On Thu, Mar 04, 2021 at 11:24:49AM +0100, Bartosz Golaszewski wrote:

From: Bartosz Golaszewski <redacted>

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.

Shall we put a reference to this in the gpio-mockup documentation and mark the
latter deprecated?

+		dev_attr->attr.name = devm_kasprintf(dev, GFP_KERNEL,
+						     "gpio%u", i);

Reads better as one line.

+		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_zalloc(dev, num_lines, GFP_KERNEL);

What's the point to have "z" variant here...

+	if (!chip->directions)
+		return -ENOMEM;
+
+	/* Default to input mode. */
+	bitmap_fill(chip->directions, num_lines);

...followed by filling all 1:s here?

+	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",
+	},
+	.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;
+
+	/*
+	 * 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 && device_is_bound(&pdev->dev))
+		ret = sprintf(page, "%s\n", dev_name(&pdev->dev));
+	else
+		ret = -ENODEV;
+	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 platform_device *pdev;
+	struct gpio_sim_chip *chip;
+	int ret;
+
+	mutex_lock(&config->lock);
+	pdev = config->pdev;
+	if (pdev && device_is_bound(&pdev->dev)) {
+		chip = dev_get_drvdata(&pdev->dev);
+		ret = sprintf(page, "%s\n", dev_name(&chip->gc.gpiodev->dev));
+	} else {
+		ret = -ENODEV;
+	}
+	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] ?: "");

Indentation here looks not the best...

+		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;
+	}
+
+	/*
+	 * FIXME If anyone knows a better way to parse that - please let me
+	 * know.
+	 */

If comma can be replaced with ' ' (space) then why not to use next_arg() from
cmdline.c? I.o.w. do you have strong opinion why should we use comma here?

+	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 = kzalloc(name_len + 1, GFP_KERNEL);
+				if (!name) {
+					err = -ENOMEM;
+					goto err_out;
+				}
+
+				memcpy(name, start, name_len);

kmemdup()/kstrndup() or so?

+				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);
+	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;
+
+	config = kzalloc(sizeof(*config), GFP_KERNEL);
+	if (!config)
+		return ERR_PTR(-ENOMEM);
+
+	config_item_init_type_name(&config->item, name,
+				   &gpio_sim_chip_config_type);
+	config->num_lines = 1;
+	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 property_entry properties[GPIO_SIM_MAX_PROP];
+	struct platform_device_info pdevinfo;
+	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.id = ida_alloc(&gpio_sim_ida, GFP_KERNEL);
+	if (pdevinfo.id < 0) {
+		mutex_unlock(&config->lock);
+		return pdevinfo.id;
+	}
+
+	pdevinfo.name = "gpio-sim";
+	pdevinfo.properties = properties;
+
+	pdev = platform_device_register_full(&pdevinfo);
+	if (IS_ERR(pdev)) {
+		ida_free(&gpio_sim_ida, pdevinfo.id);
+		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);
+	int id;
+
+	mutex_lock(&config->lock);
+	id = config->pdev->id;
+	platform_device_unregister(config->pdev);
+	config->pdev = NULL;

+	ida_free(&gpio_sim_ida, id);

Isn't it atomic per se? I mean that IDA won't give the same ID until you free
it. I.o.w. why is it under the mutex?

+	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 [off-list ref]");
+MODULE_DESCRIPTION("GPIO Simulator Module");
+MODULE_LICENSE("GPL");
-- 
2.29.1

-- 
With Best Regards,
Andy Shevchenko