[PATCH 22/23] gpio: mockup: provide a way to create new dummy chips

[Bartosz Golaszewski <brgl@xxxxxxxx>]

From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>

Add a new debugfs attribute 'new_device' that allows to dynamically
create new dummy chips according to specification.

New chips are created by writing a number of supported parameters to the
new attribute of which 'label' and 'num_lines' are mandatory. The new
attribute is designed to be easily exstensible with new parameters. For
now we simply provide the same functionality that the module params
expose but with the intention of introducing new options (such as custom
line name formats).

Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
---
 drivers/gpio/gpio-mockup.c | 231 +++++++++++++++++++++++++++++++++++--
 1 file changed, 220 insertions(+), 11 deletions(-)

diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
index 9d2de78a45c2..6577d18671df 100644
--- a/drivers/gpio/gpio-mockup.c
+++ b/drivers/gpio/gpio-mockup.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2014  Kamlakant Patel <kamlakant.patel@xxxxxxxxxxxx>
  * Copyright (C) 2015-2016  Bamvor Jian Zhang <bamv2005@xxxxxxxxx>
  * Copyright (C) 2017 Bartosz Golaszewski <brgl@xxxxxxxx>
+ * Copyright (C) 2020 Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
  */
 
 #include <linux/debugfs.h>
@@ -14,6 +15,7 @@
 #include <linux/irq.h>
 #include <linux/irq_sim.h>
 #include <linux/irqdomain.h>
+#include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -546,8 +548,8 @@ static void gpio_mockup_unregister_devices(void)
 	mutex_unlock(&gpio_mockup_devices_lock);
 }
 
-static __init char **gpio_mockup_make_line_names(const char *label,
-						 unsigned int num_lines)
+static char **gpio_mockup_make_line_names(const char *label,
+					  unsigned int num_lines)
 {
 	unsigned int i;
 	char **names;
@@ -567,7 +569,7 @@ static __init char **gpio_mockup_make_line_names(const char *label,
 	return names;
 }
 
-static int __init gpio_mockup_register_device(struct property_entry *properties)
+static int gpio_mockup_register_device(struct property_entry *properties)
 {
 	struct gpio_mockup_device *mockup_dev;
 	struct platform_device_info pdevinfo;
@@ -641,8 +643,7 @@ static int __init gpio_mockup_register_chips_from_params(void)
 {
 	int num_chips, i, ret;
 
-	if ((gpio_mockup_num_ranges < 2) ||
-	    (gpio_mockup_num_ranges % 2) ||
+	if ((gpio_mockup_num_ranges % 2) ||
 	    (gpio_mockup_num_ranges > GPIO_MOCKUP_MAX_RANGES))
 		return -EINVAL;
 
@@ -669,6 +670,205 @@ static int __init gpio_mockup_register_chips_from_params(void)
 	return 0;
 }
 
+/*
+ * We store all data associated with device properties in this structure. It's
+ * only needed until we register the platform device at which point the driver
+ * core makes a deep copy of all property data (even the string arrays).
+ *
+ * The reason to keep them bunched up is simple: we can have a single function
+ * to free all resources which simplifies error handling.
+ */
+struct gpio_mockup_prop_data {
+	char chip_label[GPIO_MOCKUP_LABEL_SIZE];
+	u16 ngpio;
+	bool named_lines;
+	char **line_names;
+};
+
+/* We don't free the structure itself - it's expected to live on the stack. */
+static void
+gpio_mockup_free_property_data(struct gpio_mockup_prop_data *prop_data)
+{
+	kfree_strarray(prop_data->line_names, prop_data->ngpio);
+}
+
+/*
+ * Each supported option is parsed by a separate callback - this way the
+ * 'new_device' attribute is easily exstensible.
+ */
+struct gpio_mockup_new_device_opt {
+	char *name;
+	int (*func)(const char *val, struct gpio_mockup_prop_data *prop_data,
+		    struct property_entry *properties, int *prop_idx);
+	bool has_val;
+};
+
+static int
+gpio_mockup_parse_label(const char *val,
+		struct gpio_mockup_prop_data *prop_data,
+		struct property_entry *properties, int *prop_idx)
+{
+	snprintf(prop_data->chip_label, sizeof(prop_data->chip_label), val);
+	properties[(*prop_idx)++] =
+		PROPERTY_ENTRY_STRING("chip-label", prop_data->chip_label);
+
+	return 0;
+}
+
+static int gpio_mockup_parse_num_lines(const char *val,
+			struct gpio_mockup_prop_data *prop_data,
+			struct property_entry *properties, int *prop_idx)
+{
+	int ret;
+
+	ret = kstrtou16(val, 10, &prop_data->ngpio);
+	if (ret) {
+		pr_err("invalid new_lines format: %s\n", val);
+		return ret;
+	}
+
+	properties[(*prop_idx)++] = PROPERTY_ENTRY_U16("nr-gpios",
+						     prop_data->ngpio);
+
+	return 0;
+}
+
+static int gpio_mockup_parse_named_lines(const char *val,
+			struct gpio_mockup_prop_data *prop_data,
+			struct property_entry *properties, int *prop_idx)
+{
+	prop_data->named_lines = true;
+
+	return 0;
+}
+
+static struct gpio_mockup_new_device_opt gpio_mockup_new_device_opts[] = {
+	{
+		.name = "label",
+		.func = gpio_mockup_parse_label,
+		.has_val = true,
+	},
+	{
+		.name = "num_lines",
+		.func = gpio_mockup_parse_num_lines,
+		.has_val = true,
+	},
+	{
+		.name = "named_lines",
+		.func = gpio_mockup_parse_named_lines,
+		.has_val = false,
+	},
+};
+
+static int
+gpio_mockup_parse_one_opt(const char *key, const char *val,
+			  struct gpio_mockup_prop_data *prop_data,
+			  struct property_entry *properties, int *prop_idx)
+{
+	struct gpio_mockup_new_device_opt *opt;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(gpio_mockup_new_device_opts); i++) {
+		opt = &gpio_mockup_new_device_opts[i];
+
+		if (strcmp(key, opt->name) == 0) {
+			if (opt->has_val && !val) {
+				pr_err("%s option requires an argument\n",
+				       opt->name);
+				return -EINVAL;
+			}
+
+			if (!opt->has_val && val) {
+				pr_err("%s option doesn't take any arguments\n",
+				       opt->name);
+				return -EINVAL;
+			}
+
+			return opt->func(val, prop_data, properties, prop_idx);
+		}
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int
+gpio_mockup_new_device_from_opts(char *opts,
+				 struct gpio_mockup_prop_data *prop_data)
+{
+	struct property_entry properties[GPIO_MOCKUP_MAX_PROP];
+	int prop_idx = 0, ret;
+	char *key, *val;
+
+	memset(properties, 0, sizeof(properties));
+
+	while (*opts) {
+		if (prop_idx >= GPIO_MOCKUP_MAX_PROP)
+			return -EINVAL;
+
+		opts = next_arg(opts, &key, &val);
+
+		ret = gpio_mockup_parse_one_opt(key, val, prop_data,
+						properties, &prop_idx);
+		if (ret)
+			return ret;
+	}
+
+	/* This is the only mandatory property. */
+	if (!prop_data->ngpio) {
+		pr_err("number of lines must be specified\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Line names must be created at the end - once we know how
+	 * many GPIOs there are.
+	 */
+	if (prop_data->named_lines) {
+		prop_data->line_names = gpio_mockup_make_line_names(
+							prop_data->chip_label,
+							prop_data->ngpio);
+		if (!prop_data->line_names)
+			return -ENOMEM;
+
+		properties[prop_idx++] =
+			PROPERTY_ENTRY_STRING_ARRAY_LEN("gpio-line-names",
+							prop_data->line_names,
+							prop_data->ngpio);
+	}
+
+	return gpio_mockup_register_device(properties);
+}
+
+static ssize_t gpio_mockup_debugfs_new_device_write(struct file *file,
+						    const char __user *usr_buf,
+						    size_t size, loff_t *ppos)
+{
+	struct gpio_mockup_prop_data prop_data;
+	char opts[128];
+	int ret;
+
+	if (*ppos != 0 || size > sizeof(opts))
+		return -EINVAL;
+
+	ret = getline_from_user(opts, sizeof(opts), usr_buf, size);
+	if (ret < 0)
+		return ret;
+
+	memset(&prop_data, 0, sizeof(prop_data));
+
+	ret = gpio_mockup_new_device_from_opts(opts, &prop_data);
+	gpio_mockup_free_property_data(&prop_data);
+	return ret < 0 ? ret : size;
+}
+
+static const struct file_operations gpio_mockup_debugfs_new_device_ops = {
+	.owner = THIS_MODULE,
+	.open = gpio_mockup_debugfs_open,
+	.write = gpio_mockup_debugfs_new_device_write,
+	.llseek = no_llseek,
+	.release = single_release,
+};
+
 static ssize_t gpio_mockup_debugfs_delete_device_write(struct file *file,
 						const char __user *usr_buf,
 						size_t size, loff_t *ppos)
@@ -726,6 +926,13 @@ static int __init gpio_mockup_debugfs_init(void)
 	if (IS_ERR(gpio_mockup_dbg_dir))
 		return PTR_ERR(gpio_mockup_dbg_dir);
 
+	entry = debugfs_create_file("new_device", 0200, gpio_mockup_dbg_dir,
+				NULL, &gpio_mockup_debugfs_new_device_ops);
+	if (IS_ERR(entry)) {
+		debugfs_remove_recursive(gpio_mockup_dbg_dir);
+		return PTR_ERR(entry);
+	}
+
 	entry = debugfs_create_file("delete_device", 0200, gpio_mockup_dbg_dir,
 				NULL, &gpio_mockup_debugfs_delete_device_ops);
 	if (IS_ERR(entry)) {
@@ -751,12 +958,14 @@ static int __init gpio_mockup_init(void)
 		return ret;
 	}
 
-	ret = gpio_mockup_register_chips_from_params();
-	if (ret) {
-		pr_err("error registering device");
-		debugfs_remove_recursive(gpio_mockup_dbg_dir);
-		platform_driver_unregister(&gpio_mockup_driver);
-		return ret;
+	if (gpio_mockup_ranges > 0) {
+		ret = gpio_mockup_register_chips_from_params();
+		if (ret) {
+			pr_err("error registering device");
+			debugfs_remove_recursive(gpio_mockup_dbg_dir);
+			platform_driver_unregister(&gpio_mockup_driver);
+			return ret;
+		}
 	}
 
 	return 0;
-- 
2.26.1