[PATCH v4 2/6] platform/x86: firmware_attributes_class: Add high level API for the attributes interface

[Kurt Borja]

Add high level API to aid in the creation of attribute groups attached
to the `attrs_kobj` (per ABI specification).

This new API lets users configure each group, either statically or
dynamically through a (per type) data struct and then create this group
through the generic fwat_create_group() macro.

Signed-off-by: Kurt Borja <kuurtb@xxxxxxxxx>
---
 drivers/platform/x86/firmware_attributes_class.c | 532 +++++++++++++++++++++++
 drivers/platform/x86/firmware_attributes_class.h | 335 ++++++++++++++
 2 files changed, 867 insertions(+)

diff --git a/drivers/platform/x86/firmware_attributes_class.c b/drivers/platform/x86/firmware_attributes_class.c
index 29c303c20d47a7dccf59cf54fa1a7e91e582f894..86d2a8bf4bb9debc81e38c928c5a3eb5a440cc18 100644
--- a/drivers/platform/x86/firmware_attributes_class.c
+++ b/drivers/platform/x86/firmware_attributes_class.c
@@ -10,13 +10,67 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/types.h>
+#include <linux/string_choices.h>
 #include "firmware_attributes_class.h"
 
+#define FWAT_TYPE_NONE				-1
+
+#define to_fwat_bool_data(_c) \
+	container_of_const(_c, struct fwat_bool_data, group)
+#define to_fwat_enum_data(_c) \
+	container_of_const(_c, struct fwat_enum_data, group)
+#define to_fwat_int_data(_c) \
+	container_of_const(_c, struct fwat_int_data, group)
+#define to_fwat_str_data(_c) \
+	container_of_const(_c, struct fwat_str_data, group)
+
+struct fwat_attribute {
+	struct attribute attr;
+	ssize_t (*show)(struct kobject *kobj, struct fwat_attribute *attr,
+			char *buf);
+	ssize_t (*store)(struct kobject *kobj, struct fwat_attribute *attr,
+			 const char *buf, size_t count);
+	int type;
+};
+
+#define to_fwat_attribute(_a) \
+	container_of_const(_a, struct fwat_attribute, attr)
+
+#define __FWAT_ATTR(_name, _mode, _show, _store, _type) \
+	{								\
+		.attr = { .name = __stringify(_name), .mode = _mode },	\
+		.show = _show, .store = _store, .type = _type,		\
+	}
+
+#define FWAT_ATTR_RO(_prefix, _name, _show, _type) \
+	static struct fwat_attribute fwat_##_prefix##_##_name##_attr = \
+		__FWAT_ATTR(_name, 0444, _show, NULL, _type)
+
+#define FWAT_ATTR_RW(_prefix, _name, _show, _store, _type) \
+	static struct fwat_attribute fwat_##_prefix##_##_name##_attr = \
+		__FWAT_ATTR(_name, 0644, _show, _store, _type)
+
+struct fwat_group {
+	const struct fwat_group_data *data;
+	struct device *dev;
+	struct kobject kobj;
+};
+
+#define kobj_to_fwat_group(_k) \
+	container_of_const(_k, struct fwat_group, kobj)
+
 const struct class firmware_attributes_class = {
 	.name = "firmware-attributes",
 };
 EXPORT_SYMBOL_GPL(firmware_attributes_class);
 
+static const char * const fwat_type_labels[] = {
+	[fwat_group_boolean]			= "boolean",
+	[fwat_group_enumeration]		= "enumeration",
+	[fwat_group_integer]			= "integer",
+	[fwat_group_string]			= "string",
+};
+
 static void fwat_device_release(struct device *dev)
 {
 	struct fwat_device *fadev = to_fwat_device(dev);
@@ -24,6 +78,483 @@ static void fwat_device_release(struct device *dev)
 	kfree(fadev);
 }
 
+static ssize_t
+type_show(struct kobject *kobj, struct fwat_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", fwat_type_labels[attr->type]);
+}
+
+static ssize_t
+display_name_show(struct kobject *kobj, struct fwat_attribute *attr, char *buf)
+{
+	struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const char *disp_name = group->data->display_name;
+
+	if (!disp_name)
+		return -EOPNOTSUPP;
+
+	return sysfs_emit(buf, "%s\n", disp_name);
+}
+
+static ssize_t
+display_name_language_code_show(struct kobject *kobj, struct fwat_attribute *attr,
+				char *buf)
+{
+	struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const char *lang_code = group->data->language_code;
+
+	if (!lang_code)
+		return -EOPNOTSUPP;
+
+	return sysfs_emit(buf, "%s\n", lang_code);
+}
+
+static ssize_t
+bool_group_show(struct kobject *kobj, struct fwat_attribute *attr, char *buf)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_bool_data *data = to_fwat_bool_data(group->data);
+	bool val;
+	int ret;
+
+	/* show_override does not affect current_value */
+	if (data->group.show_override && attr->type != fwat_bool_current_value)
+		return data->group.show_override(group->dev, attr->type, buf);
+
+	switch (attr->type) {
+	case fwat_bool_current_value:
+		ret = data->read(group->dev, data->group.id, &val);
+		if (ret < 0)
+			return ret;
+		break;
+	case fwat_bool_default_value:
+		val = data->default_val;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return sysfs_emit(buf, "%s\n", str_yes_no(val));
+}
+
+static ssize_t
+bool_group_store(struct kobject *kobj, struct fwat_attribute *attr, const char *buf,
+		 size_t count)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_bool_data *data = to_fwat_bool_data(group->data);
+	bool val;
+	int ret;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	ret = data->write(group->dev, data->group.id, val);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static ssize_t
+enum_group_show(struct kobject *kobj, struct fwat_attribute *attr, char *buf)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_enum_data *data = to_fwat_enum_data(group->data);
+	int val_idx, sz = 0;
+	int ret;
+
+	/* show_override does not affect current_value */
+	if (data->group.show_override && attr->type != fwat_enum_current_value)
+		return data->group.show_override(group->dev, attr->type, buf);
+
+	switch (attr->type) {
+	case fwat_enum_current_value:
+		ret = data->read(group->dev, data->group.id, &val_idx);
+		if (ret < 0)
+			return ret;
+		break;
+	case fwat_enum_default_value:
+		val_idx = data->default_idx;
+		break;
+	case fwat_enum_possible_values:
+		sz += sysfs_emit_at(buf, sz, "%s", data->possible_vals[0]);
+		for (unsigned int i = 1; data->possible_vals[i]; i++)
+			sz += sysfs_emit_at(buf, sz, ";%s", data->possible_vals[i]);
+		sz += sysfs_emit_at(buf, sz, "\n");
+		return sz;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return sysfs_emit(buf, "%s\n", data->possible_vals[val_idx]);
+}
+
+static ssize_t
+enum_group_store(struct kobject *kobj, struct fwat_attribute *attr, const char *buf,
+		 size_t count)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_enum_data *data = to_fwat_enum_data(group->data);
+	int val_idx;
+	int ret;
+
+	val_idx = __sysfs_match_string(data->possible_vals, -1, buf);
+	if (val_idx < 0)
+		return val_idx;
+
+	ret = data->write(group->dev, data->group.id, val_idx);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static ssize_t
+int_group_show(struct kobject *kobj, struct fwat_attribute *attr, char *buf)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_int_data *data = to_fwat_int_data(group->data);
+	long val;
+	int ret;
+
+	/* show_override does not affect current_value */
+	if (data->group.show_override && attr->type != fwat_int_current_value)
+		return data->group.show_override(group->dev, attr->type, buf);
+
+	switch (attr->type) {
+	case fwat_int_current_value:
+		ret = data->read(group->dev, data->group.id, &val);
+		if (ret < 0)
+			return ret;
+		break;
+	case fwat_int_default_value:
+		val = data->default_val;
+		break;
+	case fwat_int_min_value:
+		val = data->min_val;
+		break;
+	case fwat_int_max_value:
+		val = data->max_val;
+		break;
+	case fwat_int_scalar_increment:
+		val = data->increment;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return sysfs_emit(buf, "%ld\n", val);
+}
+
+static ssize_t
+int_group_store(struct kobject *kobj, struct fwat_attribute *attr, const char *buf,
+		size_t count)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_int_data *data = to_fwat_int_data(group->data);
+	long val;
+	int ret;
+
+	ret = kstrtol(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	ret = data->write(group->dev, data->group.id, val);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static ssize_t
+str_group_show(struct kobject *kobj, struct fwat_attribute *attr, char *buf)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_str_data *data = to_fwat_str_data(group->data);
+	const char *val;
+	long len;
+	int ret;
+
+	/* show_override does not affect current_value */
+	if (data->group.show_override && attr->type != fwat_bool_current_value)
+		return data->group.show_override(group->dev, attr->type, buf);
+
+	switch (attr->type) {
+	case fwat_str_current_value:
+		ret = data->read(group->dev, data->group.id, &val);
+		if (ret < 0)
+			return ret;
+		break;
+	case fwat_str_default_value:
+		val = data->default_val;
+		break;
+	case fwat_str_min_length:
+		len = data->min_len;
+		return sysfs_emit(buf, "%ld\n", len);
+	case fwat_str_max_length:
+		len = data->max_len;
+		return sysfs_emit(buf, "%ld\n", len);
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return sysfs_emit(buf, "%s\n", val);
+}
+
+static ssize_t
+str_group_store(struct kobject *kobj, struct fwat_attribute *attr, const char *buf,
+		size_t count)
+{
+	const struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_str_data *data = to_fwat_str_data(group->data);
+	int ret;
+
+	ret = data->write(group->dev, data->group.id, buf);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+FWAT_ATTR_RO(all, display_name, display_name_show, FWAT_TYPE_NONE);
+FWAT_ATTR_RO(all, display_name_language_code, display_name_language_code_show, FWAT_TYPE_NONE);
+
+FWAT_ATTR_RO(bool, type, type_show, fwat_group_boolean);
+FWAT_ATTR_RW(bool, current_value, bool_group_show, bool_group_store, fwat_bool_current_value);
+FWAT_ATTR_RO(bool, default_value, bool_group_show, fwat_bool_default_value);
+
+FWAT_ATTR_RO(enum, type, type_show, fwat_group_enumeration);
+FWAT_ATTR_RW(enum, current_value, enum_group_show, enum_group_store, fwat_enum_current_value);
+FWAT_ATTR_RO(enum, default_value, enum_group_show, fwat_enum_default_value);
+FWAT_ATTR_RO(enum, possible_values, enum_group_show, fwat_enum_possible_values);
+
+FWAT_ATTR_RO(int, type, type_show, fwat_group_integer);
+FWAT_ATTR_RW(int, current_value, int_group_show, int_group_store, fwat_int_current_value);
+FWAT_ATTR_RO(int, default_value, int_group_show, fwat_int_default_value);
+FWAT_ATTR_RO(int, min_value, int_group_show, fwat_int_min_value);
+FWAT_ATTR_RO(int, max_value, int_group_show, fwat_int_max_value);
+FWAT_ATTR_RO(int, scalar_increment, int_group_show, fwat_int_scalar_increment);
+
+FWAT_ATTR_RO(str, type, type_show, fwat_group_string);
+FWAT_ATTR_RW(str, current_value, str_group_show, str_group_store, fwat_int_current_value);
+FWAT_ATTR_RO(str, default_value, str_group_show, fwat_str_default_value);
+FWAT_ATTR_RO(str, min_length, str_group_show, fwat_str_min_length);
+FWAT_ATTR_RO(str, max_length, str_group_show, fwat_str_max_length);
+
+static struct attribute *fwat_bool_attrs[] = {
+	&fwat_bool_type_attr.attr,
+	&fwat_all_display_name_attr.attr,
+	&fwat_all_display_name_language_code_attr.attr,
+	&fwat_bool_current_value_attr.attr,
+	&fwat_bool_default_value_attr.attr,
+	NULL
+};
+
+static struct attribute *fwat_enum_attrs[] = {
+	&fwat_enum_type_attr.attr,
+	&fwat_all_display_name_attr.attr,
+	&fwat_all_display_name_language_code_attr.attr,
+	&fwat_enum_current_value_attr.attr,
+	&fwat_enum_default_value_attr.attr,
+	&fwat_enum_possible_values_attr.attr,
+	NULL
+};
+
+static struct attribute *fwat_int_attrs[] = {
+	&fwat_int_type_attr.attr,
+	&fwat_all_display_name_attr.attr,
+	&fwat_all_display_name_language_code_attr.attr,
+	&fwat_int_current_value_attr.attr,
+	&fwat_int_default_value_attr.attr,
+	&fwat_int_min_value_attr.attr,
+	&fwat_int_max_value_attr.attr,
+	&fwat_int_scalar_increment_attr.attr,
+	NULL
+};
+
+static struct attribute *fwat_str_attrs[] = {
+	&fwat_str_type_attr.attr,
+	&fwat_all_display_name_attr.attr,
+	&fwat_all_display_name_language_code_attr.attr,
+	&fwat_str_current_value_attr.attr,
+	&fwat_str_default_value_attr.attr,
+	&fwat_str_min_length_attr.attr,
+	&fwat_str_max_length_attr.attr,
+	NULL
+};
+
+static umode_t fwat_attr_visible(struct kobject *kobj, struct attribute *attr, int n)
+{
+	struct fwat_attribute *fwat_attr = to_fwat_attribute(attr);
+	struct fwat_group *group = kobj_to_fwat_group(kobj);
+	const struct fwat_group_data *data = group->data;
+
+	/* The `type` attribute is always first */
+	if (n == 0)
+		return attr->mode;
+
+	if (attr == &fwat_all_display_name_attr.attr)
+		return data->display_name ? attr->mode : 0;
+
+	if (attr == &fwat_all_display_name_language_code_attr.attr)
+		return data->language_code ? attr->mode : 0;
+
+	/* The `current_value` attribute always has type == 0 */
+	if (!fwat_attr->type)
+		return data->mode;
+
+	return test_bit(fwat_attr->type, &data->fattrs) ? attr->mode : 0;
+}
+
+static umode_t fwat_group_visible(struct kobject *kobj)
+{
+	return true;
+}
+
+DEFINE_SYSFS_GROUP_VISIBLE(fwat);
+
+static const struct attribute_group fwat_bool_group = {
+	.attrs = fwat_bool_attrs,
+	.is_visible = SYSFS_GROUP_VISIBLE(fwat),
+};
+__ATTRIBUTE_GROUPS(fwat_bool);
+
+static const struct attribute_group fwat_enum_group = {
+	.attrs = fwat_enum_attrs,
+	.is_visible = SYSFS_GROUP_VISIBLE(fwat),
+};
+__ATTRIBUTE_GROUPS(fwat_enum);
+
+static const struct attribute_group fwat_int_group = {
+	.attrs = fwat_int_attrs,
+	.is_visible = SYSFS_GROUP_VISIBLE(fwat),
+};
+__ATTRIBUTE_GROUPS(fwat_int);
+
+static const struct attribute_group fwat_str_group = {
+	.attrs = fwat_str_attrs,
+	.is_visible = SYSFS_GROUP_VISIBLE(fwat),
+};
+__ATTRIBUTE_GROUPS(fwat_str);
+
+static ssize_t
+fwat_attr_sysfs_show(struct kobject *kobj, struct attribute *attr, char *buf)
+{
+	struct fwat_attribute *fwat_attr = to_fwat_attribute(attr);
+
+	if (!fwat_attr->show)
+		return -EOPNOTSUPP;
+
+	return fwat_attr->show(kobj, fwat_attr, buf);
+}
+
+static ssize_t
+fwat_attr_sysfs_store(struct kobject *kobj, struct attribute *attr, const char *buf,
+		      size_t count)
+{
+	struct fwat_attribute *fwat_attr = to_fwat_attribute(attr);
+
+	if (!fwat_attr->show)
+		return -EOPNOTSUPP;
+
+	return fwat_attr->store(kobj, fwat_attr, buf, count);
+}
+
+static void fwat_group_release(struct kobject *kobj)
+{
+	struct fwat_group *group = kobj_to_fwat_group(kobj);
+
+	kfree(group);
+}
+
+static const struct sysfs_ops fwat_attr_sysfs_ops = {
+	.show = fwat_attr_sysfs_show,
+	.store = fwat_attr_sysfs_store,
+};
+
+static const struct kobj_type fwat_boolean_ktype = {
+	.sysfs_ops = &fwat_attr_sysfs_ops,
+	.release = fwat_group_release,
+	.default_groups = fwat_bool_groups,
+};
+
+static const struct kobj_type fwat_enumeration_ktype = {
+	.sysfs_ops = &fwat_attr_sysfs_ops,
+	.release = fwat_group_release,
+	.default_groups = fwat_enum_groups,
+};
+
+static const struct kobj_type fwat_integer_ktype = {
+	.sysfs_ops = &fwat_attr_sysfs_ops,
+	.release = fwat_group_release,
+	.default_groups = fwat_int_groups,
+};
+
+static const struct kobj_type fwat_string_ktype = {
+	.sysfs_ops = &fwat_attr_sysfs_ops,
+	.release = fwat_group_release,
+	.default_groups = fwat_str_groups,
+};
+
+static int __fwat_create_group(struct fwat_device *fadev, const struct kobj_type *ktype,
+			       const struct fwat_group_data *data)
+{
+	struct fwat_group *group;
+	int ret;
+
+	group = kzalloc(sizeof(*group), GFP_KERNEL);
+	if (!group)
+		return -ENOMEM;
+
+	group->dev = &fadev->dev;
+	group->data = data;
+
+	group->kobj.kset = fadev->attrs_kset;
+	ret = kobject_init_and_add(&group->kobj, ktype, NULL, "%s", data->name);
+	if (ret) {
+		kobject_put(&group->kobj);
+		return ret;
+	}
+
+	kobject_uevent(&group->kobj, KOBJ_ADD);
+
+	return 0;
+}
+
+static void fwat_remove_auto_groups(struct fwat_device *fadev)
+{
+	struct kobject *pos, *n;
+
+	list_for_each_entry_safe(pos, n, &fadev->attrs_kset->list, entry)
+		kobject_put(pos);
+}
+
+int fwat_create_bool_group(struct fwat_device *fadev, const struct fwat_bool_data *data)
+{
+	return __fwat_create_group(fadev, &fwat_boolean_ktype, &data->group);
+}
+EXPORT_SYMBOL_GPL(fwat_create_bool_group);
+
+int fwat_create_enum_group(struct fwat_device *fadev, const struct fwat_enum_data *data)
+{
+	return __fwat_create_group(fadev, &fwat_enumeration_ktype, &data->group);
+}
+EXPORT_SYMBOL_GPL(fwat_create_enum_group);
+
+int fwat_create_int_group(struct fwat_device *fadev, const struct fwat_int_data *data)
+{
+	return __fwat_create_group(fadev, &fwat_integer_ktype, &data->group);
+}
+EXPORT_SYMBOL_GPL(fwat_create_int_group);
+
+int fwat_create_str_group(struct fwat_device *fadev, const struct fwat_str_data *data)
+{
+	return __fwat_create_group(fadev, &fwat_string_ktype, &data->group);
+}
+EXPORT_SYMBOL_GPL(fwat_create_str_group);
+
 /**
  * fwat_device_register - Create and register a firmware-attributes class
  *			  device
@@ -89,6 +620,7 @@ void fwat_device_unregister(struct fwat_device *fadev)
 	if (!fadev)
 		return;
 
+	fwat_remove_auto_groups(fadev);
 	sysfs_remove_groups(&fadev->attrs_kset->kobj, fadev->groups);
 	kset_unregister(fadev->attrs_kset);
 	device_unregister(&fadev->dev);
diff --git a/drivers/platform/x86/firmware_attributes_class.h b/drivers/platform/x86/firmware_attributes_class.h
index 4ae700eec1e586e1f9ed96bd6e3843342381816d..744fc9ef6055e466caa30b3bc8e23097f8f2dd58 100644
--- a/drivers/platform/x86/firmware_attributes_class.h
+++ b/drivers/platform/x86/firmware_attributes_class.h
@@ -10,6 +10,7 @@
 #include <linux/device/class.h>
 #include <linux/kobject.h>
 #include <linux/sysfs.h>
+#include <linux/list.h>
 
 extern const struct class firmware_attributes_class;
 
@@ -27,6 +28,340 @@ struct fwat_device {
 
 #define to_fwat_device(_d)	container_of_const(_d, struct fwat_device, dev)
 
+enum fwat_group_type {
+	fwat_group_boolean,
+	fwat_group_enumeration,
+	fwat_group_integer,
+	fwat_group_string,
+};
+
+enum fwat_bool_attrs {
+	fwat_bool_current_value,
+	fwat_bool_default_value,
+	fwat_bool_attrs_last
+};
+
+#define FWAT_BOOL_CURRENT_VALUE			BIT(fwat_bool_current_value)
+#define FWAT_BOOL_DEFAULT_VALUE			BIT(fwat_bool_default_value)
+#define FWAT_BOOL_ALL_ATTRS			GENMASK(fwat_bool_attrs_last, 0)
+
+enum fwat_enum_attrs {
+	fwat_enum_current_value,
+	fwat_enum_default_value,
+	fwat_enum_possible_values,
+	fwat_enum_attrs_last
+};
+
+#define FWAT_ENUM_CURRENT_VALUE			BIT(fwat_enum_current_value)
+#define FWAT_ENUM_DEFAULT_VALUE			BIT(fwat_enum_default_value)
+#define FWAT_ENUM_POSSIBLE_VALUES		BIT(fwat_enum_possible_values)
+#define FWAT_ENUM_ALL_ATTRS			GENMASK(fwat_enum_attrs_last, 0)
+
+enum fwat_int_attrs {
+	fwat_int_current_value,
+	fwat_int_default_value,
+	fwat_int_min_value,
+	fwat_int_max_value,
+	fwat_int_scalar_increment,
+	fwat_int_attrs_last
+};
+
+#define FWAT_INT_CURRENT_VALUE			BIT(fwat_int_current_value)
+#define FWAT_INT_DEFAULT_VALUE			BIT(fwat_int_default_value)
+#define FWAT_INT_MIN_VALUE			BIT(fwat_int_min_value)
+#define FWAT_INT_MAX_VALUE			BIT(fwat_int_max_value)
+#define FWAT_INT_SCALAR_INCREMENT		BIT(fwat_int_scalar_increment)
+#define FWAT_INT_ALL_ATTRS			GENMASK(fwat_int_attrs_last, 0)
+
+enum fwat_str_attrs {
+	fwat_str_current_value,
+	fwat_str_default_value,
+	fwat_str_min_length,
+	fwat_str_max_length,
+	fwat_str_attrs_last
+};
+
+#define FWAT_STR_CURRENT_VALUE			BIT(fwat_str_current_value)
+#define FWAT_STR_DEFAULT_VALUE			BIT(fwat_str_default_value)
+#define FWAT_STR_MIN_LENGTH			BIT(fwat_str_min_length)
+#define FWAT_STR_MAX_LENGTH			BIT(fwat_str_max_length)
+#define FWAT_STR_ALL_ATTRS			GENMASK(fwat_str_attrs_last, 0)
+
+static_assert(fwat_bool_current_value == 0);
+static_assert(fwat_enum_current_value == 0);
+static_assert(fwat_int_current_value == 0);
+static_assert(fwat_str_current_value == 0);
+
+/**
+ * struct fwat_group_data - Data struct common between group types
+ * @id: Group ID defined by the user.
+ * @name: Name of the group.
+ * @display_name: Name showed in the display_name attribute. (Optional)
+ * @language_code: Language code showed in the display_name_language_code
+ *                 attribute. (Optional)
+ * @mode: Mode for the current_value attribute. All other attributes will have
+ *        0444 permissions.
+ * @fattrs: Bitmap of selected attributes for this group type.
+ * @show_override: Custom show method for attributes in this group, except for
+ *		   the current_value attribute, for which the a `read` callback
+ *		   will still be used. (Optional)
+ *
+ * NOTE: This struct is not meant to be defined directly. It is supposed to be
+ * embedded and defined as part of fwat_[type]_data structs.
+ */
+struct fwat_group_data {
+	long id;
+	umode_t mode;
+	const char *name;
+	const char *display_name;
+	const char *language_code;
+	unsigned long fattrs;
+	ssize_t (*show_override)(struct device *dev, int type, char *buf);
+};
+
+/**
+ * struct fwat_bool_data - Data struct for the boolean group type
+ * @read: Read callback for the current_value attribute.
+ * @write: Write callback for the current_value attribute.
+ * @default_val: Default value.
+ * @group: Group data.
+ */
+struct fwat_bool_data {
+	int (*read)(struct device *dev, long id, bool *val);
+	int (*write)(struct device *dev, long id, bool val);
+	bool default_val;
+	struct fwat_group_data group;
+};
+
+/**
+ * struct fwat_enum_data - Data struct for the enumeration group type
+ * @read: Read callback for the current_value attribute.
+ * @write: Write callback for the current_value attribute.
+ * @default_idx: Index of the default value in the @possible_vals array.
+ * @possible_vals: Array of possible value strings for this group type.
+ * @group: Group data.
+ *
+ * NOTE: The `val_idx` argument in the @write callback is guaranteed to be a
+ *       valid (within bounds) index. However, the user is in charge of writing
+ *       valid indexes to the `*val_idx` argument of the @read callback.
+ *       Failing to do so may result in an OOB access.
+ */
+struct fwat_enum_data {
+	int (*read)(struct device *dev, long id, int *val_idx);
+	int (*write)(struct device *dev, long id, int val_idx);
+	int default_idx;
+	const char * const *possible_vals;
+	struct fwat_group_data group;
+};
+
+/**
+ * struct fwat_int_data - Data struct for the integer group type
+ * @read: Read callback for the current_value attribute.
+ * @write: Write callback for the current_value attribute.
+ * @default_val: Default value.
+ * @min_val: Minimum value.
+ * @max_val: Maximum value.
+ * @increment: Scalar increment for this value.
+ * @group: Group data.
+ *
+ * NOTE: The @min_val, @max_val, @increment constraints are merely informative.
+ *       These values are not enforced in any of the callbacks.
+ */
+struct fwat_int_data {
+	int (*read)(struct device *dev, long id, long *val);
+	int (*write)(struct device *dev, long id, long val);
+	long default_val;
+	long min_val;
+	long max_val;
+	long increment;
+	struct fwat_group_data group;
+};
+
+/**
+ * struct fwat_str_data - Data struct for the string group type
+ * @read: Read callback for the current_value attribute.
+ * @write: Write callback for the current_value attribute.
+ * @default_val: Default value.
+ * @min_len: Minimum string length.
+ * @max_len: Maximum string length.
+ * @group: Group data.
+ *
+ * NOTE: The @min_len, @max_len constraints are merely informative. These
+ *       values are not enforced in any of the callbacks.
+ */
+struct fwat_str_data {
+	int (*read)(struct device *dev, long id, const char **buf);
+	int (*write)(struct device *dev, long id, const char *buf);
+	const char *default_val;
+	long min_len;
+	long max_len;
+	struct fwat_group_data group;
+};
+
+#define __FWAT_GROUP(_name, _disp_name, _mode, _fattrs) \
+	{ .name = __stringify(_name), .display_name = _disp_name, .mode = _mode, .fattrs = _fattrs }
+
+/**
+ * DEFINE_FWAT_BOOL_GROUP - Convenience macro to quickly define an static
+ *                          struct fwat_bool_data instance
+ * @_name: Name of the group.
+ * @_disp_name: Name showed in the display_name attribute. (Optional)
+ * @_def_val: Default value.
+ * @_mode: Mode for the current_value attribute. All other attributes will have
+ *         0444 permissions.
+ * @_fattrs: Bitmap of selected attributes for this group type.
+ *
+ * `read` and `write` callbacks are required to be already defined as
+ * `_name##_read` and `_name##_write` respectively.
+ */
+#define DEFINE_FWAT_BOOL_GROUP(_name, _disp_name, _def_val, _mode, _fattrs) \
+	static const struct fwat_bool_data _name##_group_data = {	\
+		.read = _name##_read,					\
+		.write = _name##_write,					\
+		.default_val = _def_val,				\
+		.group = __FWAT_GROUP(_name, _disp_name, _mode, _fattrs), \
+	}
+
+/**
+ * DEFINE_FWAT_ENUM_GROUP - Convenience macro to quickly define an static
+ *                          struct fwat_enum_data instance
+ * @_name: Name of the group.
+ * @_disp_name: Name showed in the display_name attribute. (Optional)
+ * @_def_idx: Index of the default value in the @_poss_vals array.
+ * @_poss_vals: Array of possible value strings for this group type.
+ * @_mode: Mode for the current_value attribute. All other attributes will have
+ *         0444 permissions.
+ * @_fattrs: Bitmap of selected attributes for this group type.
+ *
+ * `read` and `write` callbacks are required to be already defined as
+ * `_name##_read` and `_name##_write` respectively.
+ *
+ * NOTE: The `val_idx` argument in the `write` callback is guaranteed to be a
+ *       valid (within bounds) index. However, the user is in charge of writing
+ *       valid indexes to the `*val_idx` argument of the `read` callback.
+ *       Failing to do so may result in an OOB access.
+ */
+#define DEFINE_FWAT_ENUM_GROUP(_name, _disp_name, _poss_vals, _def_idx, _mode, _fattrs) \
+	static const struct fwat_enum_data _name##_group_data = {	\
+		.read = _name##_read,					\
+		.write = _name##_write,					\
+		.default_idx = _def_idx,				\
+		.possible_vals = _poss_vals,				\
+		.group = __FWAT_GROUP(_name, _disp_name, _mode, _fattrs), \
+	}
+
+/**
+ * DEFINE_FWAT_INT_GROUP - Convenience macro to quickly define an static
+ *                         struct fwat_int_data instance
+ * @_name: Name of the group.
+ * @_disp_name: Name showed in the display_name attribute. (Optional)
+ * @_def_val: Default value.
+ * @_min: Minimum value.
+ * @_max: Maximum value.
+ * @_inc: Scalar increment for this value.
+ * @_mode: Mode for the current_value attribute. All other attributes will have
+ *         0444 permissions.
+ * @_fattrs: Bitmap of selected attributes for this group type.
+ *
+ * `read` and `write` callbacks are required to be already defined as
+ * `_name##_read` and `_name##_write` respectively.
+ *
+ * NOTE: The @_min, @_max, @_inc constraints are merely informative. These
+ *       values are not enforced in any of the callbacks.
+ */
+#define DEFINE_FWAT_INT_GROUP(_name, _disp_name, _def_val, _min, _max, _inc, _mode, _fattrs) \
+	static const struct fwat_int_data _name##_group_data = {	\
+		.read = _name##_read,					\
+		.write = _name##_write,					\
+		.default_val = _def_val,				\
+		.min_val = _min,					\
+		.max_val = _max,					\
+		.increment = _inc,					\
+		.group = __FWAT_GROUP(_name, _disp_name, _mode, _fattrs), \
+	}
+
+/**
+ * DEFINE_FWAT_STR_GROUP - Convenience macro to quickly define an static
+ *                         struct fwat_str_data instance
+ * @_name: Name of the group.
+ * @_disp_name: Name showed in the display_name attribute. (Optional)
+ * @_def_val: Default value.
+ * @_min: Minimum string length.
+ * @_max: Maximum string length.
+ * @_mode: Mode for the current_value attribute. All other attributes will have
+ *         0444 permissions.
+ * @_fattrs: Bitmap of selected attributes for this group type.
+ *
+ * `read` and `write` callbacks are required to be already defined as
+ * `_name##_read` and `_name##_write` respectively.
+ *
+ * NOTE: The @_min, @_max constraints are merely informative. These values are
+ *       not enforced in any of the callbacks.
+ */
+#define DEFINE_FWAT_STR_GROUP(_name, _disp_name, _def_val, _min, _max, _mode, _fattrs) \
+	static const struct fwat_str_data _name##_group_data = {	\
+		.read = _name##_read,					\
+		.write = _name##_write,					\
+		.default_val = _def_val,				\
+		.min_len = _min,					\
+		.max_len = _max,					\
+		.group = __FWAT_GROUP(_name, _disp_name, _mode, _fattrs), \
+	}
+
+int fwat_create_bool_group(struct fwat_device *fadev,
+			   const struct fwat_bool_data *data);
+int fwat_create_enum_group(struct fwat_device *fadev,
+			   const struct fwat_enum_data *data);
+int fwat_create_int_group(struct fwat_device *fadev,
+			  const struct fwat_int_data *data);
+int fwat_create_str_group(struct fwat_device *fadev,
+			  const struct fwat_str_data *data);
+
+/**
+ * fwat_create_group - Convenience generic macro to create a group
+ * @_dev: fwat_device
+ * @_data: One of fwat_{bool,enum,int,str}_data instance
+ *
+ * This macro (and associated functions) creates a sysfs group under the
+ * 'attributes' directory, which is located in the class device root directory.
+ *
+ * See Documentation/ABI/testing/sysfs-class-firmware-attributes for details.
+ *
+ * The @_data associated with this group may be created either statically,
+ * through DEFINE_FWAT_*_GROUP macros or dynamically, in which case the user
+ * would have allocate and fill the struct manually. The dynamic approach should
+ * be preferred when group constraints and/or visibility is decided dynamically.
+ *
+ * Example:
+ *
+ * static int stat_read(...){...};
+ * static int stat_write(...){...};
+ *
+ * DEFINE_FWAT_(BOOL|ENUM|INT|STR)_GROUP(stat, ...);
+ *
+ * static int create_groups(struct fwat_device *fadev)
+ * {
+ *	struct fwat_enum_data *dyn_group_data;
+ *
+ *	dyn_group_data = kzalloc(...);
+ *	// Fill the data
+ *	...
+ *	fwat_create_group(fadev, &stat_group_data);
+ *	fwat_create_group(fadev, &dyn_group_data);
+ *	fwat_create_group(...);
+ *	...
+ * }
+ *
+ * Return: 0 on success, -errno on failure
+ */
+#define fwat_create_group(_dev, _data) \
+	_Generic((_data),							\
+		 const struct fwat_bool_data * : fwat_create_bool_group,	\
+		 const struct fwat_enum_data * : fwat_create_enum_group,	\
+		 const struct fwat_int_data * : fwat_create_int_group,		\
+		 const struct fwat_str_data * : fwat_create_str_group)		\
+		(_dev, _data)
+
 struct fwat_device * __must_check
 fwat_device_register(struct device *parent, const char *name, void *data,
 		     const struct attribute_group **groups);

-- 
2.50.0