_config_dev_name_show(struct config_item *item,
+ char *page)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ struct platform_device *pdev;
+ int ret;
+
+ mutex_lock(&config->lock);
+ pdev = config->pdev;
+ if (pdev)
+ ret = sprintf(page, "%s\n", dev_name(&pdev->dev));
+ else
+ ret = sprintf(page, "gpio-sim.%d\n", config->id);
+ mutex_unlock(&config->lock);
+
+ return ret;
+}
+
+CONFIGFS_ATTR_RO(gpio_sim_config_, dev_name);
+
+static ssize_t gpio_sim_config_chip_name_show(struct config_item *item,
+ char *page)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ struct gpio_sim_chip *chip = NULL;
+ struct platform_device *pdev;
+ int ret;
+
+ mutex_lock(&config->lock);
+ pdev = config->pdev;
+ if (pdev)
+ chip = dev_get_drvdata(&pdev->dev);
+
+ if (chip)
+ ret = sprintf(page, "%s\n", dev_name(&chip->gc.gpiodev->dev));
+ else
+ ret = sprintf(page, "none\n");
+ mutex_unlock(&config->lock);
+
+ return ret;
+}
+
+CONFIGFS_ATTR_RO(gpio_sim_config_, chip_name);
+
+static ssize_t gpio_sim_config_label_show(struct config_item *item, char *page)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ int ret;
+
+ mutex_lock(&config->lock);
+ ret = sprintf(page, "%s\n", config->label);
+ mutex_unlock(&config->lock);
+
+ return ret;
+}
+
+static ssize_t gpio_sim_config_label_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ char *dup, *trimmed;
+ int ret;
+
+ mutex_lock(&config->lock);
+
+ if (config->pdev) {
+ mutex_unlock(&config->lock);
+ return -EBUSY;
+ }
+
+ dup = kstrndup(page, count, GFP_KERNEL);
+ if (!dup) {
+ mutex_unlock(&config->lock);
+ return -ENOMEM;
+ }
+
+ trimmed = strstrip(dup);
+ ret = snprintf(config->label, sizeof(config->label), "%s", trimmed);
+ kfree(dup);
+ if (ret < 0) {
+ mutex_unlock(&config->lock);
+ return ret;
+ }
+
+ mutex_unlock(&config->lock);
+ return count;
+}
+
+CONFIGFS_ATTR(gpio_sim_config_, label);
+
+static ssize_t gpio_sim_config_num_lines_show(struct config_item *item,
+ char *page)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ int ret;
+
+ mutex_lock(&config->lock);
+ ret = sprintf(page, "%u\n", config->num_lines);
+ mutex_unlock(&config->lock);
+
+ return ret;
+}
+
+static ssize_t gpio_sim_config_num_lines_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ unsigned int num_lines;
+ int ret;
+
+ mutex_lock(&config->lock);
+
+ if (config->pdev) {
+ mutex_unlock(&config->lock);
+ return -EBUSY;
+ }
+
+ ret = kstrtouint(page, 10, &num_lines);
+ if (ret) {
+ mutex_unlock(&config->lock);
+ return ret;
+ }
+
+ if (num_lines == 0) {
+ mutex_unlock(&config->lock);
+ return -EINVAL;
+ }
+
+ config->num_lines = num_lines;
+
+ mutex_unlock(&config->lock);
+ return count;
+}
+
+CONFIGFS_ATTR(gpio_sim_config_, num_lines);
+
+static ssize_t gpio_sim_config_line_names_show(struct config_item *item,
+ char *page)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ int ret, i, written = 0;
+
+ mutex_lock(&config->lock);
+
+ if (!config->line_names) {
+ mutex_unlock(&config->lock);
+ return sprintf(page, "\n");
+ }
+
+ for (i = 0; i < config->num_line_names; i++) {
+ ret = sprintf(page + written,
+ i < config->num_line_names - 1 ? "\"%s\", " : "\"%s\"\n",
+ config->line_names[i] ?: "");
+ if (ret < 0) {
+ mutex_unlock(&config->lock);
+ return ret;
+ }
+
+ written += ret;
+ }
+
+ mutex_unlock(&config->lock);
+ return written;
+}
+
+static ssize_t gpio_sim_config_line_names_store(struct config_item *item,
+ const char *page, size_t count)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ unsigned int num_new_names = 1, num_old_names, name_idx = 0;
+ bool in_quote = false, got_comma = true;
+ char **new_names, **old_names, *name, c;
+ const char *start = page;
+ size_t pos, name_len;
+ int err = -EINVAL;
+
+ mutex_lock(&config->lock);
+
+ if (config->pdev) {
+ mutex_unlock(&config->lock);
+ return -EBUSY;
+ }
+
+ /*
+ * Line names are stored in a pointer array so that we can easily
+ * pass them down to the GPIO subsystem in a "gpio-line-names"
+ * property.
+ *
+ * Line names must be passed as a list of quoted names separated by
+ * commas, for example: '"foo", "bar", "foobar"'.
+ */
+
+ for (pos = 0; pos < count; pos++) {
+ /*
+ * Just count the commas and assume the number if strings
+ * equals the number of commas + 1. If the format is wrong
+ * we'll bail out anyway.
+ */
+ if (page[pos] == ',')
+ num_new_names++;
+ }
+
+ new_names = kcalloc(num_new_names, sizeof(char *), GFP_KERNEL);
+ if (!new_names) {
+ mutex_unlock(&config->lock);
+ return -ENOMEM;
+ }
+
+ /*
+ * REVISIT There are more users in the kernel that want to split
+ * comma-separated strings into tokens. We should generalize it and
+ * put it into lib/.
+ */
+ for (pos = 0; pos < count; pos++) {
+ c = page[pos];
+
+ if (in_quote) {
+ if (c == '"') {
+ /* This is the end of the name. */
+ in_quote = got_comma = false;
+ name_len = (page + pos) - start;
+ if (name_len == 0) {
+ /* Name is empty (passed as ""). */
+ name_idx++;
+ continue;
+ }
+
+ name = kmemdup(start, name_len + 1, GFP_KERNEL);
+ if (!name) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+
+ name[name_len] = '\0';
+ new_names[name_idx++] = name;
+ }
+ } else {
+ if (c == '"') {
+ /* Enforce separating names with commas. */
+ if (!got_comma)
+ goto err_out;
+
+ start = page + pos + 1;
+ in_quote = true;
+ } else if (c == ',') {
+ if (!got_comma)
+ got_comma = true;
+ else
+ /* Double commas are not allowed. */
+ goto err_out;
+ } else if (!isspace(c)) {
+ goto err_out;
+ }
+ }
+ }
+
+ /*
+ * End of input sanity checks, must not have a comma at the end and
+ * must have finished scanning the last name.
+ */
+ if (in_quote || got_comma)
+ goto err_out;
+
+ old_names = config->line_names;
+ num_old_names = config->num_line_names;
+ config->line_names = new_names;
+ config->num_line_names = num_new_names;
+
+ mutex_unlock(&config->lock);
+ kfree_strarray(old_names, num_old_names);
+ return count;
+
+err_out:
+ mutex_unlock(&config->lock);
+ kfree_strarray(new_names, name_idx);
+ return err;
+}
+
+CONFIGFS_ATTR(gpio_sim_config_, line_names);
+
+static struct configfs_attribute *gpio_sim_config_attrs[] = {
+ &gpio_sim_config_attr_dev_name,
+ &gpio_sim_config_attr_chip_name,
+ &gpio_sim_config_attr_label,
+ &gpio_sim_config_attr_num_lines,
+ &gpio_sim_config_attr_line_names,
+ NULL
+};
+
+static void gpio_sim_chip_config_release(struct config_item *item)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+
+ mutex_destroy(&config->lock);
+ ida_free(&gpio_sim_ida, config->id);
+ kfree_strarray(config->line_names, config->num_line_names);
+ kfree(config);
+}
+
+static struct configfs_item_operations gpio_sim_config_item_ops = {
+ .release = gpio_sim_chip_config_release,
+};
+
+static const struct config_item_type gpio_sim_chip_config_type = {
+ .ct_item_ops = &gpio_sim_config_item_ops,
+ .ct_attrs = gpio_sim_config_attrs,
+ .ct_owner = THIS_MODULE,
+};
+
+static struct config_item *
+gpio_sim_config_make_item(struct config_group *group, const char *name)
+{
+ struct gpio_sim_chip_config *config;
+ int id;
+
+ config = kzalloc(sizeof(*config), GFP_KERNEL);
+ if (!config)
+ return ERR_PTR(-ENOMEM);
+
+ id = ida_alloc(&gpio_sim_ida, GFP_KERNEL);
+ if (id < 0) {
+ kfree(config);
+ return ERR_PTR(id);
+ }
+
+ config_item_init_type_name(&config->item, name,
+ &gpio_sim_chip_config_type);
+ config->num_lines = 1;
+ config->id = id;
+ mutex_init(&config->lock);
+
+ return &config->item;
+}
+
+static int gpio_sim_config_commit_item(struct config_item *item)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+ struct platform_device_info pdevinfo;
+ struct property_entry properties[4]; /* Max 3 properties + sentinel. */
+ struct platform_device *pdev;
+ unsigned int prop_idx = 0;
+
+ memset(&pdevinfo, 0, sizeof(pdevinfo));
+ memset(properties, 0, sizeof(properties));
+
+ mutex_lock(&config->lock);
+
+ properties[prop_idx++] = PROPERTY_ENTRY_U32("gpio-sim,nr-gpios",
+ config->num_lines);
+
+ if (config->label[0] != '\0')
+ properties[prop_idx++] = PROPERTY_ENTRY_STRING("gpio-sim,label",
+ config->label);
+
+ if (config->line_names)
+ properties[prop_idx++] = PROPERTY_ENTRY_STRING_ARRAY_LEN(
+ "gpio-line-names",
+ config->line_names,
+ config->num_line_names);
+
+ pdevinfo.name = "gpio-sim";
+ pdevinfo.properties = properties;
+ pdevinfo.id = config->id;
+
+ pdev = platform_device_register_full(&pdevinfo);
+ if (IS_ERR(pdev)) {
+ mutex_unlock(&config->lock);
+ return PTR_ERR(pdev);
+ }
+
+ config->pdev = pdev;
+ mutex_unlock(&config->lock);
+
+ return 0;
+}
+
+static int gpio_sim_config_uncommit_item(struct config_item *item)
+{
+ struct gpio_sim_chip_config *config = to_gpio_sim_chip_config(item);
+
+ mutex_lock(&config->lock);
+ platform_device_unregister(config->pdev);
+ config->pdev = NULL;
+ mutex_unlock(&config->lock);
+
+ return 0;
+}
+
+static struct configfs_group_operations gpio_sim_config_group_ops = {
+ .make_item = gpio_sim_config_make_item,
+ .commit_item = gpio_sim_config_commit_item,
+ .uncommit_item = gpio_sim_config_uncommit_item,
+};
+
+static const struct config_item_type gpio_sim_config_type = {
+ .ct_group_ops = &gpio_sim_config_group_ops,
+ .ct_owner = THIS_MODULE,
+};
+
+static struct configfs_subsystem gpio_sim_config_subsys = {
+ .su_group = {
+ .cg_item = {
+ .ci_namebuf = "gpio-sim",
+ .ci_type = &gpio_sim_config_type,
+ },
+ },
+};
+
+static int __init gpio_sim_init(void)
+{
+ int ret;
+
+ ret = platform_driver_register(&gpio_sim_driver);
+ if (ret) {
+ pr_err("Error %d while registering the platform driver\n", ret);
+ return ret;
+ }
+
+ config_group_init(&gpio_sim_config_subsys.su_group);
+ mutex_init(&gpio_sim_config_subsys.su_mutex);
+ ret = configfs_register_subsystem(&gpio_sim_config_subsys);
+ if (ret) {
+ pr_err("Error %d while registering the configfs subsystem %s\n",
+ ret, gpio_sim_config_subsys.su_group.cg_item.ci_namebuf);
+ mutex_destroy(&gpio_sim_config_subsys.su_mutex);
+ platform_driver_unregister(&gpio_sim_driver);
+ return ret;
+ }
+
+ return 0;
+}
+module_init(gpio_sim_init);
+
+static void __exit gpio_sim_exit(void)
+{
+ configfs_unregister_subsystem(&gpio_sim_config_subsys);
+ mutex_destroy(&gpio_sim_config_subsys.su_mutex);
+ platform_driver_unregister(&gpio_sim_driver);
+}
+module_exit(gpio_sim_exit);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bgolaszewski@baylibre.com>");
+MODULE_DESCRIPTION("GPIO Simulator Module");
+MODULE_LICENSE("GPL");
--
2.30.1