dibs: Create drivers/dibs

Create the file structure for a 'DIBS - Direct Internal Buffer Sharing'
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>
Link: https://patch.msgid.link/20250918110500.1731261-4-wintera@linux.ibm.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

MAINTAINERS

@@ -7132,6 +7132,13 @@ L:	linux-gpio@vger.kernel.org
 S:	Maintained
 F:	drivers/gpio/gpio-gpio-mm.c
 
+DIBS (DIRECT INTERNAL BUFFER SHARING)
+M:	Alexandra Winter <wintera@linux.ibm.com>
+L:	netdev@vger.kernel.org
+S:	Supported
+F:	drivers/dibs/
+F:	include/linux/dibs.h
+
 DIGITEQ AUTOMOTIVE MGB4 V4L2 DRIVER
 M:	Martin Tuma <martin.tuma@digiteqautomotive.com>
 L:	linux-media@vger.kernel.org

drivers/Makefile

@@ -195,4 +195,5 @@ obj-$(CONFIG_DRM_ACCEL)		+= accel/
 obj-$(CONFIG_CDX_BUS)		+= cdx/
 obj-$(CONFIG_DPLL)		+= dpll/
 
+obj-$(CONFIG_DIBS)		+= dibs/
 obj-$(CONFIG_S390)		+= s390/

drivers/dibs/Kconfig

@@ -0,0 +1,12 @@
+# 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.
+	  The module name is dibs.

drivers/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

drivers/dibs/dibs_main.c

@@ -0,0 +1,37 @@
+// 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;
+
+	return 0;
+}
+
+static void __exit dibs_exit(void)
+{
+}
+
+module_init(dibs_init);
+module_exit(dibs_exit);

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 */

net/Kconfig

@@ -88,6 +88,7 @@ source "net/tls/Kconfig"
 source "net/xfrm/Kconfig"
 source "net/iucv/Kconfig"
 source "net/smc/Kconfig"
+source "drivers/dibs/Kconfig"
 source "net/xdp/Kconfig"
 
 config NET_HANDSHAKE