On Sun, 2021-11-28 at 15:55 +0300, Sergey Ryazanov wrote:

+#ifdef CONFIG_WWAN_DEBUGFS
 struct dentry *wwan_get_debugfs_dir(struct device *parent);
+#else
+static inline struct dentry *wwan_get_debugfs_dir(struct device *parent)
+{
+	return NULL;
+}
+#endif

Now I have to send another email anyway ... but this one probably should
be ERR_PTR(-ENODEV) or something, a la debugfs_create_dir() if debugfs
is disabled, because then a trivial user of wwan's debugfs doesn't even
have to care about whether it's enabled or not, it can just
debugfs_create_dir() for its own and the debugfs core code will check
and return immediately. Yes that's a bit more code space, but if you
just have a debugfs file or two, having an extra Kconfig option is
possibly overkill too. Especially if we get into this path because
DEBUG_FS is disabled *entirely*, and thus all the functions will be
empty inlines (but it might not be, so it should be consistent with
debugfs always returning non-NULL).

johannes