linux-kernel - [PATCH] rfkill: allocate static minor

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Date:   Thu, 24 Oct 2019 19:40:42 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     arnd@...db.de, gregkh@...uxfoundation.org,
        johannes@...solutions.net, davem@...emloft.net
Cc:     linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH] rfkill: allocate static minor

udev has a feature of creating /dev/<node> device-nodes if it finds
a devnode:<node> modalias. This allows for auto-loading of modules that
provide the node. This requires to use a statically allocated minor
number for misc character devices.

However, rfkill uses dynamic minor numbers and prevents auto-loading
of the module. So allocate the next static misc minor number and use
it for rfkill.

Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
---
 include/linux/miscdevice.h | 1 +
 net/rfkill/core.c          | 9 +++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
index 3247a3dc7934..b06b75776a32 100644
--- a/include/linux/miscdevice.h
+++ b/include/linux/miscdevice.h
@@ -57,6 +57,7 @@
 #define UHID_MINOR		239
 #define USERIO_MINOR		240
 #define VHOST_VSOCK_MINOR	241
+#define RFKILL_MINOR		242
 #define MISC_DYNAMIC_MINOR	255
 
 struct device;
diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index f9b08a6d8dbe..0bf9bf1ceb8f 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -1316,10 +1316,12 @@ static const struct file_operations rfkill_fops = {
 	.llseek		= no_llseek,
 };
 
+#define RFKILL_NAME "rfkill"
+
 static struct miscdevice rfkill_miscdev = {
-	.name	= "rfkill",
 	.fops	= &rfkill_fops,
-	.minor	= MISC_DYNAMIC_MINOR,
+	.name	= RFKILL_NAME,
+	.minor	= RFKILL_MINOR,
 };
 
 static int __init rfkill_init(void)
@@ -1371,3 +1373,6 @@ static void __exit rfkill_exit(void)
 	class_unregister(&rfkill_class);
 }
 module_exit(rfkill_exit);
+
+MODULE_ALIAS_MISCDEV(RFKILL_MINOR);
+MODULE_ALIAS("devname:" RFKILL_NAME);
-- 
2.21.0