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@holtmann.org>
Link: https://lore.kernel.org/r/20191024174042.19851-1-marcel@holtmann.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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;

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);