Message-Id: <D9RW7Y6IU7Y0.GOM8TXTY9QPA@gmail.com>
Date: Fri, 09 May 2025 16:56:33 -0300
From: "Kurt Borja" <kuurtb@...il.com>
To: "Mario Limonciello" <mario.limonciello@....com>, "Hans de Goede"
 <hdegoede@...hat.com>, Ilpo Järvinen
 <ilpo.jarvinen@...ux.intel.com>, Thomas Weißschuh
 <linux@...ssschuh.net>, "Joshua Grisham" <josh@...huagrisham.com>, "Mark
 Pearson" <mpearson-lenovo@...ebb.ca>, "Armin Wolf" <W_Armin@....de>
Cc: "Antheas Kapenekakis" <lkml@...heas.dev>, "Derek J. Clark"
 <derekjohn.clark@...il.com>, "Prasanth Ksr" <prasanth.ksr@...l.com>, "Jorge
 Lopez" <jorge.lopez2@...com>, <platform-driver-x86@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <Dell.Client.Kernel@...l.com>
Subject: Re: [PATCH RFC 2/5] platform/x86: firmware_attributes_class: Add a
 high level API

Hi Mario,

On Fri May 9, 2025 at 12:58 PM -03, Mario Limonciello wrote:
> On 5/9/2025 2:48 AM, Kurt Borja wrote:
>> Add an attribute configuration mechanism through the newly introduced
>> `struct fwat_dev_config`, which makes use of other documented structs
>> and callbacks.
>> 
>> This API aims to be simple, yet flexible. In order to accomplish this,
>> the following features were taken into account:
>> 
>> * Ability to statically define attributes
>> * Custom read/write callbacks for each attribute type
>> * Ability to map attributes to numbers in order to differentiate them in
>>    callbacks (`aux` number)
>> * Ability to reuse read/write callbacks in different attributes
>> * Ability to reuse property selection in different attributes
>> * Optional visibility callback for dynamic attribute visibility
>> 
>> Signed-off-by: Kurt Borja <kuurtb@...il.com>
>> ---
>>   drivers/platform/x86/firmware_attributes_class.c | 249 ++++++++++++++++++++++-
>>   drivers/platform/x86/firmware_attributes_class.h | 228 +++++++++++++++++++++
>>   2 files changed, 474 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/platform/x86/firmware_attributes_class.c b/drivers/platform/x86/firmware_attributes_class.c
>> index 58ab1495ba3bd449cfe17de2827a57a0c5937788..7cfb0f49f235728c7450a82a7e9d00b8963d3dea 100644
>> --- a/drivers/platform/x86/firmware_attributes_class.c
>> +++ b/drivers/platform/x86/firmware_attributes_class.c
>> @@ -7,14 +7,233 @@
>>   #include <linux/kobject.h>
>>   #include <linux/module.h>
>>   #include <linux/slab.h>
>> +#include <linux/sysfs.h>
>>   #include <linux/types.h>
>>   #include "firmware_attributes_class.h"
>>   
>> +#define to_fwat_attribute_ext(_a) container_of_const(_a, struct fwat_attribute_ext, attr)
>> +
>> +struct fwat_attribute_ext {
>> +	struct fwat_attribute attr;
>> +	enum fwat_property prop;
>> +	const struct fwat_attr_config *config;
>> +};
>> +
>>   const struct class firmware_attributes_class = {
>>   	.name = "firmware-attributes",
>>   };
>>   EXPORT_SYMBOL_GPL(firmware_attributes_class);
>>   
>> +static const char * const fwat_type_labels[] = {
>> +	[fwat_type_integer]		= "integer",
>> +	[fwat_type_string]		= "string",
>> +	[fwat_type_enumeration]		= "enumeration",
>> +};
>> +
>> +static const char * const fwat_prop_labels[] = {
>> +	[FWAT_PROP_DISPLAY_NAME]		= "display_name",
>> +	[FWAT_PROP_LANGUAGE_CODE]		= "display_name_language_code",
>> +	[FWAT_PROP_DEFAULT]			= "default",
>> +
>> +	[FWAT_INT_PROP_MIN]			= "min_value",
>> +	[FWAT_INT_PROP_MAX]			= "max_value",
>> +	[FWAT_INT_PROP_INCREMENT]		= "scalar_increment",
>> +
>> +	[FWAT_STR_PROP_MIN]			= "min_length",
>> +	[FWAT_STR_PROP_MAX]			= "max_length",
>> +
>> +	[FWAT_ENUM_PROP_POSSIBLE_VALUES]	= "possible_values",
>> +};
>> +
>> +static ssize_t
>> +fwat_type_show(struct device *dev, const struct fwat_attribute *attr, char *buf)
>> +{
>> +	const struct fwat_attribute_ext *ext = to_fwat_attribute_ext(attr);
>> +	const struct fwat_attr_config *config = ext->config;
>> +
>> +	return sysfs_emit(buf, "%s\n", fwat_type_labels[config->type]);
>> +}
>> +
>> +static ssize_t
>> +fwat_property_show(struct device *dev, const struct fwat_attribute *attr, char *buf)
>> +{
>> +	const struct fwat_attribute_ext *ext = to_fwat_attribute_ext(attr);
>> +	const struct fwat_attr_config *config = ext->config;
>> +
>> +	if (!config->ops->prop_read)
>> +		return -EOPNOTSUPP;
>> +
>> +	return config->ops->prop_read(dev, config->aux, ext->prop, buf);
>> +}
>> +
>> +static ssize_t
>> +fwat_current_value_show(struct device *dev, const struct fwat_attribute *attr, char *buf)
>> +{
>> +	const struct fwat_attribute_ext *ext = to_fwat_attribute_ext(attr);
>> +	const struct fwat_attr_config *config = ext->config;
>> +	const char *str;
>> +	long int_val;
>> +	int ret;
>> +
>> +	switch (config->type) {
>> +	case fwat_type_integer:
>> +		ret = config->ops->integer_read(dev, config->aux, &int_val);
>> +		if (ret)
>> +			return ret;
>> +
>> +		return sysfs_emit(buf, "%ld\n", int_val);
>> +	case fwat_type_string:
>> +		ret = config->ops->string_read(dev, config->aux, &str);
>> +		if (ret)
>> +			return ret;
>> +
>> +		return sysfs_emit(buf, "%s\n", str);
>> +	case fwat_type_enumeration:
>> +		ret = config->ops->enumeration_read(dev, config->aux, &str);
>> +		if (ret)
>> +			return ret;
>> +
>> +		return sysfs_emit(buf, "%s\n", str);
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +}
>> +
>> +static ssize_t
>> +fwat_current_value_store(struct device *dev, const struct fwat_attribute *attr,
>> +			 const char *buf, size_t count)
>> +{
>> +	const struct fwat_attribute_ext *ext = to_fwat_attribute_ext(attr);
>> +	const struct fwat_attr_config *config = ext->config;
>> +	long int_val;
>> +	int ret;
>> +
>> +	switch (config->type) {
>> +	case fwat_type_integer:
>> +		ret = kstrtol(buf, 0, &int_val);
>> +		if (ret)
>> +			return ret;
>> +
>> +		ret = config->ops->integer_write(dev, config->aux, int_val);
>> +		break;
>> +	case fwat_type_string:
>> +		ret = config->ops->string_write(dev, config->aux, buf);
>> +		break;
>> +	case fwat_type_enumeration:
>> +		ret = config->ops->enumeration_write(dev, config->aux, buf);
>> +		break;
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +
>> +	return ret ? ret : count;
>> +}
>> +
>> +static struct attribute *
>> +fwat_alloc_attr(struct device *dev, const struct fwat_attr_config *config,
>> +		const char *attr_name, umode_t mode, enum fwat_property prop,
>> +		ssize_t (*show)(struct device *dev, const struct fwat_attribute *attr,
>> +				char *buf),
>> +		ssize_t (*store)(struct device *dev, const struct fwat_attribute *attr,
>> +				 const char *buf, size_t count))
>> +{
>> +	struct fwat_attribute_ext *fattr;
>> +
>> +	fattr = devm_kzalloc(dev, sizeof(*fattr), GFP_KERNEL);
>> +	if (!fattr)
>> +		return NULL;
>> +
>> +	fattr->attr.attr.name = attr_name;
>> +	fattr->attr.attr.mode = mode;
>> +	fattr->attr.show = show;
>> +	fattr->attr.store = store;
>> +	fattr->prop = prop;
>> +	fattr->config = config;
>> +	sysfs_attr_init(&fattr->attr.attr);
>> +
>> +	return &fattr->attr.attr;
>> +}
>> +
>> +static struct attribute **
>> +fwat_create_attrs(struct device *dev, const struct fwat_attr_config *config)
>> +{
>> +	struct attribute **attrs;
>> +	enum fwat_property prop;
>> +	unsigned int index = 0;
>> +
>> +	attrs = devm_kcalloc(dev, config->num_props + 3, sizeof(*attrs), GFP_KERNEL);
>> +	if (!attrs)
>> +		return NULL;
>> +
>> +	/*
>> +	 * Create optional attributes
>> +	 */
> Just a nit here; this probably doesn't need to be a multiline comment. 
> a single line like this is fine:
>
> /* optional attributes */
>
>> +	for (; index < config->num_props; index++) {
>> +		prop = config->props[index];
>> +		attrs[index] = fwat_alloc_attr(dev, config, fwat_prop_labels[prop],
>> +					       0444, prop, fwat_property_show, NULL);
>> +	}
>> +
>> +	/*
>> +	 * Create mandatory attributes
>> +	 */
>
> Same as above

Ack for these two.

>
>> +	attrs[index++] = fwat_alloc_attr(dev, config, "type", 0444, 0, fwat_type_show, NULL);
>> +	attrs[index++] = fwat_alloc_attr(dev, config, "current_value", 0644, 0,
>
> Is this permission right?  Some attributes could be considered more 
> sensitive can't they?

You are right. I assumed most drivers would want 0644 but think-lmi and
dell sysman use 0600.

I can add a mode_t mask to fwat_attr_config and use that for
current_value, while other properties would be masked by it, i.e.
`0444 & config->mode`

What do you think?

-- 
 ~ Kurt

>
>> +					 fwat_current_value_show, fwat_current_value_store);
>> +
>> +	return attrs;
>> +}
>> +
>> +static const struct attribute_group *
>> +fwat_create_group(struct device *dev, const struct fwat_attr_config *config)
>> +{
>> +	struct attribute_group *group;
>> +	struct attribute **attrs;
>> +
>> +	group = devm_kzalloc(dev, sizeof(*group), GFP_KERNEL);
>> +	if (!group)
>> +		return NULL;
>> +
>> +	attrs = fwat_create_attrs(dev, config);
>> +	if (!attrs)
>> +		return NULL;
>> +
>> +	group->name = config->name;
>> +	group->attrs = attrs;
>> +
>> +	return group;
>> +}
>> +
>> +static const struct attribute_group **
>> +fwat_create_auto_groups(struct device *dev, const struct fwat_dev_config *config)
>> +{
>> +	const struct attribute_group **groups;
>> +	const struct attribute_group *grp;
>> +	unsigned int index = 0;
>> +	size_t ngroups = 0;
>> +
>> +	while (config->attrs_config[ngroups])
>> +		ngroups++;
>> +
>> +	groups = devm_kcalloc(dev, ngroups + 1, sizeof(*groups), GFP_KERNEL);
>> +	if (!groups)
>> +		return NULL;
>> +
>> +	for (unsigned int i = 0; i < ngroups; i++) {
>> +		if (config->is_visible &&
>> +		    !config->is_visible(dev, config->attrs_config[i]))
>> +			continue;
>> +
>> +		grp = fwat_create_group(dev, config->attrs_config[i]);
>> +		if (!grp)
>> +			return NULL;
>> +
>> +		groups[index++] = grp;
>> +	}
>> +
>> +	return groups;
>> +}
>> +
>>   static ssize_t fwat_attrs_kobj_show(struct kobject *kobj, struct attribute *attr,
>>   				    char *buf)
>>   {
>> @@ -61,6 +280,7 @@ static const struct kobj_type fwat_attrs_ktype = {
>>    *			  device
>>    * @parent: Parent device
>>    * @name: Name of the class device
>> + * @config: Device configuration
>>    * @data: Drvdata of the class device
>>    * @groups: Sysfs groups for the custom `fwat_attrs_ktype` kobj_type
>>    *
>> @@ -72,8 +292,10 @@ static const struct kobj_type fwat_attrs_ktype = {
>>    */
>>   struct fwat_device *
>>   fwat_device_register(struct device *parent, const char *name, void *data,
>> +		     const struct fwat_dev_config *config,
>>   		     const struct attribute_group **groups)
>>   {
>> +	const struct attribute_group **auto_groups;
>>   	struct fwat_device *fadev;
>>   	struct device *dev;
>>   	int ret;
>> @@ -97,19 +319,36 @@ fwat_device_register(struct device *parent, const char *name, void *data,
>>   	if (ret)
>>   		goto out_kobj_put;
>>   
>> -	if (groups) {
>> -		ret = sysfs_create_groups(&fadev->attrs_kobj, groups);
>> +	if (config) {
>> +		auto_groups = fwat_create_auto_groups(dev, config);
>> +		if (!auto_groups) {
>> +			ret = -ENOMEM;
>> +			goto out_kobj_unregister;
>> +		}
>> +
>> +		ret = sysfs_create_groups(&fadev->attrs_kobj, auto_groups);
>>   		if (ret)
>>   			goto out_kobj_unregister;
>>   	}
>>   
>> +	if (groups) {
>> +		ret = sysfs_create_groups(&fadev->attrs_kobj, groups);
>> +		if (ret)
>> +			goto out_remove_auto_groups;
>> +	}
>> +
>>   	fadev->dev = dev;
>>   	fadev->groups = groups;
>> +	fadev->auto_groups = groups;
>>   
>>   	kobject_uevent(&fadev->attrs_kobj, KOBJ_ADD);
>>   
>>   	return fadev;
>>   
>> +out_remove_auto_groups:
>> +	if (config)
>> +		sysfs_remove_groups(&fadev->attrs_kobj, auto_groups);
>> +
>>   out_kobj_unregister:
>>   	kobject_del(&fadev->attrs_kobj);
>>   
>> @@ -125,6 +364,8 @@ void fwat_device_unregister(struct fwat_device *fwadev)
>>   {
>>   	if (fwadev->groups)
>>   		sysfs_remove_groups(&fwadev->attrs_kobj, fwadev->groups);
>> +	if (fwadev->auto_groups)
>> +		sysfs_remove_groups(&fwadev->attrs_kobj, fwadev->auto_groups);
>>   	kobject_del(&fwadev->attrs_kobj);
>>   	kobject_put(&fwadev->attrs_kobj);
>>   	device_unregister(fwadev->dev);
>> @@ -143,6 +384,7 @@ static void devm_fwat_device_release(void *data)
>>    *			       device
>>    * @parent: Parent device
>>    * @name: Name of the class device
>> + * @config: Device configuration
>>    * @data: Drvdata of the class device
>>    * @groups: Sysfs groups for the custom `fwat_attrs_ktype` kobj_type
>>    *
>> @@ -156,12 +398,13 @@ static void devm_fwat_device_release(void *data)
>>    */
>>   struct fwat_device *
>>   devm_fwat_device_register(struct device *parent, const char *name, void *data,
>> +			  const struct fwat_dev_config *config,
>>   			  const struct attribute_group **groups)
>>   {
>>   	struct fwat_device *fadev;
>>   	int ret;
>>   
>> -	fadev = fwat_device_register(parent, name, data, groups);
>> +	fadev = fwat_device_register(parent, name, data, config, groups);
>>   	if (IS_ERR(fadev))
>>   		return fadev;
>>   
>> diff --git a/drivers/platform/x86/firmware_attributes_class.h b/drivers/platform/x86/firmware_attributes_class.h
>> index ad94bf91e5af30a2b8feb9abf224ee6f0d17600a..f250875d785c3439682c43c693f98e1c20e9ff54 100644
>> --- a/drivers/platform/x86/firmware_attributes_class.h
>> +++ b/drivers/platform/x86/firmware_attributes_class.h
>> @@ -18,11 +18,14 @@ extern const struct class firmware_attributes_class;
>>    * @dev: The class device.
>>    * @attrs_kobj: The "attributes" root kobject.
>>    * @groups: Sysfs groups attached to the @attrs_kobj.
>> + * @auto_groups: Sysgs groups generated from &struct fwat_attr_config attached.
>> + * to the @attrs_kobj
>>    */
>>   struct fwat_device {
>>   	struct device *dev;
>>   	struct kobject attrs_kobj;
>>   	const struct attribute_group **groups;
>> +	const struct attribute_group **auto_groups;
>>   };
>>   
>>   #define to_fwat_device(_k)	container_of_const(_k, struct fwat_device, attrs_kobj)
>> @@ -30,6 +33,7 @@ struct fwat_device {
>>   /**
>>    * struct fwat_attribute - The firmware-attributes's custom attribute
>>    * @attr: Embedded struct attribute.
>> + * @aux: Auxiliary number defined by the user.
>>    * @show: Show method called by the "attributes" kobject's ktype.
>>    * @store: Store method called by the "attributes" kobject's ktype.
>>    */
>> @@ -43,14 +47,238 @@ struct fwat_attribute {
>>   
>>   #define to_fwat_attribute(_a) container_of_const(_a, struct fwat_attribute, attr)
>>   
>> +enum fwat_attr_type {
>> +	fwat_type_integer,
>> +	fwat_type_string,
>> +	fwat_type_enumeration,
>> +};
>> +
>> +enum fwat_property {
>> +	FWAT_PROP_DISPLAY_NAME,
>> +	FWAT_PROP_LANGUAGE_CODE,
>> +	FWAT_PROP_DEFAULT,
>> +
>> +	FWAT_INT_PROP_MIN,
>> +	FWAT_INT_PROP_MAX,
>> +	FWAT_INT_PROP_INCREMENT,
>> +
>> +	FWAT_STR_PROP_MIN,
>> +	FWAT_STR_PROP_MAX,
>> +
>> +	FWAT_ENUM_PROP_POSSIBLE_VALUES,
>> +};
>> +
>> +struct fwat_attr_config;
>> +
>> +/**
>> + * struct fwat_attr_ops - Operations for a firmware *attribute*
>> + * @prop_read: Callback for retrieving each configured property of an attribute.
>> + * @integer_read: Callback for reading the current_value of an attribute of
>> + *                type *integer*.
>> + * @integer_write: Callback for writing the current_value of an attribute of
>> + *                 type *integer*.
>> + * @string_read: Callback for reading the current_value of an attribute of type
>> + *               *string*.
>> + * @string_write: Callback for writing the current_value of an attribute of type
>> + *                *string*.
>> + * @enumeration_read: Callback for reading the current_value of an attribute of
>> + *                    type *enumeration*.
>> + * @enumeration_write: Callback for writing the current_value of an attribute
>> + *                     of type *enumeration*.
>> + */
>> +struct fwat_attr_ops {
>> +	ssize_t (*prop_read)(struct device *dev, long aux,
>> +			     enum fwat_property prop, const char *buf);
>> +	union {
>> +		struct {
>> +			int (*integer_read)(struct device *dev, long aux,
>> +					    long *val);
>> +			int (*integer_write)(struct device *dev, long aux,
>> +					     long val);
>> +		};
>> +		struct {
>> +			int (*string_read)(struct device *dev, long aux,
>> +					   const char **str);
>> +			int (*string_write)(struct device *dev, long aux,
>> +					    const char *str);
>> +		};
>> +		struct {
>> +			int (*enumeration_read)(struct device *dev, long aux,
>> +						const char **str);
>> +			int (*enumeration_write)(struct device *dev, long aux,
>> +						 const char *str);
>> +		};
>> +	};
>> +};
>> +
>> +/**
>> + * struct fwat_attr_config - Configuration for a single firmware *attribute*
>> + * @name: Name of the sysfs group associated with this *attribute*.
>> + * @type: Type of this *attribute*.
>> + * @aux: Auxiliary number defined by the user, which will be passed to
>> + *       read/write callbacks.
>> + * @ops: Operations for this *attribute*.
>> + * @props: Array of properties of this *attribute*.
>> + * @num_props: Size of the props array.
>> + */
>> +struct fwat_attr_config {
>> +	const char *name;
>> +	enum fwat_attr_type type;
>> +	long aux;
>> +	const struct fwat_attr_ops *ops;
>> +	const enum fwat_property *props;
>> +	size_t num_props;
>> +};
>> +
>> +/**
>> + * DEFINE_SIMPLE_FWAT_OPS() - Define static &struct fwat_attr_ops for a simple
>> + *                            *attribute* with no properties, i.e. No
>> + *                            &fwat_attr_ops.read_prop callback
>> + * @_name: Prefix of the `read` and `write` callbacks.
>> + * @_type: Firmware *attribute* type.
>> + *
>> + * Example:
>> + *
>> + * static int example_read(...) {...}
>> + * static int example_write(...) {...}
>> + *
>> + * DEFINE_SIMPLE_FWAT_OPS(example, ...);
>> + */
>> +#define DEFINE_SIMPLE_FWAT_OPS(_name, _type)		\
>> +	static const struct fwat_attr_ops _name##_ops = { \
>> +		._type##_read = _name##_read,		\
>> +		._type##_write = _name##_write,		\
>> +	}
>> +
>> +/**
>> + * DEFINE_FWAT_OPS() - Define static &struct fwat_attr_ops with all callbacks.
>> + * @_name: Prefix of the `read` and `write` callbacks.
>> + * @_type: Firmware *attribute* type.
>> + *
>> + * Example:
>> + *
>> + * static int example_read(...) {...}
>> + * static int example_write(...) {...}
>> + * static int example_prop_read(...) {...}
>> + *
>> + * DEFINE_FWAT_OPS(example, ...);
>> + */
>> +#define DEFINE_FWAT_OPS(_name, _type)			\
>> +	static const struct fwat_attr_ops _name##_ops = { \
>> +		.prop_read = _name##_prop_read,		\
>> +		._type##_read = _name##_read,		\
>> +		._type##_write = _name##_write,		\
>> +	}
>> +
>> +/**
>> + * FWAT_CONFIG() - Configuration pointer for a single firmware *attribute*.
>> + * @_name: String name of this *attribute*.
>> + * @_type: Firmware *attribute* type.
>> + * @_ops: Pointer to &struct fwat_attr_ops.
>> + * @_props: Pointer to a enum fwat_property array.
>> + * @_num_props: Size of the @_props array.
>> + *
>> + * This is a convenience macro to quickly construct a &struct fwat_attr_config
>> + * array, which will be passed to &struct fwat_dev_config.
>> + *
>> + * Example:
>> + *
>> + * static int example_read(...) {...}
>> + * static int example_write(...) {...}
>> + * static int example_prop_read(...) {...}
>> + *
>> + * DEFINE_FWAT_OPS(example, ...);
>> + *
>> + * static const enum fwat_property props[] = {...};
>> + *
>> + * static const struct fwat_attr_config * const attrs_config[] = {
>> + *	FWAT_CONFIG(example, ..., &example_fwat_ops, props,
>> + *		    ARRAY_SIZE(props)),
>> + *	...
>> + *	NULL
>> + * };
>> + *
>> + * static const struct fwat_dev_config fdev_config = {
>> + *	.attrs_config = attrs_config,
>> + *	...
>> + * }
>> + */
>> +#define FWAT_CONFIG(_name, _type, _ops, _props, _num_props) \
>> +	(&(const struct fwat_attr_config) {	\
>> +		.name = _name,				\
>> +		.type = fwat_type_##_type,		\
>> +		.ops = _ops,				\
>> +		.num_props = _num_props,		\
>> +		.props = _props,			\
>> +	})
>> +
>> +/**
>> + * FWAT_CONFIG_AUX() - Configuration pointer for a single firmware *attribute*
>> + *                     with an auxiliary number defined by the user
>> + * @_name: String name of this *attribute*.
>> + * @_type: Firmware *attribute* type.
>> + * @_aux: Auxiliary number defined by the user.
>> + * @_ops: Pointer to &struct fwat_attr_ops.
>> + * @_props: Pointer to a enum fwat_property array.
>> + * @_num_props: Size of the @_props array.
>> + *
>> + * This is a convenience macro to quickly construct a &struct fwat_attr_config
>> + * array, which will be passed to &struct fwat_dev_config.
>> + *
>> + * Example:
>> + *
>> + * static int example_read(...) {...}
>> + * static int example_write(...) {...}
>> + * static int example_prop_read(...) {...}
>> + *
>> + * DEFINE_FWAT_OPS(example, ...);
>> + *
>> + * static const enum fwat_property props[] = {...};
>> + *
>> + * static const struct fwat_attr_config * const config[] = {
>> + *	FWAT_CONFIG_AUX(example, ..., n, &example_fwat_ops, props,
>> + *			ARRAY_SIZE(props)),
>> + *	...
>> + *	NULL
>> + * };
>> + *
>> + * static const struct fwat_dev_config fdev_config = {
>> + *	.attrs_config = attrs_config,
>> + *	...
>> + * }
>> + */
>> +#define FWAT_CONFIG_AUX(_name, _type, _aux, _ops, _props, _num_props) \
>> +	(&(const struct fwat_attr_config) {		\
>> +		.name = _name,				\
>> +		.type = fwat_type_##_type,		\
>> +		.aux = _aux,				\
>> +		.ops = _ops,				\
>> +		.num_props = _num_props,		\
>> +		.props = _props,			\
>> +	})
>> +
>> +/**
>> + * struct fwat_dev_config - Configuration for this devices's
>> + *                          &fwat_device.auto_groups
>> + * @attrs_config: NULL terminated &struct fwat_attr_config array.
>> + * @is_visible: Optional visibility callback to determine the visibility
>> + *              of each auto_group.
>> + */
>> +struct fwat_dev_config {
>> +	const struct fwat_attr_config *const *attrs_config;
>> +	bool (*is_visible)(struct device *dev, const struct fwat_attr_config *config);
>> +};
>> +
>>   struct fwat_device * __must_check
>>   fwat_device_register(struct device *parent, const char *name, void *data,
>> +		     const struct fwat_dev_config *config,
>>   		     const struct attribute_group **groups);
>>   
>>   void fwat_device_unregister(struct fwat_device *fwadev);
>>   
>>   struct fwat_device * __must_check
>>   devm_fwat_device_register(struct device *parent, const char *name, void *data,
>> +			  const struct fwat_dev_config *config,
>>   			  const struct attribute_group **groups);
>>   
>>   #endif /* FW_ATTR_CLASS_H */
>> 


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