sysfs: Introduce DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE()

One of the first users of DEFINE_SYSFS_GROUP_VISIBLE() did this:

	static umode_t dp0_attr_visible(struct kobject *kobj,
					struct attribute *attr,
					int n)
	{
		struct sdw_slave *slave = dev_to_sdw_dev(kobj_to_dev(kobj));

		if (slave->prop.dp0_prop)
			return attr->mode;
		return 0;
	}

	static bool dp0_group_visible(struct kobject *kobj)
	{
		struct sdw_slave *slave = dev_to_sdw_dev(kobj_to_dev(kobj));

		if (slave->prop.dp0_prop)
			return true;
		return false;
	}
	DEFINE_SYSFS_GROUP_VISIBLE(dp0);

...i.e. the _group_visible() helper is identical to the _attr_visible()
helper. Use the "simple" helper to reduce that to:

	static bool dp0_group_visible(struct kobject *kobj)
	{
		struct sdw_slave *slave = dev_to_sdw_dev(kobj_to_dev(kobj));

		if (slave->prop.dp0_prop)
			return true;
		return false;
	}
	DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE(dp0);

Remove the need to specify per attribute visibility if the goal is to
hide the entire group.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/170863446625.1479840.10593839479268727913.stgit@dwillia2-xfh.jf.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/sysfs.h

@@ -140,7 +140,9 @@ struct attribute_group {
  * };
  *
  * Note that it expects <name>_attr_visible and <name>_group_visible to
- * be defined.
+ * be defined. For cases where individual attributes do not need
+ * separate visibility consideration, only entire group visibility at
+ * once, see DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE().
  */
 #define DEFINE_SYSFS_GROUP_VISIBLE(name)                             \
 	static inline umode_t sysfs_group_visible_##name(            \
@@ -151,6 +153,38 @@ struct attribute_group {
 		return name##_attr_visible(kobj, attr, n);           \
 	}
 
+/*
+ * DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE(name):
+ *	A helper macro to pair with SYSFS_GROUP_VISIBLE() that like
+ *	DEFINE_SYSFS_GROUP_VISIBLE() controls group visibility, but does
+ *	not require the implementation of a per-attribute visibility
+ *	callback.
+ * Ex.
+ *
+ * static bool example_group_visible(struct kobject *kobj)
+ * {
+ *       if (example_group_condition)
+ *               return false;
+ *       return true;
+ * }
+ *
+ * DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE(example);
+ *
+ * static struct attribute_group example_group = {
+ *       .name = "example",
+ *       .is_visible = SYSFS_GROUP_VISIBLE(example),
+ *       .attrs = &example_attrs,
+ * };
+ */
+#define DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE(name)                   \
+	static inline umode_t sysfs_group_visible_##name(         \
+		struct kobject *kobj, struct attribute *a, int n) \
+	{                                                         \
+		if (n == 0 && !name##_group_visible(kobj))        \
+			return SYSFS_GROUP_INVISIBLE;             \
+		return a->mode;                                   \
+	}
+
 /*
  * Same as DEFINE_SYSFS_GROUP_VISIBLE, but for groups with only binary
  * attributes. If an attribute_group defines both text and binary
@@ -166,6 +200,15 @@ struct attribute_group {
 		return name##_attr_visible(kobj, attr, n);               \
 	}
 
+#define DEFINE_SIMPLE_SYSFS_BIN_GROUP_VISIBLE(name)                   \
+	static inline umode_t sysfs_group_visible_##name(             \
+		struct kobject *kobj, struct bin_attribute *a, int n) \
+	{                                                             \
+		if (n == 0 && !name##_group_visible(kobj))            \
+			return SYSFS_GROUP_INVISIBLE;                 \
+		return a->mode;                                       \
+	}
+
 #define SYSFS_GROUP_VISIBLE(fn) sysfs_group_visible_##fn
 
 /*