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    Subject[PATCH v11 3/6] gpio: sim: new testing module
    Date
    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>
    ---
    Documentation/admin-guide/gpio/gpio-sim.rst | 93 ++
    drivers/gpio/Kconfig | 8 +
    drivers/gpio/Makefile | 1 +
    drivers/gpio/gpio-sim.c | 1592 +++++++++++++++++++
    4 files changed, 1694 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..ec28e9ac9b9c
    --- /dev/null
    +++ b/Documentation/admin-guide/gpio/gpio-sim.rst
    @@ -0,0 +1,93 @@
    +.. 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'. For
    +details of the configfs filesystem, please refer to the configfs documentaion.
    +
    +The user can create a hierarchy of configfs groups and items as well as modify
    +values of exposed attributes. Once the chip is instantiated, this hierarchy
    +will be translated to appropriate device properties. The general structure is:
    +
    +Group: /config/gpio-sim
    +
    +This is the top directory of the gpio-sim configfs tree.
    +
    +Group: /config/gpio-sim/gpio-device
    +Attribute: /config/gpio-sim/gpio-device/dev_name
    +Attribute: /config/gpio-sim/gpio-device/live
    +
    +This is a directory representing a GPIO platform device. The 'dev_name'
    +attribute is read-only and allows the user-space to read the platform device
    +name (e.g. 'gpio-sim.0'). The 'live' attribute allows to trigger the actual
    +creation of the device once it's fully configured. The accepted values are:
    +'1' to enable the simulated device and '0' to disable and tear it down.
    +
    +Group: /config/gpio-sim/gpio-device/gpio-bankX/
    +Attribute: /config/gpio-sim/gpio-device/gpio-bankX/chip_name
    +Attribute: /config/gpio-sim/gpio-device/gpio-bankX/num_lines
    +
    +This group represents a bank of GPIOs under the top platform device. The
    +'chip_name' attribute is read-only and allows the user-space to read the
    +device name of the bank device. The 'num_lines' attribute allows to specify
    +the number of lines exposed by this bank.
    +
    +Group: /config/gpio-sim/gpio-device/gpio-bankX/lineY
    +Attribute: /config/gpio-sim/gpio-device/gpio-bankX/lineY/name
    +
    +This group represents a single line at the offset Y. The 'name' attribute
    +allows to set the line name as represented by the 'gpio-line-names' property.
    +
    +Item: /config/gpio-sim/gpio-device/gpio-bankX/lineY/hog
    +Attribute: /config/gpio-sim/gpio-device/gpio-bankX/lineY/hog/name
    +Attribute: /config/gpio-sim/gpio-device/gpio-bankX/lineY/hog/direction
    +
    +This item makes the gpio-sim module hog the associated line. The 'name'
    +attribute specifies the in-kernel consumer name to use. The 'direction'
    +attribute specifies the hog direction and must be one of: 'input',
    +'output-high' and 'output-low'.
    +
    +Inside each bank directory, there's a set of attributes that can be used to
    +configure the new chip. Additionally the user can mkdir() subdirectories inside
    +the chip's directory that allow to pass additional configuration for specific
    +lines. The name of those subdirectories must take the form of: 'line<offset>'
    +(e.g. 'line0', 'line20', etc.) as the name will be used by the module to assign
    +the config to the specific line at given offset.
    +
    +Once the confiuration is complete, the 'live' attribute must be set to 1 in
    +order to instantiate the chip. It can be set back to 0 to destroy the simulated
    +chip. The module will synchronously wait for the new simulated device to be
    +successfully probed and if this doesn't happen, writing to 'live' will result
    +in an error.
    +
    +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
    +
    +Other standard GPIO properties (like "gpio-line-names", "ngpios" or gpio-hog)
    +are also supported.
    +
    +Manipulating simulated lines
    +----------------------------
    +
    +Each simulated GPIO chip creates a separate sysfs group under its device
    +directory for each exposed line
    +(e.g. /sys/devices/platform/gpio-sim.X/gpiochipY/). The name of each group
    +is of the form: 'sim_gpioX' where X is the offset of the line. Inside each
    +group there are two attibutes:
    +
    + pull - allows to read and set the current simulated pull setting for every
    + line, when writing the value must be one of: 'pull-up', 'pull-down'
    +
    + value - allows to read the current value of the line which may be different
    + from the pull if the line is being driven from user-space
    diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
    index 60d9374c72c0..9acdb4d1047b 100644
    --- a/drivers/gpio/Kconfig
    +++ b/drivers/gpio/Kconfig
    @@ -1694,6 +1694,14 @@ 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 71ee9fc2ff83..f21577de2474 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..0785b1b9053f
    --- /dev/null
    +++ b/drivers/gpio/gpio-sim.c
    @@ -0,0 +1,1592 @@
    +// SPDX-License-Identifier: GPL-2.0-or-later
    +/*
    + * GPIO testing driver based on configfs.
    + *
    + * Copyright (C) 2021 Bartosz Golaszewski <brgl@bgdev.pl>
    + */
    +
    +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
    +
    +#include <linux/bitmap.h>
    +#include <linux/completion.h>
    +#include <linux/configfs.h>
    +#include <linux/device.h>
    +#include <linux/gpio/driver.h>
    +#include <linux/gpio/machine.h>
    +#include <linux/idr.h>
    +#include <linux/interrupt.h>
    +#include <linux/irq.h>
    +#include <linux/irq_sim.h>
    +#include <linux/list.h>
    +#include <linux/mod_devicetable.h>
    +#include <linux/module.h>
    +#include <linux/mutex.h>
    +#include <linux/notifier.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"
    +
    +#define GPIO_SIM_PROP_MAX 4 /* Max 3 properties + sentinel. */
    +#define GPIO_SIM_NUM_ATTRS 3 /* value, pull and sentinel */
    +
    +static DEFINE_IDA(gpio_sim_ida);
    +
    +struct gpio_sim_chip {
    + struct gpio_chip gc;
    + unsigned long *direction_map;
    + unsigned long *value_map;
    + unsigned long *pull_map;
    + struct irq_domain *irq_sim;
    + struct mutex lock;
    + const struct attribute_group **attr_groups;
    +};
    +
    +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->value_map);
    + 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->value_map, value);
    +
    +set_pull:
    + __assign_bit(offset, chip->pull_map, 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->value_map);
    + 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->value_map, 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->value_map, 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->value_map, 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->direction_map);
    + __assign_bit(offset, chip->value_map, 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->direction_map);
    + 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->direction_map);
    + 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->value_map, !!test_bit(offset, chip->pull_map));
    + mutex_unlock(&chip->lock);
    +}
    +
    +static ssize_t gpio_sim_sysfs_val_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 val;
    +
    + mutex_lock(&chip->lock);
    + val = !!test_bit(line_attr->offset, chip->value_map);
    + mutex_unlock(&chip->lock);
    +
    + return sysfs_emit(buf, "%d\n", val);
    +}
    +
    +static ssize_t gpio_sim_sysfs_val_store(struct device *dev,
    + struct device_attribute *attr,
    + const char *buf, size_t count)
    +{
    + /*
    + * Not assigning this function will result in write() returning -EIO
    + * which is confusing. Return -EPERM explicitly.
    + */
    + return -EPERM;
    +}
    +
    +static ssize_t gpio_sim_sysfs_pull_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);
    + char *repr;
    + int pull;
    +
    + mutex_lock(&chip->lock);
    + pull = !!test_bit(line_attr->offset, chip->pull_map);
    + mutex_unlock(&chip->lock);
    +
    + if (pull)
    + repr = "pull-up";
    + else
    + repr = "pull-down";
    +
    + return sysfs_emit(buf, "%s\n", repr);
    +}
    +
    +static ssize_t gpio_sim_sysfs_pull_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, pull;
    +
    + if (sysfs_streq(buf, "pull-down"))
    + pull = 0;
    + else if (sysfs_streq(buf, "pull-up"))
    + pull = 1;
    + else
    + return -EINVAL;
    +
    + ret = gpio_sim_apply_pull(chip, line_attr->offset, pull);
    + 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_groups(&chip->gc.gpiodev->dev.kobj, chip->attr_groups);
    +}
    +
    +static int gpio_sim_setup_sysfs(struct gpio_sim_chip *chip)
    +{
    + struct device_attribute *val_dev_attr, *pull_dev_attr;
    + struct gpio_sim_attribute *val_attr, *pull_attr;
    + unsigned int num_lines = chip->gc.ngpio;
    + struct device *dev = chip->gc.parent;
    + struct attribute_group *attr_group;
    + struct attribute **attrs;
    + int i, ret;
    +
    + chip->attr_groups = devm_kcalloc(dev, sizeof(*chip->attr_groups),
    + num_lines + 1, GFP_KERNEL);
    + if (!chip->attr_groups)
    + return -ENOMEM;
    +
    + for (i = 0; i < num_lines; i++) {
    + attr_group = devm_kzalloc(dev, sizeof(*attr_group), GFP_KERNEL);
    + attrs = devm_kcalloc(dev, sizeof(*attrs),
    + GPIO_SIM_NUM_ATTRS, GFP_KERNEL);
    + val_attr = devm_kzalloc(dev, sizeof(*val_attr), GFP_KERNEL);
    + pull_attr = devm_kzalloc(dev, sizeof(*pull_attr), GFP_KERNEL);
    + if (!attr_group || !attrs || !val_attr || !pull_attr)
    + return -ENOMEM;
    +
    + attr_group->name = devm_kasprintf(dev, GFP_KERNEL,
    + "sim_gpio%u", i);
    + if (!attr_group->name)
    + return -ENOMEM;
    +
    + val_attr->offset = pull_attr->offset = i;
    +
    + val_dev_attr = &val_attr->dev_attr;
    + pull_dev_attr = &pull_attr->dev_attr;
    +
    + sysfs_attr_init(&val_dev_attr->attr);
    + sysfs_attr_init(&pull_dev_attr->attr);
    +
    + val_dev_attr->attr.name = "value";
    + pull_dev_attr->attr.name = "pull";
    +
    + val_dev_attr->attr.mode = pull_dev_attr->attr.mode = 0644;
    +
    + val_dev_attr->show = gpio_sim_sysfs_val_show;
    + val_dev_attr->store = gpio_sim_sysfs_val_store;
    + pull_dev_attr->show = gpio_sim_sysfs_pull_show;
    + pull_dev_attr->store = gpio_sim_sysfs_pull_store;
    +
    + attrs[0] = &val_dev_attr->attr;
    + attrs[1] = &pull_dev_attr->attr;
    +
    + attr_group->attrs = attrs;
    + chip->attr_groups[i] = attr_group;
    + }
    +
    + ret = sysfs_create_groups(&chip->gc.gpiodev->dev.kobj,
    + chip->attr_groups);
    + if (ret)
    + return ret;
    +
    + return devm_add_action_or_reset(dev, gpio_sim_sysfs_remove, chip);
    +}
    +
    +static int gpio_sim_add_bank(struct fwnode_handle *swnode, struct device *dev)
    +{
    + struct gpio_sim_chip *chip;
    + struct gpio_chip *gc;
    + const char *label;
    + u32 num_lines;
    + int ret;
    +
    + ret = fwnode_property_read_u32(swnode, "ngpios", &num_lines);
    + if (ret)
    + return ret;
    +
    + ret = fwnode_property_read_string(swnode, "gpio-sim,label", &label);
    + if (ret) {
    + label = devm_kasprintf(dev, GFP_KERNEL, "%s-%s",
    + dev_name(dev), fwnode_get_name(swnode));
    + if (!label)
    + return -ENOMEM;
    + }
    +
    + chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
    + if (!chip)
    + return -ENOMEM;
    +
    + chip->direction_map = devm_bitmap_alloc(dev, num_lines, GFP_KERNEL);
    + if (!chip->direction_map)
    + return -ENOMEM;
    +
    + /* Default to input mode. */
    + bitmap_fill(chip->direction_map, num_lines);
    +
    + chip->value_map = devm_bitmap_zalloc(dev, num_lines, GFP_KERNEL);
    + if (!chip->value_map)
    + return -ENOMEM;
    +
    + chip->pull_map = devm_bitmap_zalloc(dev, num_lines, GFP_KERNEL);
    + if (!chip->pull_map)
    + 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->fwnode = swnode;
    + 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(&gc->gpiodev->dev, chip);
    +
    + return gpio_sim_setup_sysfs(chip);
    +}
    +
    +static int gpio_sim_probe(struct platform_device *pdev)
    +{
    + struct device *dev = &pdev->dev;
    + struct fwnode_handle *swnode;
    + int ret;
    +
    + device_for_each_child_node(dev, swnode) {
    + ret = gpio_sim_add_bank(swnode, dev);
    + 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_device {
    + struct config_group group;
    +
    + /*
    + * If pdev is NULL, the device 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.
    + *
    + * We use this lock fo protecting all data structures owned by this
    + * object too.
    + */
    + struct mutex lock;
    +
    + /*
    + * This is used to synchronously wait for the driver's probe to complete
    + * and notify the user-space about any errors.
    + */
    + struct notifier_block bus_notifier;
    + struct completion probe_completion;
    + bool driver_bound;
    +
    + struct gpiod_hog *hogs;
    +
    + struct list_head bank_list;
    +};
    +
    +/* This is called with dev->lock already taken. */
    +static int gpio_sim_bus_notifier_call(struct notifier_block *nb,
    + unsigned long action, void *data)
    +{
    + struct gpio_sim_device *simdev = container_of(nb,
    + struct gpio_sim_device,
    + bus_notifier);
    + struct device *dev = data;
    + char devname[32];
    +
    + snprintf(devname, sizeof(devname), "gpio-sim.%u", simdev->id);
    +
    + if (strcmp(dev_name(dev), devname) == 0) {
    + if (action == BUS_NOTIFY_BOUND_DRIVER)
    + simdev->driver_bound = true;
    + else if (action == BUS_NOTIFY_DRIVER_NOT_BOUND)
    + simdev->driver_bound = false;
    + else
    + return NOTIFY_DONE;
    +
    + complete(&simdev->probe_completion);
    + return NOTIFY_OK;
    + }
    +
    + return NOTIFY_DONE;
    +}
    +
    +static struct gpio_sim_device *to_gpio_sim_device(struct config_item *item)
    +{
    + struct config_group *group = to_config_group(item);
    +
    + return container_of(group, struct gpio_sim_device, group);
    +}
    +
    +struct gpio_sim_bank {
    + struct config_group group;
    +
    + /*
    + * We could have used the ci_parent field of the config_item but
    + * configfs is stupid and calls the item's release callback after
    + * already having cleared the parent pointer even though the parent
    + * is guaranteed to survive the child...
    + *
    + * So we need to store the pointer to the parent struct here. We can
    + * dereference it anywhere we need with no checks and no locking as
    + * it's guaranteed to survive the childred and protected by configfs
    + * locks.
    + *
    + * Same for other structures.
    + */
    + struct gpio_sim_device *parent;
    + struct list_head siblings;
    +
    + char *label;
    + unsigned int num_lines;
    +
    + struct list_head line_list;
    +
    + struct fwnode_handle *swnode;
    +};
    +
    +static struct gpio_sim_bank *to_gpio_sim_bank(struct config_item *item)
    +{
    + struct config_group *group = to_config_group(item);
    + return container_of(group, struct gpio_sim_bank, group);
    +}
    +
    +static struct gpio_sim_device *
    +gpio_sim_bank_get_device(struct gpio_sim_bank *bank)
    +{
    + return bank->parent;
    +}
    +
    +struct gpio_sim_hog;
    +
    +struct gpio_sim_line {
    + struct config_group group;
    +
    + struct gpio_sim_bank *parent;
    + struct list_head siblings;
    +
    + unsigned int offset;
    + char *name;
    +
    + /* There can only be one hog per line. */
    + struct gpio_sim_hog *hog;
    +};
    +
    +static struct gpio_sim_line *to_gpio_sim_line(struct config_item *item)
    +{
    + struct config_group *group = to_config_group(item);
    + return container_of(group, struct gpio_sim_line, group);
    +}
    +
    +static struct gpio_sim_device *
    +gpio_sim_line_get_device(struct gpio_sim_line *line)
    +{
    + struct gpio_sim_bank *bank = line->parent;
    +
    + return gpio_sim_bank_get_device(bank);
    +}
    +
    +struct gpio_sim_hog {
    + struct config_item item;
    + struct gpio_sim_line *parent;
    +
    + char *name;
    + int dir;
    +};
    +
    +static struct gpio_sim_hog *to_gpio_sim_hog(struct config_item *item)
    +{
    + return container_of(item, struct gpio_sim_hog, item);
    +}
    +
    +static struct gpio_sim_device *gpio_sim_hog_get_device(struct gpio_sim_hog *hog)
    +{
    + struct gpio_sim_line *line = hog->parent;
    +
    + return gpio_sim_line_get_device(line);
    +}
    +
    +static bool gpio_sim_device_is_live_unlocked(struct gpio_sim_device *dev)
    +{
    + return !!dev->pdev;
    +}
    +
    +static char *gpio_sim_strdup_trimmed(const char *str, size_t count)
    +{
    + char *dup, *trimmed, *ret;
    +
    + dup = kstrndup(str, count, GFP_KERNEL);
    + if (!dup)
    + return NULL;
    +
    + trimmed = strstrip(dup);
    + ret = kstrdup(trimmed, GFP_KERNEL);
    + kfree(dup);
    + return ret;
    +}
    +
    +static ssize_t gpio_sim_device_config_dev_name_show(struct config_item *item,
    + char *page)
    +{
    + struct gpio_sim_device *dev = to_gpio_sim_device(item);
    + struct platform_device *pdev;
    + int ret;
    +
    + mutex_lock(&dev->lock);
    + pdev = dev->pdev;
    + if (pdev)
    + ret = sprintf(page, "%s\n", dev_name(&pdev->dev));
    + else
    + ret = sprintf(page, "gpio-sim.%d\n", dev->id);
    + mutex_unlock(&dev->lock);
    +
    + return ret;
    +}
    +
    +CONFIGFS_ATTR_RO(gpio_sim_device_config_, dev_name);
    +
    +static ssize_t
    +gpio_sim_device_config_live_show(struct config_item *item, char *page)
    +{
    + struct gpio_sim_device *dev = to_gpio_sim_device(item);
    + bool live;
    +
    + mutex_lock(&dev->lock);
    + live = gpio_sim_device_is_live_unlocked(dev);
    + mutex_unlock(&dev->lock);
    +
    + return sprintf(page, "%c\n", live ? '1' : '0');
    +}
    +
    +static char **gpio_sim_make_line_names(struct gpio_sim_bank *bank,
    + unsigned int *line_names_size)
    +{
    + unsigned int max_offset = 0;
    + bool has_line_names = false;
    + struct gpio_sim_line *line;
    + char **line_names;
    +
    + list_for_each_entry(line, &bank->line_list, siblings) {
    + if (line->name) {
    + if (line->offset > max_offset)
    + max_offset = line->offset;
    +
    + /*
    + * max_offset can stay at 0 so it's not an indicator
    + * of whether line names were configured at all.
    + */
    + has_line_names = true;
    + }
    + }
    +
    + if (!has_line_names)
    + /*
    + * This is not an error - NULL means, there are no line
    + * names configured.
    + */
    + return NULL;
    +
    + *line_names_size = max_offset + 1;
    +
    + line_names = kcalloc(*line_names_size, sizeof(*line_names), GFP_KERNEL);
    + if (!line_names)
    + return ERR_PTR(-ENOMEM);
    +
    + list_for_each_entry(line, &bank->line_list, siblings)
    + line_names[line->offset] = line->name;
    +
    + return line_names;
    +}
    +
    +static void gpio_sim_remove_hogs(struct gpio_sim_device *dev)
    +{
    + struct gpiod_hog *hog;
    +
    + if (!dev->hogs)
    + return;
    +
    + gpiod_remove_hogs(dev->hogs);
    +
    + for (hog = dev->hogs; !hog->chip_label; hog++) {
    + kfree(hog->chip_label);
    + kfree(hog->line_name);
    + }
    +
    + kfree(dev->hogs);
    + dev->hogs = NULL;
    +}
    +
    +static int gpio_sim_add_hogs(struct gpio_sim_device *dev)
    +{
    + unsigned int num_hogs = 0, idx = 0;
    + struct gpio_sim_bank *bank;
    + struct gpio_sim_line *line;
    + struct gpiod_hog *hog;
    +
    + list_for_each_entry(bank, &dev->bank_list, siblings) {
    + list_for_each_entry(line, &bank->line_list, siblings) {
    + if (line->hog)
    + num_hogs++;
    + }
    + }
    +
    + if (!num_hogs)
    + return 0;
    +
    + /* Allocate one more for the sentinel. */
    + dev->hogs = kcalloc(num_hogs + 1, sizeof(*dev->hogs), GFP_KERNEL);
    + if (!dev->hogs)
    + return -ENOMEM;
    +
    + list_for_each_entry(bank, &dev->bank_list, siblings) {
    + list_for_each_entry(line, &bank->line_list, siblings) {
    + if (!line->hog)
    + continue;
    +
    + hog = &dev->hogs[idx++];
    +
    + /*
    + * We need to make this string manually because at this
    + * point the device doesn't exist yet and so dev_name()
    + * is not available.
    + */
    + hog->chip_label = kasprintf(GFP_KERNEL,
    + "gpio-sim.%u-%s", dev->id,
    + fwnode_get_name(bank->swnode));
    + if (!hog->chip_label) {
    + gpio_sim_remove_hogs(dev);
    + return -ENOMEM;
    + }
    +
    + /*
    + * We need to duplicate this because the hog config
    + * item can be removed at any time (and we can't block
    + * it) and gpiolib doesn't make a deep copy of the hog
    + * data.
    + */
    + if (line->hog->name) {
    + hog->line_name = kstrdup(line->hog->name,
    + GFP_KERNEL);
    + if (!hog->line_name) {
    + gpio_sim_remove_hogs(dev);
    + return -ENOMEM;
    + }
    + }
    +
    + hog->chip_hwnum = line->offset;
    + hog->dflags = line->hog->dir;
    + }
    + }
    +
    + gpiod_add_hogs(dev->hogs);
    +
    + return 0;
    +}
    +
    +struct fwnode_handle *gpio_sim_make_bank_swnode(struct gpio_sim_bank *bank,
    + struct fwnode_handle *parent)
    +{
    + struct property_entry properties[GPIO_SIM_PROP_MAX];
    + unsigned int prop_idx = 0, line_names_size = 0;
    + struct fwnode_handle *swnode;
    + char **line_names;
    +
    + memset(properties, 0, sizeof(properties));
    +
    + properties[prop_idx++] = PROPERTY_ENTRY_U32("ngpios", bank->num_lines);
    +
    + if (bank->label)
    + properties[prop_idx++] = PROPERTY_ENTRY_STRING("gpio-sim,label",
    + bank->label);
    +
    + line_names = gpio_sim_make_line_names(bank, &line_names_size);
    + if (IS_ERR(line_names))
    + return ERR_CAST(line_names);
    +
    + if (line_names)
    + properties[prop_idx++] = PROPERTY_ENTRY_STRING_ARRAY_LEN(
    + "gpio-line-names",
    + line_names, line_names_size);
    +
    + swnode = fwnode_create_software_node(properties, parent);
    + kfree(line_names);
    + return swnode;
    +}
    +
    +static void gpio_sim_remove_swnode_recursive(struct fwnode_handle *swnode)
    +{
    + struct fwnode_handle *child;
    +
    + fwnode_for_each_child_node(swnode, child)
    + fwnode_remove_software_node(child);
    +
    + fwnode_remove_software_node(swnode);
    +}
    +
    +static bool gpio_sim_bank_labels_non_unique(struct gpio_sim_device *dev)
    +{
    + struct gpio_sim_bank *this, *pos;
    +
    + list_for_each_entry(this, &dev->bank_list, siblings) {
    + list_for_each_entry(pos, &dev->bank_list, siblings) {
    + if (this == pos || (!this->label || !pos->label))
    + continue;
    +
    + if (strcmp(this->label, pos->label) == 0)
    + return true;
    + }
    + }
    +
    + return false;
    +}
    +
    +static int gpio_sim_device_activate_unlocked(struct gpio_sim_device *dev)
    +{
    + struct platform_device_info pdevinfo;
    + struct fwnode_handle *swnode;
    + struct platform_device *pdev;
    + struct gpio_sim_bank *bank;
    + int ret;
    +
    + if (list_empty(&dev->bank_list))
    + return -ENODATA;
    +
    + /*
    + * Non-unique GPIO device labels are a corner-case we don't support
    + * as it would interfere with machine hogging mechanism and has little
    + * use in real life.
    + */
    + if (gpio_sim_bank_labels_non_unique(dev))
    + return -EINVAL;
    +
    + memset(&pdevinfo, 0, sizeof(pdevinfo));
    +
    + swnode = fwnode_create_software_node(NULL, NULL);
    + if (IS_ERR(swnode))
    + return PTR_ERR(swnode);
    +
    + list_for_each_entry(bank, &dev->bank_list, siblings) {
    + bank->swnode = gpio_sim_make_bank_swnode(bank, swnode);
    + if (ret) {
    + gpio_sim_remove_swnode_recursive(swnode);
    + return ret;
    + }
    + }
    +
    + ret = gpio_sim_add_hogs(dev);
    + if (ret) {
    + gpio_sim_remove_swnode_recursive(swnode);
    + return ret;
    + }
    +
    + pdevinfo.name = "gpio-sim";
    + pdevinfo.fwnode = swnode;
    + pdevinfo.id = dev->id;
    +
    + reinit_completion(&dev->probe_completion);
    + dev->driver_bound = false;
    + bus_register_notifier(&platform_bus_type, &dev->bus_notifier);
    +
    + pdev = platform_device_register_full(&pdevinfo);
    + if (IS_ERR(pdev)) {
    + bus_unregister_notifier(&platform_bus_type, &dev->bus_notifier);
    + gpio_sim_remove_hogs(dev);
    + gpio_sim_remove_swnode_recursive(swnode);
    + return PTR_ERR(pdev);
    + }
    +
    + wait_for_completion(&dev->probe_completion);
    + bus_unregister_notifier(&platform_bus_type, &dev->bus_notifier);
    +
    + if (!dev->driver_bound) {
    + /* Probe failed, check kernel log. */
    + platform_device_unregister(pdev);
    + gpio_sim_remove_hogs(dev);
    + gpio_sim_remove_swnode_recursive(swnode);
    + return -ENXIO;
    + }
    +
    + dev->pdev = pdev;
    +
    + return 0;
    +}
    +
    +static void gpio_sim_device_deactivate_unlocked(struct gpio_sim_device *dev)
    +{
    + struct fwnode_handle *swnode;
    +
    + swnode = dev_fwnode(&dev->pdev->dev);
    + platform_device_unregister(dev->pdev);
    + gpio_sim_remove_swnode_recursive(swnode);
    + dev->pdev = NULL;
    + gpio_sim_remove_hogs(dev);
    +}
    +
    +static ssize_t
    +gpio_sim_device_config_live_store(struct config_item *item,
    + const char *page, size_t count)
    +{
    + struct gpio_sim_device *dev = to_gpio_sim_device(item);
    + int live, ret;
    +
    + ret = kstrtouint(page, 10, &live);
    + if (ret)
    + return ret;
    +
    + mutex_lock(&dev->lock);
    +
    + if ((live == 0 && !gpio_sim_device_is_live_unlocked(dev)) ||
    + (live == 1 && gpio_sim_device_is_live_unlocked(dev)))
    + ret = -EPERM;
    + else if (live == 1)
    + ret = gpio_sim_device_activate_unlocked(dev);
    + else if (live == 0)
    + gpio_sim_device_deactivate_unlocked(dev);
    + else
    + ret = -EINVAL;
    +
    + mutex_unlock(&dev->lock);
    +
    + return ret ?: count;
    +}
    +
    +CONFIGFS_ATTR(gpio_sim_device_config_, live);
    +
    +static struct configfs_attribute *gpio_sim_device_config_attrs[] = {
    + &gpio_sim_device_config_attr_dev_name,
    + &gpio_sim_device_config_attr_live,
    + NULL
    +};
    +
    +struct gpio_sim_chip_name_ctx {
    + struct gpio_sim_device *dev;
    + char *page;
    +};
    +
    +static int gpio_sim_emit_chip_name(struct device *dev, void *data)
    +{
    + struct gpio_sim_chip_name_ctx *ctx = data;
    + struct fwnode_handle *swnode;
    + struct gpio_sim_bank *bank;
    +
    + /* This would be the sysfs device exported in /sys/class/gpio. */
    + if (dev->class)
    + return 0;
    +
    + swnode = dev_fwnode(dev);
    +
    + list_for_each_entry(bank, &ctx->dev->bank_list, siblings) {
    + if (bank->swnode == swnode)
    + return sprintf(ctx->page, "%s\n", dev_name(dev));
    + }
    +
    + return -ENODATA;
    +}
    +
    +static ssize_t gpio_sim_bank_config_chip_name_show(struct config_item *item,
    + char *page)
    +{
    + struct gpio_sim_bank *bank = to_gpio_sim_bank(item);
    + struct gpio_sim_device *dev = gpio_sim_bank_get_device(bank);
    + struct gpio_sim_chip_name_ctx ctx = { dev, page };
    + int ret;
    +
    + mutex_lock(&dev->lock);
    + if (gpio_sim_device_is_live_unlocked(dev))
    + ret = device_for_each_child(&dev->pdev->dev, &ctx,
    + gpio_sim_emit_chip_name);
    + else
    + ret = sprintf(page, "none\n");
    + mutex_unlock(&dev->lock);
    +
    + return ret;
    +}
    +
    +CONFIGFS_ATTR_RO(gpio_sim_bank_config_, chip_name);
    +
    +static ssize_t
    +gpio_sim_bank_config_label_show(struct config_item *item, char *page)
    +{
    + struct gpio_sim_bank *bank = to_gpio_sim_bank(item);
    + struct gpio_sim_device *dev = gpio_sim_bank_get_device(bank);
    + int ret;
    +
    + mutex_lock(&dev->lock);
    + ret = sprintf(page, "%s\n", bank->label ?: "");
    + mutex_unlock(&dev->lock);
    +
    + return ret;
    +}
    +
    +static ssize_t gpio_sim_bank_config_label_store(struct config_item *item,
    + const char *page, size_t count)
    +{
    + struct gpio_sim_bank *bank = to_gpio_sim_bank(item);
    + struct gpio_sim_device *dev = gpio_sim_bank_get_device(bank);
    + char *trimmed;
    +
    + mutex_lock(&dev->lock);
    +
    + if (gpio_sim_device_is_live_unlocked(dev)) {
    + mutex_unlock(&dev->lock);
    + return -EBUSY;
    + }
    +
    + trimmed = gpio_sim_strdup_trimmed(page, count);
    + if (!trimmed) {
    + mutex_unlock(&dev->lock);
    + return -ENOMEM;
    + }
    +
    + kfree(bank->label);
    + bank->label = trimmed;
    +
    + mutex_unlock(&dev->lock);
    + return count;
    +}
    +
    +CONFIGFS_ATTR(gpio_sim_bank_config_, label);
    +
    +static ssize_t
    +gpio_sim_bank_config_num_lines_show(struct config_item *item, char *page)
    +{
    + struct gpio_sim_bank *bank = to_gpio_sim_bank(item);
    + struct gpio_sim_device *dev = gpio_sim_bank_get_device(bank);
    + int ret;
    +
    + mutex_lock(&dev->lock);
    + ret = sprintf(page, "%u\n", bank->num_lines);
    + mutex_unlock(&dev->lock);
    +
    + return ret;
    +}
    +
    +static ssize_t
    +gpio_sim_bank_config_num_lines_store(struct config_item *item,
    + const char *page, size_t count)
    +{
    + struct gpio_sim_bank *bank = to_gpio_sim_bank(item);
    + struct gpio_sim_device *dev = gpio_sim_bank_get_device(bank);
    + unsigned int num_lines;
    + int ret;
    +
    + ret = kstrtouint(page, 10, &num_lines);
    + if (ret)
    + return ret;
    +
    + if (num_lines == 0)
    + return -EINVAL;
    +
    + mutex_lock(&dev->lock);
    +
    + if (gpio_sim_device_is_live_unlocked(dev)) {
    + mutex_unlock(&dev->lock);
    + return -EBUSY;
    + }
    +
    + bank->num_lines = num_lines;
    +
    + mutex_unlock(&dev->lock);
    + return count;
    +}
    +
    +CONFIGFS_ATTR(gpio_sim_bank_config_, num_lines);
    +
    +static struct configfs_attribute *gpio_sim_bank_config_attrs[] = {
    + &gpio_sim_bank_config_attr_chip_name,
    + &gpio_sim_bank_config_attr_label,
    + &gpio_sim_bank_config_attr_num_lines,
    + NULL
    +};
    +
    +static ssize_t
    +gpio_sim_line_config_name_show(struct config_item *item, char *page)
    +{
    + struct gpio_sim_line *line = to_gpio_sim_line(item);
    + struct gpio_sim_device *dev = gpio_sim_line_get_device(line);
    + int ret;
    +
    + mutex_lock(&dev->lock);
    + ret = sprintf(page, "%s\n", line->name ?: "");
    + mutex_unlock(&dev->lock);
    +
    + return ret;
    +}
    +
    +static ssize_t gpio_sim_line_config_name_store(struct config_item *item,
    + const char *page, size_t count)
    +{
    + struct gpio_sim_line *line = to_gpio_sim_line(item);
    + struct gpio_sim_device *dev = gpio_sim_line_get_device(line);
    + char *trimmed;
    +
    + mutex_lock(&dev->lock);
    +
    + if (gpio_sim_device_is_live_unlocked(dev)) {
    + mutex_unlock(&dev->lock);
    + return -EBUSY;
    + }
    +
    + trimmed = gpio_sim_strdup_trimmed(page, count);
    + if (!trimmed) {
    + mutex_unlock(&dev->lock);
    + return -ENOMEM;
    + }
    +
    + kfree(line->name);
    + line->name = trimmed;
    +
    + mutex_unlock(&dev->lock);
    +
    + return count;
    +}
    +
    +CONFIGFS_ATTR(gpio_sim_line_config_, name);
    +
    +static struct configfs_attribute *gpio_sim_line_config_attrs[] = {
    + &gpio_sim_line_config_attr_name,
    + NULL,
    +};
    +
    +static ssize_t gpio_sim_hog_config_name_show(struct config_item *item,
    + char *page)
    +{
    + struct gpio_sim_hog *hog = to_gpio_sim_hog(item);
    + struct gpio_sim_device *dev = gpio_sim_hog_get_device(hog);
    + int ret;
    +
    + mutex_lock(&dev->lock);
    + ret = sprintf(page, "%s\n", hog->name ?: "");
    + mutex_unlock(&dev->lock);
    +
    + return ret;
    +}
    +
    +static ssize_t gpio_sim_hog_config_name_store(struct config_item *item,
    + const char *page, size_t count)
    +{
    + struct gpio_sim_hog *hog = to_gpio_sim_hog(item);
    + struct gpio_sim_device *dev = gpio_sim_hog_get_device(hog);
    + char *trimmed;
    +
    + mutex_lock(&dev->lock);
    +
    + if (gpio_sim_device_is_live_unlocked(dev)) {
    + mutex_unlock(&dev->lock);
    + return -EBUSY;
    + }
    +
    + trimmed = gpio_sim_strdup_trimmed(page, count);
    + if (!trimmed) {
    + mutex_unlock(&dev->lock);
    + return -ENOMEM;
    + }
    +
    + kfree(hog->name);
    + hog->name = trimmed;
    +
    + mutex_unlock(&dev->lock);
    +
    + return count;
    +}
    +
    +CONFIGFS_ATTR(gpio_sim_hog_config_, name);
    +
    +static ssize_t gpio_sim_hog_config_direction_show(struct config_item *item,
    + char *page)
    +{
    + struct gpio_sim_hog *hog = to_gpio_sim_hog(item);
    + struct gpio_sim_device *dev = gpio_sim_hog_get_device(hog);
    + char *repr;
    + int dir;
    +
    + mutex_lock(&dev->lock);
    + dir = hog->dir;
    + mutex_unlock(&dev->lock);
    +
    + switch (dir) {
    + case GPIOD_IN:
    + repr = "input";
    + break;
    + case GPIOD_OUT_HIGH:
    + repr = "output-high";
    + break;
    + case GPIOD_OUT_LOW:
    + repr = "output-low";
    + break;
    + default:
    + /* This would be a programmer bug. */
    + WARN(1, "Unexpected hog direction value: %d", dir);
    + return -EINVAL;
    + }
    +
    + return sprintf(page, "%s\n", repr);
    +}
    +
    +static ssize_t
    +gpio_sim_hog_config_direction_store(struct config_item *item,
    + const char *page, size_t count)
    +{
    + struct gpio_sim_hog *hog = to_gpio_sim_hog(item);
    + struct gpio_sim_device *dev = gpio_sim_hog_get_device(hog);
    + char *trimmed;
    + int dir;
    +
    + mutex_lock(&dev->lock);
    +
    + if (gpio_sim_device_is_live_unlocked(dev)) {
    + mutex_unlock(&dev->lock);
    + return -EBUSY;
    + }
    +
    + trimmed = gpio_sim_strdup_trimmed(page, count);
    + if (!trimmed) {
    + mutex_unlock(&dev->lock);
    + return -ENOMEM;
    + }
    +
    + if (strcmp(trimmed, "input") == 0)
    + dir = GPIOD_IN;
    + else if (strcmp(trimmed, "output-high") == 0)
    + dir = GPIOD_OUT_HIGH;
    + else if (strcmp(trimmed, "output-low") == 0)
    + dir = GPIOD_OUT_LOW;
    + else
    + dir = -EINVAL;
    +
    + kfree(trimmed);
    +
    + if (dir < 0) {
    + mutex_unlock(&dev->lock);
    + return dir;
    + }
    +
    + hog->dir = dir;
    +
    + mutex_unlock(&dev->lock);
    +
    + return count;
    +}
    +
    +CONFIGFS_ATTR(gpio_sim_hog_config_, direction);
    +
    +static struct configfs_attribute *gpio_sim_hog_config_attrs[] = {
    + &gpio_sim_hog_config_attr_name,
    + &gpio_sim_hog_config_attr_direction,
    + NULL,
    +};
    +
    +static void gpio_sim_hog_config_item_release(struct config_item *item)
    +{
    + struct gpio_sim_hog *hog = to_gpio_sim_hog(item);
    + struct gpio_sim_line *line = hog->parent;
    + struct gpio_sim_device *dev = gpio_sim_hog_get_device(hog);
    +
    + mutex_lock(&dev->lock);
    + line->hog = NULL;
    + mutex_unlock(&dev->lock);
    +
    + kfree(hog->name);
    + kfree(hog);
    +}
    +
    +struct configfs_item_operations gpio_sim_hog_config_item_ops = {
    + .release = gpio_sim_hog_config_item_release,
    +};
    +
    +static const struct config_item_type gpio_sim_hog_config_type = {
    + .ct_item_ops = &gpio_sim_hog_config_item_ops,
    + .ct_attrs = gpio_sim_hog_config_attrs,
    + .ct_owner = THIS_MODULE,
    +};
    +
    +static struct config_item *
    +gpio_sim_line_config_make_hog_item(struct config_group *group, const char *name)
    +{
    + struct gpio_sim_line *line = to_gpio_sim_line(&group->cg_item);
    + struct gpio_sim_device *dev = gpio_sim_line_get_device(line);
    + struct gpio_sim_hog *hog;
    +
    + if (strcmp(name, "hog") != 0)
    + return ERR_PTR(-EINVAL);
    +
    + mutex_lock(&dev->lock);
    +
    + hog = kzalloc(sizeof(*hog), GFP_KERNEL);
    + if (!hog) {
    + mutex_unlock(&dev->lock);
    + return ERR_PTR(-ENOMEM);
    + }
    +
    + config_item_init_type_name(&hog->item, name,
    + &gpio_sim_hog_config_type);
    +
    + hog->dir = GPIOD_IN;
    + hog->name = NULL;
    + hog->parent = line;
    + line->hog = hog;
    +
    + mutex_unlock(&dev->lock);
    +
    + return &hog->item;
    +}
    +
    +static void gpio_sim_line_config_group_release(struct config_item *item)
    +{
    + struct gpio_sim_line *line = to_gpio_sim_line(item);
    + struct gpio_sim_device *dev = gpio_sim_line_get_device(line);
    +
    + mutex_lock(&dev->lock);
    + list_del(&line->siblings);
    + mutex_unlock(&dev->lock);
    +
    + kfree(line->name);
    + kfree(line);
    +}
    +
    +static struct configfs_item_operations gpio_sim_line_config_item_ops = {
    + .release = gpio_sim_line_config_group_release,
    +};
    +
    +static struct configfs_group_operations gpio_sim_line_config_group_ops = {
    + .make_item = gpio_sim_line_config_make_hog_item,
    +};
    +
    +static const struct config_item_type gpio_sim_line_config_type = {
    + .ct_item_ops = &gpio_sim_line_config_item_ops,
    + .ct_group_ops = &gpio_sim_line_config_group_ops,
    + .ct_attrs = gpio_sim_line_config_attrs,
    + .ct_owner = THIS_MODULE,
    +};
    +
    +static struct config_group *
    +gpio_sim_bank_config_make_line_group(struct config_group *group,
    + const char *name)
    +{
    + struct gpio_sim_bank *bank = to_gpio_sim_bank(&group->cg_item);
    + struct gpio_sim_device *dev = gpio_sim_bank_get_device(bank);
    + struct gpio_sim_line *line;
    + unsigned int offset;
    + int ret, nchar;
    +
    + ret = sscanf(name, "line%u%n", &offset, &nchar);
    + if (ret != 1 || nchar != strlen(name))
    + return ERR_PTR(-EINVAL);
    +
    + mutex_lock(&dev->lock);
    +
    + if (gpio_sim_device_is_live_unlocked(dev)) {
    + mutex_unlock(&dev->lock);
    + return ERR_PTR(-EBUSY);
    + }
    +
    + line = kzalloc(sizeof(*line), GFP_KERNEL);
    + if (!line) {
    + mutex_unlock(&dev->lock);
    + return ERR_PTR(-ENOMEM);
    + }
    +
    + config_group_init_type_name(&line->group, name,
    + &gpio_sim_line_config_type);
    +
    + line->parent = bank;
    + line->offset = offset;
    + list_add_tail(&line->siblings, &bank->line_list);
    +
    + mutex_unlock(&dev->lock);
    +
    + return &line->group;
    +}
    +
    +static void gpio_sim_bank_config_group_release(struct config_item *item)
    +{
    + struct gpio_sim_bank *bank = to_gpio_sim_bank(item);
    + struct gpio_sim_device *dev = gpio_sim_bank_get_device(bank);
    +
    + mutex_lock(&dev->lock);
    + list_del(&bank->siblings);
    + mutex_unlock(&dev->lock);
    +
    + kfree(bank->label);
    + kfree(bank);
    +}
    +
    +static struct configfs_item_operations gpio_sim_bank_config_item_ops = {
    + .release = gpio_sim_bank_config_group_release,
    +};
    +
    +static struct configfs_group_operations gpio_sim_bank_config_group_ops = {
    + .make_group = gpio_sim_bank_config_make_line_group,
    +};
    +
    +static const struct config_item_type gpio_sim_bank_config_group_type = {
    + .ct_item_ops = &gpio_sim_bank_config_item_ops,
    + .ct_group_ops = &gpio_sim_bank_config_group_ops,
    + .ct_attrs = gpio_sim_bank_config_attrs,
    + .ct_owner = THIS_MODULE,
    +};
    +
    +static struct config_group *
    +gpio_sim_device_config_make_bank_group(struct config_group *group,
    + const char *name)
    +{
    + struct gpio_sim_device *dev = to_gpio_sim_device(&group->cg_item);
    + struct gpio_sim_bank *bank;
    +
    + mutex_lock(&dev->lock);
    +
    + if (gpio_sim_device_is_live_unlocked(dev)) {
    + mutex_unlock(&dev->lock);
    + return ERR_PTR(-EBUSY);
    + }
    +
    + bank = kzalloc(sizeof(*bank), GFP_KERNEL);
    + if (!bank) {
    + mutex_unlock(&dev->lock);
    + return ERR_PTR(-ENOMEM);
    + }
    +
    + config_group_init_type_name(&bank->group, name,
    + &gpio_sim_bank_config_group_type);
    + bank->num_lines = 1;
    + bank->parent = dev;
    + INIT_LIST_HEAD(&bank->line_list);
    + list_add_tail(&bank->siblings, &dev->bank_list);
    +
    + mutex_unlock(&dev->lock);
    +
    + return &bank->group;
    +}
    +
    +static void gpio_sim_device_config_group_release(struct config_item *item)
    +{
    + struct gpio_sim_device *dev = to_gpio_sim_device(item);
    +
    + mutex_lock(&dev->lock);
    + if (gpio_sim_device_is_live_unlocked(dev))
    + gpio_sim_device_deactivate_unlocked(dev);
    + mutex_unlock(&dev->lock);
    +
    + mutex_destroy(&dev->lock);
    + ida_free(&gpio_sim_ida, dev->id);
    + kfree(dev);
    +}
    +
    +static struct configfs_item_operations gpio_sim_device_config_item_ops = {
    + .release = gpio_sim_device_config_group_release,
    +};
    +
    +static struct configfs_group_operations gpio_sim_device_config_group_ops = {
    + .make_group = gpio_sim_device_config_make_bank_group,
    +};
    +
    +static const struct config_item_type gpio_sim_device_config_group_type = {
    + .ct_item_ops = &gpio_sim_device_config_item_ops,
    + .ct_group_ops = &gpio_sim_device_config_group_ops,
    + .ct_attrs = gpio_sim_device_config_attrs,
    + .ct_owner = THIS_MODULE,
    +};
    +
    +static struct config_group *
    +gpio_sim_config_make_device_group(struct config_group *group, const char *name)
    +{
    + struct gpio_sim_device *dev;
    + int id;
    +
    + dev = kzalloc(sizeof(*dev), GFP_KERNEL);
    + if (!dev)
    + return ERR_PTR(-ENOMEM);
    +
    + id = ida_alloc(&gpio_sim_ida, GFP_KERNEL);
    + if (id < 0) {
    + kfree(dev);
    + return ERR_PTR(id);
    + }
    +
    + config_group_init_type_name(&dev->group, name,
    + &gpio_sim_device_config_group_type);
    + dev->id = id;
    + mutex_init(&dev->lock);
    + INIT_LIST_HEAD(&dev->bank_list);
    +
    + dev->bus_notifier.notifier_call = gpio_sim_bus_notifier_call;
    + init_completion(&dev->probe_completion);
    +
    + return &dev->group;
    +}
    +
    +static struct configfs_group_operations gpio_sim_config_group_ops = {
    + .make_group = gpio_sim_config_make_device_group,
    +};
    +
    +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 <brgl@bgdev.pl");
    +MODULE_DESCRIPTION("GPIO Simulator Module");
    +MODULE_LICENSE("GPL");
    --
    2.25.1
    \
     
     \ /
      Last update: 2021-11-30 16:43    [W:3.323 / U:0.128 seconds]
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