[RFC net-next 06/17] net/dibs: Create net/dibs

[Alexandra Winter <wintera@linux.ibm.com>]

Create an 'DIBS' shim layer that will provide generic functionality and
declarations for dibs device drivers and dibs clients.

Following patches will add functionality.

Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
---
 MAINTAINERS          |  7 +++++++
 include/linux/dibs.h | 42 ++++++++++++++++++++++++++++++++++++++++++
 net/Kconfig          |  1 +
 net/Makefile         |  1 +
 net/dibs/Kconfig     | 14 ++++++++++++++
 net/dibs/Makefile    |  7 +++++++
 net/dibs/dibs_main.c | 39 +++++++++++++++++++++++++++++++++++++++
 7 files changed, 111 insertions(+)
 create mode 100644 include/linux/dibs.h
 create mode 100644 net/dibs/Kconfig
 create mode 100644 net/dibs/Makefile
 create mode 100644 net/dibs/dibs_main.c

diff --git a/MAINTAINERS b/MAINTAINERS
index b968bc6959d1..e28d92f64236 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12948,6 +12948,13 @@ F:	Documentation/devicetree/bindings/hwmon/renesas,isl28022.yaml
 F:	Documentation/hwmon/isl28022.rst
 F:	drivers/hwmon/isl28022.c
 
+DIBS (DIRECT INTERNAL BUFFER SHARING)
+M:	Alexandra Winter <wintera@linux.ibm.com>
+L:	netdev@vger.kernel.org
+S:	Supported
+F:	include/linux/dibs.h
+F:	net/dibs/
+
 ISOFS FILESYSTEM
 M:	Jan Kara <jack@suse.cz>
 L:	linux-fsdevel@vger.kernel.org
diff --git a/include/linux/dibs.h b/include/linux/dibs.h
new file mode 100644
index 000000000000..3f4175aaa732
--- /dev/null
+++ b/include/linux/dibs.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Direct Internal Buffer Sharing
+ *
+ *  Definitions for the DIBS module
+ *
+ *  Copyright IBM Corp. 2025
+ */
+#ifndef _DIBS_H
+#define _DIBS_H
+
+/* DIBS - Direct Internal Buffer Sharing - concept
+ * -----------------------------------------------
+ * In the case of multiple system sharing the same hardware, dibs fabrics can
+ * provide dibs devices to these systems. The systems use dibs devices of the
+ * same fabric to communicate via dmbs (Direct Memory Buffers). Each dmb has
+ * exactly one owning local dibs device and one remote using dibs device, that
+ * is authorized to write into this dmb. This access control is provided by the
+ * dibs fabric.
+ *
+ * Because the access to the dmb is based on access to physical memory, it is
+ * lossless and synchronous. The remote devices can directly access any offset
+ * of the dmb.
+ *
+ * Dibs fabrics, dibs devices and dmbs are identified by tokens and ids.
+ * Dibs fabric id is unique within the same hardware (with the exception of the
+ * dibs loopback fabric), dmb token is unique within the same fabric, dibs
+ * device gids are guaranteed to be unique within the same fabric and
+ * statistically likely to be globally unique. The exchange of these tokens and
+ * ids between the systems is not part of the dibs concept.
+ *
+ * The dibs layer provides an abstraction between dibs device drivers and dibs
+ * clients.
+ */
+
+#define MAX_DIBS_CLIENTS	8
+
+struct dibs_client {
+	const char *name;
+};
+
+#endif	/* _DIBS_H */
diff --git a/net/Kconfig b/net/Kconfig
index d5865cf19799..5410226f314b 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -87,6 +87,7 @@ source "net/tls/Kconfig"
 source "net/xfrm/Kconfig"
 source "net/iucv/Kconfig"
 source "net/smc/Kconfig"
+source "net/dibs/Kconfig"
 source "net/xdp/Kconfig"
 
 config NET_HANDSHAKE
diff --git a/net/Makefile b/net/Makefile
index aac960c41db6..3e4771cfe48e 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_TIPC)		+= tipc/
 obj-$(CONFIG_NETLABEL)		+= netlabel/
 obj-$(CONFIG_IUCV)		+= iucv/
 obj-$(CONFIG_SMC)		+= smc/
+obj-$(CONFIG_DIBS)		+= dibs/
 obj-$(CONFIG_RFKILL)		+= rfkill/
 obj-$(CONFIG_NET_9P)		+= 9p/
 obj-$(CONFIG_CAIF)		+= caif/
diff --git a/net/dibs/Kconfig b/net/dibs/Kconfig
new file mode 100644
index 000000000000..968c52938708
--- /dev/null
+++ b/net/dibs/Kconfig
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0
+config DIBS
+	tristate "DIBS support"
+	default n
+	help
+	  Direct Internal Buffer Sharing (DIBS)
+	  A communication method that uses common physical (internal) memory
+	  for synchronous direct access into a remote buffer.
+
+	  Select this option to provide the abstraction layer between
+	  dibs devices and dibs clients like the SMC protocol.
+
+	  To compile as a module choose M. The module name is dibs.
+	  If unsure, choose N.
diff --git a/net/dibs/Makefile b/net/dibs/Makefile
new file mode 100644
index 000000000000..825dec431bfc
--- /dev/null
+++ b/net/dibs/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# DIBS class module
+#
+
+dibs-y += dibs_main.o
+obj-$(CONFIG_DIBS) += dibs.o
diff --git a/net/dibs/dibs_main.c b/net/dibs/dibs_main.c
new file mode 100644
index 000000000000..348242fd05dd
--- /dev/null
+++ b/net/dibs/dibs_main.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  DIBS - Direct Internal Buffer Sharing
+ *
+ *  Implementation of the DIBS class module
+ *
+ *  Copyright IBM Corp. 2025
+ */
+#define KMSG_COMPONENT "dibs"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/err.h>
+#include <linux/dibs.h>
+
+MODULE_DESCRIPTION("Direct Internal Buffer Sharing class");
+MODULE_LICENSE("GPL");
+
+/* use an array rather a list for fast mapping: */
+static struct dibs_client *clients[MAX_DIBS_CLIENTS];
+static u8 max_client;
+
+static int __init dibs_init(void)
+{
+	memset(clients, 0, sizeof(clients));
+	max_client = 0;
+
+	pr_info("module loaded\n");
+	return 0;
+}
+
+static void __exit dibs_exit(void)
+{
+	pr_info("module unloaded\n");
+}
+
+module_init(dibs_init);
+module_exit(dibs_exit);
-- 
2.48.1