Message-Id: <20250517-fw-attrs-api-v2-1-fa1ab045a01c@gmail.com>
Date: Sat, 17 May 2025 05:51:36 -0300
From: Kurt Borja <kuurtb@...il.com>
To: 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>, 
 Mario Limonciello <mario.limonciello@....com>
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, Kurt Borja <kuurtb@...il.com>
Subject: [PATCH v2 1/5] platform/x86: firmware_attributes_class: Add device
 initialization methods

From: Thomas Weißschuh <linux@...ssschuh.net>

Currently each user of firmware_attributes_class has to manually set up
kobjects, devices, etc.

Provide this infrastructure out-of-the-box through the newly introduced
fwat_device_register().

Reviewed-by: Mario Limonciello <mario.limonciello@....com>
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
Co-developed-by: Kurt Borja <kuurtb@...il.com>
Signed-off-by: Kurt Borja <kuurtb@...il.com>
---
 drivers/platform/x86/firmware_attributes_class.c | 166 +++++++++++++++++++++++
 drivers/platform/x86/firmware_attributes_class.h |  44 ++++++
 2 files changed, 210 insertions(+)

diff --git a/drivers/platform/x86/firmware_attributes_class.c b/drivers/platform/x86/firmware_attributes_class.c
index 736e96c186d9dc6d945517f090e9af903e93bbf4..e2dcf2781513b5b033b019780d3e28115e83a1a5 100644
--- a/drivers/platform/x86/firmware_attributes_class.c
+++ b/drivers/platform/x86/firmware_attributes_class.c
@@ -2,7 +2,13 @@
 
 /* Firmware attributes class helper module */
 
+#include <linux/device.h>
+#include <linux/device/class.h>
+#include <linux/kdev_t.h>
+#include <linux/kobject.h>
 #include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
 #include "firmware_attributes_class.h"
 
 const struct class firmware_attributes_class = {
@@ -10,6 +16,164 @@ const struct class firmware_attributes_class = {
 };
 EXPORT_SYMBOL_GPL(firmware_attributes_class);
 
+static ssize_t fwat_attrs_kobj_show(struct kobject *kobj, struct attribute *attr,
+				    char *buf)
+{
+	const struct fwat_attribute *fattr = to_fwat_attribute(attr);
+	struct fwat_device *fadev = to_fwat_device(kobj);
+
+	if (!fattr->show)
+		return -ENOENT;
+
+	return fattr->show(fadev->dev, fattr, buf);
+}
+
+static ssize_t fwat_attrs_kobj_store(struct kobject *kobj, struct attribute *attr,
+				     const char *buf, size_t count)
+{
+	const struct fwat_attribute *fattr = to_fwat_attribute(attr);
+	struct fwat_device *fadev = to_fwat_device(kobj);
+
+	if (!fattr->store)
+		return -ENOENT;
+
+	return fattr->store(fadev->dev, fattr, buf, count);
+}
+
+static const struct sysfs_ops fwat_attrs_kobj_ops = {
+	.show	= fwat_attrs_kobj_show,
+	.store	= fwat_attrs_kobj_store,
+};
+
+static void fwat_attrs_kobj_release(struct kobject *kobj)
+{
+	struct fwat_device *fadev = to_fwat_device(kobj);
+
+	kfree(fadev);
+}
+
+static const struct kobj_type fwat_attrs_ktype = {
+	.sysfs_ops	= &fwat_attrs_kobj_ops,
+	.release	= fwat_attrs_kobj_release,
+};
+
+/**
+ * fwat_device_register - Create and register a firmware-attributes class
+ *			  device
+ * @parent: Parent device
+ * @name: Name of the class device
+ * @data: Drvdata of the class device
+ * @groups: Sysfs groups for the custom `fwat_attrs_ktype` kobj_type
+ *
+ * NOTE: @groups are attached to the .attrs_kobj of the new fwat_device which
+ * has a custom ktype, which makes use of `struct fwat_attribute` to embed
+ * attributes.
+ *
+ * Return: pointer to the new fwat_device on success, ERR_PTR on failure
+ */
+struct fwat_device *
+fwat_device_register(struct device *parent, const char *name, void *data,
+		     const struct attribute_group **groups)
+{
+	struct fwat_device *fadev;
+	struct device *dev;
+	int ret;
+
+	if (!parent || !name)
+		return ERR_PTR(-EINVAL);
+
+	fadev = kzalloc(sizeof(*fadev), GFP_KERNEL);
+	if (!fadev)
+		return ERR_PTR(-ENOMEM);
+
+	dev = device_create(&firmware_attributes_class, parent, MKDEV(0, 0),
+			    data, "%s", name);
+	if (IS_ERR(dev)) {
+		kfree(fadev);
+		return ERR_CAST(dev);
+	}
+
+	ret = kobject_init_and_add(&fadev->attrs_kobj, &fwat_attrs_ktype, &dev->kobj,
+				   "attributes");
+	if (ret)
+		goto out_kobj_put;
+
+	if (groups) {
+		ret = sysfs_create_groups(&fadev->attrs_kobj, groups);
+		if (ret)
+			goto out_kobj_unregister;
+	}
+
+	fadev->dev = dev;
+	fadev->groups = groups;
+
+	kobject_uevent(&fadev->attrs_kobj, KOBJ_ADD);
+
+	return fadev;
+
+out_kobj_unregister:
+	kobject_del(&fadev->attrs_kobj);
+
+out_kobj_put:
+	kobject_put(&fadev->attrs_kobj);
+	device_unregister(dev);
+
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(fwat_device_register);
+
+void fwat_device_unregister(struct fwat_device *fwadev)
+{
+	if (fwadev->groups)
+		sysfs_remove_groups(&fwadev->attrs_kobj, fwadev->groups);
+	kobject_del(&fwadev->attrs_kobj);
+	kobject_put(&fwadev->attrs_kobj);
+	device_unregister(fwadev->dev);
+}
+EXPORT_SYMBOL_GPL(fwat_device_unregister);
+
+static void devm_fwat_device_release(void *data)
+{
+	struct fwat_device *fadev = data;
+
+	fwat_device_unregister(fadev);
+}
+
+/**
+ * devm_fwat_device_register - Create and register a firmware-attributes class
+ *			       device
+ * @parent: Parent device
+ * @name: Name of the class device
+ * @data: Drvdata of the class device
+ * @groups: Sysfs groups for the custom `fwat_attrs_ktype` kobj_type
+ *
+ * Device managed version of fwat_device_register().
+ *
+ * NOTE: @groups are attached to the .attrs_kobj of the new fwat_device which
+ * has a custom ktype, which makes use of `struct fwat_attribute` to embed
+ * attributes.
+ *
+ * Return: pointer to the new fwat_device on success, ERR_PTR on failure
+ */
+struct fwat_device *
+devm_fwat_device_register(struct device *parent, const char *name, void *data,
+			  const struct attribute_group **groups)
+{
+	struct fwat_device *fadev;
+	int ret;
+
+	fadev = fwat_device_register(parent, name, data, groups);
+	if (IS_ERR(fadev))
+		return fadev;
+
+	ret = devm_add_action_or_reset(parent, devm_fwat_device_release, fadev);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return fadev;
+}
+EXPORT_SYMBOL_GPL(devm_fwat_device_register);
+
 static __init int fw_attributes_class_init(void)
 {
 	return class_register(&firmware_attributes_class);
@@ -23,5 +187,7 @@ static __exit void fw_attributes_class_exit(void)
 module_exit(fw_attributes_class_exit);
 
 MODULE_AUTHOR("Mark Pearson <markpearson@...ovo.com>");
+MODULE_AUTHOR("Thomas Weißschuh <linux@...ssschuh.net>");
+MODULE_AUTHOR("Kurt Borja <kuurtb@...il.com>");
 MODULE_DESCRIPTION("Firmware attributes class helper module");
 MODULE_LICENSE("GPL");
diff --git a/drivers/platform/x86/firmware_attributes_class.h b/drivers/platform/x86/firmware_attributes_class.h
index d27abe54fcf9812a2f0868eec5426bbc8e7eb21c..ad94bf91e5af30a2b8feb9abf224ee6f0d17600a 100644
--- a/drivers/platform/x86/firmware_attributes_class.h
+++ b/drivers/platform/x86/firmware_attributes_class.h
@@ -5,8 +5,52 @@
 #ifndef FW_ATTR_CLASS_H
 #define FW_ATTR_CLASS_H
 
+#include <linux/container_of.h>
+#include <linux/device.h>
 #include <linux/device/class.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
 
 extern const struct class firmware_attributes_class;
 
+/**
+ * struct fwat_device - The firmware-attributes device
+ * @dev: The class device.
+ * @attrs_kobj: The "attributes" root kobject.
+ * @groups: Sysfs groups attached to the @attrs_kobj.
+ */
+struct fwat_device {
+	struct device *dev;
+	struct kobject attrs_kobj;
+	const struct attribute_group **groups;
+};
+
+#define to_fwat_device(_k)	container_of_const(_k, struct fwat_device, attrs_kobj)
+
+/**
+ * struct fwat_attribute - The firmware-attributes's custom attribute
+ * @attr: Embedded struct attribute.
+ * @show: Show method called by the "attributes" kobject's ktype.
+ * @store: Store method called by the "attributes" kobject's ktype.
+ */
+struct fwat_attribute {
+	struct attribute attr;
+	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);
+};
+
+#define to_fwat_attribute(_a) container_of_const(_a, struct fwat_attribute, attr)
+
+struct fwat_device * __must_check
+fwat_device_register(struct device *parent, const char *name, void *data,
+		     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 attribute_group **groups);
+
 #endif /* FW_ATTR_CLASS_H */

-- 
2.49.0

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