linux-kernel - [PATCH v1 1/1] driver core: faux: Add sysfs groups after probing

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Message-ID: <20250225170318.3826-1-kuurtb@gmail.com>
Date: Tue, 25 Feb 2025 12:03:18 -0500
From: Kurt Borja <kuurtb@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Kurt Borja <kuurtb@...il.com>,
	linux-kernel@...r.kernel.org
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH v1 1/1] driver core: faux: Add sysfs groups after probing

Move sysfs group adding to the bus_type's probe. Specifically after the
user's probe callback succeeds. Removal is also done in the bus_type's
remove callback.

This approach approximates the order in which the driver core adds and
removes driver .dev_groups of a device to avoid lifetime issues, which
can't be used in this case because the faux_bus is a single driver bus.

This effectively lets consumers of this API initialize resources on the
.probe callback and then use them inside is_visible/show/store methods,
through faux_device_get_drvdata() without races.

Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Danilo Krummrich <dakr@...nel.org>
Signed-off-by: Kurt Borja <kuurtb@...il.com>
---
 drivers/base/faux.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/base/faux.c b/drivers/base/faux.c
index 407c1d1aad50..9054d346bd7f 100644
--- a/drivers/base/faux.c
+++ b/drivers/base/faux.c
@@ -25,6 +25,7 @@
 struct faux_object {
 	struct faux_device faux_dev;
 	const struct faux_device_ops *faux_ops;
+	const struct attribute_group **groups;
 };
 #define to_faux_object(dev) container_of_const(dev, struct faux_object, faux_dev.dev)
 
@@ -43,10 +44,21 @@ static int faux_probe(struct device *dev)
 	struct faux_object *faux_obj = to_faux_object(dev);
 	struct faux_device *faux_dev = &faux_obj->faux_dev;
 	const struct faux_device_ops *faux_ops = faux_obj->faux_ops;
-	int ret = 0;
+	int ret;
 
-	if (faux_ops && faux_ops->probe)
+	if (faux_ops && faux_ops->probe) {
 		ret = faux_ops->probe(faux_dev);
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * Add groups after the probe succeeds to ensure resources are
+	 * initialized correctly
+	 */
+	ret = device_add_groups(dev, faux_obj->groups);
+	if (ret && faux_ops && faux_ops->remove)
+		faux_ops->remove(faux_dev);
 
 	return ret;
 }
@@ -57,6 +69,8 @@ static void faux_remove(struct device *dev)
 	struct faux_device *faux_dev = &faux_obj->faux_dev;
 	const struct faux_device_ops *faux_ops = faux_obj->faux_ops;
 
+	device_remove_groups(dev, faux_obj->groups);
+
 	if (faux_ops && faux_ops->remove)
 		faux_ops->remove(faux_dev);
 }
@@ -124,8 +138,9 @@ struct faux_device *faux_device_create_with_groups(const char *name,
 	if (!faux_obj)
 		return NULL;
 
-	/* Save off the callbacks so we can use them in the future */
+	/* Save off the callbacks and groups so we can use them in the future */
 	faux_obj->faux_ops = faux_ops;
+	faux_obj->groups = groups;
 
 	/* Initialize the device portion and register it with the driver core */
 	faux_dev = &faux_obj->faux_dev;
@@ -138,7 +153,6 @@ struct faux_device *faux_device_create_with_groups(const char *name,
 	else
 		dev->parent = &faux_bus_root;
 	dev->bus = &faux_bus_type;
-	dev->groups = groups;
 	dev_set_name(dev, "%s", name);
 
 	ret = device_add(dev);

base-commit: c5e4c8c07a734bd9365876b1eecc3931d5a68101
-- 
2.48.1