linux-kernel - [PATCH 5/6] samples/kobject: add is_visible() callback to attribute group

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Message-Id: <20250116-sysfs-const-attr-prep-v1-5-15e72dba4205@weissschuh.net>
Date: Thu, 16 Jan 2025 18:32:31 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 5/6] samples/kobject: add is_visible() callback to
 attribute group

There was no example for the is_visible() callback so far.

It will also become an example and test for the constification of
'struct attribute' later.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 samples/kobject/kset-example.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/samples/kobject/kset-example.c b/samples/kobject/kset-example.c
index 552d7e363539a8f82ab8e0446c732f85ed2c5612..7d8c68763ff8af696cbafaed1d5f1b173bb4860e 100644
--- a/samples/kobject/kset-example.c
+++ b/samples/kobject/kset-example.c
@@ -178,7 +178,22 @@ static struct attribute *foo_default_attrs[] = {
 	&bar_attribute.attr,
 	NULL,	/* need to NULL terminate the list of attributes */
 };
-ATTRIBUTE_GROUPS(foo_default);
+
+static umode_t foo_default_attrs_is_visible(struct kobject *kobj,
+					    struct attribute *attr,
+					    int n)
+{
+	/* Hide attributes with the same name as the kobject. */
+	if (strcmp(kobject_name(kobj), attr->name) == 0)
+		return 0;
+	return attr->mode;
+}
+
+static const struct attribute_group foo_default_group = {
+	.attrs		= foo_default_attrs,
+	.is_visible	= foo_default_attrs_is_visible,
+};
+__ATTRIBUTE_GROUPS(foo_default);

 /*
  * Our own ktype for our kobjects.  Here we specify our sysfs ops, the

-- 
2.48.1