example/mi-conf: Add an example for MI transport configuration

With the Read MI Data Structure and MI Configuration Set functions
available, we can query a device for its maximum MTU, and update the
current MTU to suit.

This also requires telling the local MCTP stack about the new MTU too,
by sending a d-bus message to `mctpd`.

This change adds a little example for this functionality, where we
perform the MI query and configuration, and implements the d-bus
communication for the local stack control.

Signed-off-by: Jeremy Kerr <[email protected]>

Author: jk-ozlabs

examples/meson.build

@@ -39,3 +39,12 @@ executable(
     dependencies: libnvme_mi_dep,
     include_directories: [incdir, internal_incdir]
 )
+
+if libsystemd_dep.found()
+    executable(
+        'mi-conf',
+        ['mi-conf.c'],
+        dependencies: [libnvme_mi_dep, libsystemd_dep],
+        include_directories: [incdir, internal_incdir]
+    )
+endif

examples/mi-conf.c

@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+/**
+ * This file is part of libnvme.
+ * Copyright (c) 2022 Code Construct Pty Ltd.
+ *
+ * Authors: Jeremy Kerr <[email protected]>
+ */
+
+/**
+ * mi-conf: query a device for optimal MTU and set for both the local MCTP
+ * route (through dbus to mctpd) and the device itself (through NVMe-MI
+ * configuration commands)
+ */
+
+#include <err.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <libnvme-mi.h>
+
+#include <ccan/array_size/array_size.h>
+#include <ccan/endian/endian.h>
+
+#include <systemd/sd-bus.h>
+
+#define MCTP_DBUS_NAME "xyz.openbmc_project.MCTP"
+#define MCTP_DBUS_PATH "/xyz/openbmc_project/mctp"
+#define MCTP_DBUS_EP_IFACE "au.com.CodeConstruct.MCTP.Endpoint"
+
+static int parse_mctp(const char *devstr, unsigned int *net, uint8_t *eid)
+{
+	int rc;
+
+	rc = sscanf(devstr, "mctp:%u,%hhu", net, eid);
+	if (rc != 2)
+		return -1;
+
+	return 0;
+}
+
+int find_port(nvme_mi_ep_t ep, uint8_t *portp, uint16_t *mtup)
+{
+	struct nvme_mi_read_nvm_ss_info ss_info;
+	struct nvme_mi_read_port_info port_info;
+	uint8_t port;
+	bool found;
+	int rc;
+
+	/* query number of ports */
+	rc = nvme_mi_mi_read_mi_data_subsys(ep, &ss_info);
+	if (rc) {
+		warn("Failed reading subsystem info");
+		return -1;
+	}
+
+	found = false;
+	for (port = 0; port <= ss_info.nump; port++) {
+		rc = nvme_mi_mi_read_mi_data_port(ep, port, &port_info);
+		if (rc) {
+			warn("Failed reading port info for port %ud", port);
+			return -1;
+		}
+
+		/* skip non-SMBus ports */
+		if (port_info.portt != 0x2)
+			continue;
+
+		if (found) {
+			warn("Mutliple SMBus ports; skipping duplicate");
+		} else {
+			*portp = port;
+			*mtup = port_info.mmctptus;
+			found = true;
+		}
+	}
+
+	return found ? 0 : 1;
+}
+
+int set_local_mtu(sd_bus *bus, unsigned int net, uint8_t eid, uint32_t mtu)
+{
+	sd_bus_message *resp;
+	sd_bus_error err;
+	char *ep_path;
+	int rc;
+
+	rc = asprintf(&ep_path, "%s/%u/%hhu", MCTP_DBUS_PATH, net, eid);
+	if (rc < 0) {
+		warn("Failed to create dbus path");
+		return -1;
+	}
+
+	rc = sd_bus_call_method(bus, MCTP_DBUS_NAME, ep_path,
+				MCTP_DBUS_EP_IFACE, "SetMTU", &err, &resp,
+				"u", mtu);
+	if (rc < 0) {
+		warnx("Failed to set local MTU: %s", strerror(-rc));
+		return -1;
+	}
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	uint16_t cur_mtu, mtu;
+	const char *devstr;
+	uint8_t eid, port;
+	nvme_root_t root;
+	unsigned int net;
+	nvme_mi_ep_t ep;
+	sd_bus *bus;
+	int rc;
+
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s mctp:<net>,<eid>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	devstr = argv[1];
+	rc = parse_mctp(devstr, &net, &eid);
+	if (rc)
+		errx(EXIT_FAILURE, "can't parse MI device string '%s'", devstr);
+
+	root = nvme_mi_create_root(stderr, DEFAULT_LOGLEVEL);
+	if (!root)
+		err(EXIT_FAILURE, "can't create NVMe root");
+
+	ep = nvme_mi_open_mctp(root, net, eid);
+	if (!ep) {
+		warnx("can't open MCTP endpoint %d:%d", net, eid);
+		goto out_free_root;
+	}
+
+	rc = sd_bus_default_system(&bus);
+	if (rc < 0) {
+		goto out_close_ep;
+		warnx("Failed opening D-Bus: %s\n", strerror(-rc));
+	}
+
+	rc = find_port(ep, &port, &mtu);
+	if (rc) {
+		warnx("Can't find SMBus port information");
+		goto out_close_bus;
+	}
+
+	rc = nvme_mi_mi_config_get_mctp_mtu(ep, port, &cur_mtu);
+	if (rc) {
+		cur_mtu = 0;
+		warn("Can't query current MTU; no way to revert on failure");
+	}
+
+	if (mtu == cur_mtu) {
+		printf("Current MTU (%d) is already at max\n", cur_mtu);
+		goto out_close_bus;
+	}
+
+	rc = nvme_mi_mi_config_set_mctp_mtu(ep, port, mtu);
+	if (rc) {
+		warn("Can't set MCTP MTU");
+		goto out_close_bus;
+	}
+
+	rc = set_local_mtu(bus, net, eid, mtu);
+	if (rc) {
+		/* revert if we have an old setting */
+		if (cur_mtu) {
+			rc = nvme_mi_mi_config_set_mctp_mtu(ep, port, cur_mtu);
+			if (rc)
+				warn("Failed to restore previous MTU!");
+			rc = -1;
+		}
+	} else {
+		printf("MTU for port %u set to %d (was %d)\n",
+		       port, mtu, cur_mtu);
+	}
+
+out_close_bus:
+	sd_bus_close(bus);
+out_close_ep:
+	nvme_mi_close(ep);
+out_free_root:
+	nvme_mi_free_root(root);
+
+	return rc ? EXIT_FAILURE : EXIT_SUCCESS;
+}
+