smb: smbdirect: introduce the basic smbdirect.ko

This exports the functions needed by cifs.ko and ksmbd.ko.

It doesn't yet provide a generic socket layer, but it
is a good start to introduce that on top.
It will be much easier after Davids refactoring
using MSG_SPLICE_PAGES, will make it easier to
use the socket layer without an additional copy.

Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/Kconfig

@@ -4,6 +4,7 @@
 
 source "fs/smb/client/Kconfig"
 source "fs/smb/server/Kconfig"
+source "fs/smb/common/smbdirect/Kconfig"
 
 config SMBFS
 	tristate

fs/smb/common/Makefile

@@ -4,3 +4,4 @@
 #
 
 obj-$(CONFIG_SMBFS) += cifs_md4.o
+obj-$(CONFIG_SMB_COMMON_SMBDIRECT) += smbdirect/

fs/smb/common/smbdirect/Kconfig

@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# smbdirect configuration
+
+config SMB_COMMON_SMBDIRECT
+	def_tristate n
+	depends on INFINIBAND && INFINIBAND_ADDR_TRANS
+	depends on m || INFINIBAND=y
+	select SG_POOL

fs/smb/common/smbdirect/Makefile

@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Makefile for smbdirect support
+#
+
+obj-$(CONFIG_SMB_COMMON_SMBDIRECT) += smbdirect.o
+
+smbdirect-y := \
+	smbdirect_socket.o	\
+	smbdirect_connection.o	\
+	smbdirect_mr.o		\
+	smbdirect_rw.o		\
+	smbdirect_debug.o	\
+	smbdirect_connect.o	\
+	smbdirect_listen.o	\
+	smbdirect_accept.o	\
+	smbdirect_main.o

fs/smb/common/smbdirect/smbdirect_internal.h

@@ -13,6 +13,15 @@
 #include "smbdirect.h"
 #include "smbdirect_pdu.h"
 #include "smbdirect_public.h"
+
+#include <linux/mutex.h>
+
+struct smbdirect_module_state {
+	struct mutex mutex;
+};
+
+extern struct smbdirect_module_state smbdirect_globals;
+
 #include "smbdirect_socket.h"
 
 #ifdef SMBDIRECT_USE_INLINE_C_FILES

fs/smb/common/smbdirect/smbdirect_main.c

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (c) 2025, Stefan Metzmacher
+ */
+
+#include "smbdirect_internal.h"
+#include <linux/module.h>
+
+struct smbdirect_module_state smbdirect_globals = {
+	.mutex = __MUTEX_INITIALIZER(smbdirect_globals.mutex),
+};
+
+static __init int smbdirect_module_init(void)
+{
+	pr_notice("subsystem loading...\n");
+	mutex_lock(&smbdirect_globals.mutex);
+
+	/* TODO... */
+
+	mutex_unlock(&smbdirect_globals.mutex);
+	pr_notice("subsystem loaded\n");
+	return 0;
+}
+
+static __exit void smbdirect_module_exit(void)
+{
+	pr_notice("subsystem unloading...\n");
+	mutex_lock(&smbdirect_globals.mutex);
+
+	/* TODO... */
+
+	mutex_unlock(&smbdirect_globals.mutex);
+	pr_notice("subsystem unloaded\n");
+}
+
+module_init(smbdirect_module_init);
+module_exit(smbdirect_module_exit);
+
+MODULE_DESCRIPTION("smbdirect subsystem");
+MODULE_LICENSE("GPL");