s390/net: add pnetid support

s390 hardware supports the definition of a so-call Physical NETwork
IDentifier (short PNETID) per network device port. These PNETIDS
can be used to identify network devices that are attached to the same
physical network (broadcast domain).

This patch provides the interface to extract the PNETID of a port of
a device attached to the ccw-bus or pci-bus.

Parts of this patch are based on an initial implementation by
Thomas Richter.
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -847,6 +847,10 @@ config CCW
 
 source "drivers/Kconfig"
 
+config HAVE_PNETID
+	tristate
+	default (SMC || CCWGROUP)
+
 source "fs/Kconfig"
 
 source "arch/s390/Kconfig.debug"

arch/s390/include/asm/pnet.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  IBM System z PNET ID Support
+ *
+ *    Copyright IBM Corp. 2018
+ */
+
+#ifndef _ASM_S390_PNET_H
+#define _ASM_S390_PNET_H
+
+#include <linux/device.h>
+#include <linux/types.h>
+
+#define PNETIDS_LEN		64	/* Total utility string length in bytes
+					 * to cover up to 4 PNETIDs of 16 bytes
+					 * for up to 4 device ports
+					 */
+#define MAX_PNETID_LEN		16	/* Max.length of a single port PNETID */
+#define MAX_PNETID_PORTS	(PNETIDS_LEN / MAX_PNETID_LEN)
+					/* Max. # of ports with a PNETID */
+
+int pnet_id_by_dev_port(struct device *dev, unsigned short port, u8 *pnetid);
+#endif /* _ASM_S390_PNET_H */

arch/s390/net/Makefile

@@ -3,3 +3,4 @@
 # Arch-specific network modules
 #
 obj-$(CONFIG_BPF_JIT) += bpf_jit.o bpf_jit_comp.o
+obj-$(CONFIG_HAVE_PNETID) += pnet.o

arch/s390/net/pnet.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  IBM System z PNET ID Support
+ *
+ *    Copyright IBM Corp. 2018
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/types.h>
+#include <asm/ccwgroup.h>
+#include <asm/ccwdev.h>
+#include <asm/pnet.h>
+
+/*
+ * Get the PNETIDs from a device.
+ * s390 hardware supports the definition of a so-called Physical Network
+ * Identifier (short PNETID) per network device port. These PNETIDs can be
+ * used to identify network devices that are attached to the same physical
+ * network (broadcast domain).
+ *
+ * The device can be
+ * - a ccwgroup device with all bundled subchannels having the same PNETID
+ * - a PCI attached network device
+ *
+ * Returns:
+ * 0:		PNETIDs extracted from device.
+ * -ENOMEM:	No memory to extract utility string.
+ * -EOPNOTSUPP: Device type without utility string support
+ */
+static int pnet_ids_by_device(struct device *dev, u8 *pnetids)
+{
+	memset(pnetids, 0, PNETIDS_LEN);
+	if (dev_is_ccwgroup(dev)) {
+		struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
+		u8 *util_str;
+
+		util_str = ccw_device_get_util_str(gdev->cdev[0], 0);
+		if (!util_str)
+			return -ENOMEM;
+		memcpy(pnetids, util_str, PNETIDS_LEN);
+		kfree(util_str);
+		return 0;
+	}
+	if (dev_is_pci(dev)) {
+		struct zpci_dev *zdev = to_zpci(to_pci_dev(dev));
+
+		memcpy(pnetids, zdev->util_str, sizeof(zdev->util_str));
+		return 0;
+	}
+	return -EOPNOTSUPP;
+}
+
+/*
+ * Extract the pnetid for a device port.
+ *
+ * Return 0 if a pnetid is found and -ENOENT otherwise.
+ */
+int pnet_id_by_dev_port(struct device *dev, unsigned short port, u8 *pnetid)
+{
+	u8 pnetids[MAX_PNETID_PORTS][MAX_PNETID_LEN];
+	static const u8 zero[MAX_PNETID_LEN] = { 0 };
+	int rc = 0;
+
+	if (!dev || port >= MAX_PNETID_PORTS)
+		return -ENOENT;
+
+	if (!pnet_ids_by_device(dev, (u8 *)pnetids) &&
+	    memcmp(pnetids[port], zero, MAX_PNETID_LEN))
+		memcpy(pnetid, pnetids[port], MAX_PNETID_LEN);
+	else
+		rc = -ENOENT;
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(pnet_id_by_dev_port);
+
+MODULE_DESCRIPTION("pnetid determination from utility strings");
+MODULE_LICENSE("GPL");