feat: GNSS and DPLL emulation for hardware-free T-GM testing

.github/workflows/ci.yml

@@ -139,10 +139,16 @@ jobs:
           IFACE=$(ls /sys/bus/pci/devices/${DOMAIN}:${BUS}:02.0/net/ 2>/dev/null | head -1)
           [ -n "$IFACE" ] && ethtool -T "$IFACE" || echo "WARN: No interface found"
 
+      - name: DPLL unit tests
+        if: steps.load.outputs.load_ok == 'true'
+        run: sudo ./scripts/test-dpll.sh --no-load
+
       - name: Cleanup
         if: always()
         run: |
-          echo "1" | sudo tee /sys/bus/netdevsim/del_device 2>/dev/null || true
+          for id in $(ls /sys/bus/netdevsim/devices/ 2>/dev/null | sed 's/netdevsim//'); do
+            echo "$id" | sudo tee /sys/bus/netdevsim/del_device 2>/dev/null || true
+          done
           sudo rmmod netdevsim nsim_dpll nsim_ptp_mock nsim_ptp 2>/dev/null || true
           sudo dkms remove ${DKMS_PKG}/${DKMS_VER} --all 2>/dev/null || true
 

.gitignore

@@ -2,18 +2,24 @@
 *.o
 *.ko
 *.ko.cmd
+*.ko.zst
 *.mod
 *.mod.c
 *.mod.cmd
 *.order
 *.symvers
 *.unsigned
 *.o.d
+*.o.cmd
 .tmp_versions/
 .cache.mk
 modules.order
 Module.symvers
 
+# kbuild per-object command files
+.*.cmd
+.module-common.o
+
 # RPM build
 rpmbuild/
 *.tar.gz

99-nsim-ptp.rules

@@ -14,7 +14,15 @@
 # is not in the default cgroup device allowlist; containers and
 # systemd-sandboxed services (DevicePolicy=closed) would get
 # "Operation not permitted" without world-readable permissions.
+#
+# The bind-mount of /sys/class/nsim_ptp over /sys/class/ptp makes
+# PTP sysfs entries (pins, clock_name, etc.) visible at the standard
+# path expected by monitoring tools and the PTP dashboard.
 SUBSYSTEM=="nsim_ptp", KERNEL=="nsim_ptp[0-9]*", MODE="0666", \
-    RUN+="/bin/sh -c 'rm -f /dev/ptp%n; mknod /dev/ptp%n c %M %m; chmod 666 /dev/ptp%n'"
+    RUN+="/bin/sh -c 'rm -f /dev/ptp%n; mknod /dev/ptp%n c %M %m; chmod 666 /dev/ptp%n; if [ -d /sys/class/ptp ] && ! mountpoint -q /sys/class/ptp; then mount --bind /sys/class/nsim_ptp /sys/class/ptp 2>/dev/null || true; fi'"
 SUBSYSTEM=="nsim_ptp", KERNEL=="nsim_ptp[0-9]*", ACTION=="remove", \
     RUN+="/bin/rm -f /dev/ptp%n"
+
+# gpsd drops privileges to nobody; without world access it fails with
+# EACCES, frees the device, and ts2phc starves for NMEA.
+SUBSYSTEM=="gnss", KERNEL=="gnss[0-9]*", MODE="0666"

README.md

@@ -271,7 +271,40 @@ ssh my-dev-vm
 If an SSH config entry for the VM name already exists, the script prompts
 you to remove it or pick a different `--vm-name`.
 
-### Testing
+### DPLL Unit Tests
+
+`scripts/test-dpll.sh` exercises the DPLL emulation in `netdevsim/dpll.c`.
+It requires root privileges and loaded modules:
+
+```bash
+# Run after DKMS install (modules will be loaded automatically)
+sudo ./scripts/test-dpll.sh
+
+# If modules are already loaded, skip load/unload
+sudo ./scripts/test-dpll.sh --no-load
+
+# Verbose mode (set -x)
+sudo ./scripts/test-dpll.sh --verbose
+```
+
+Or via `make`:
+
+```bash
+make test-dpll
+```
+
+The test suite covers:
+- Module loading (`nsim_dpll`, `netdevsim`)
+- Device creation with `wpc=1` (DPLL activation) and `wpc=0` (no DPLL)
+- Sysfs `lock_status` read/write/transitions/invalid input/rapid cycling
+- Generic netlink DPLL device and pin dump (PPS+EEC devices, GNSS/EXT/SyncE pins)
+- Sysfs-to-netlink lock status consistency
+- GNSS device presence and NMEA echo
+- PTP clock and network interface verification
+- Device teardown and re-creation
+- dmesg sanity (no kernel warnings/errors)
+
+### Testing with UTM
 
 `scripts/test-utm-ubuntu.sh` does the same VM setup plus smoke tests and
 (optionally) the full ptp-operator test suite.

dpll/dpll_core.c

@@ -853,14 +853,67 @@ const struct dpll_pin_ops *dpll_pin_ops(struct dpll_pin_ref *ref)
 	return reg->ops;
 }
 
+/*
+ * On kernels with CONFIG_DPLL=y the built-in DPLL subsystem already
+ * registers a genl family named "dpll".  We need to replace it with
+ * our own so that netdevsim DPLL devices are served by the DKMS code
+ * (which matches the netdevsim driver API exactly).
+ *
+ * Strategy:
+ *   1. Look up the kernel's dpll_nl_family via kprobes
+ *   2. genl_unregister_family() it
+ *   3. genl_register_family() our own (also named "dpll")
+ *   4. On exit, reverse the process
+ */
+
+#include <linux/kprobes.h>
+
+static bool kernel_dpll_hijacked;
+
+typedef unsigned long (*kallsyms_lookup_name_t)(const char *name);
+
+static unsigned long nsim_lookup_name(const char *name)
+{
+	static kallsyms_lookup_name_t fn;
+
+	if (!fn) {
+		struct kprobe kp = { .symbol_name = "kallsyms_lookup_name" };
+		int ret = register_kprobe(&kp);
+
+		if (ret < 0)
+			return 0;
+		fn = (kallsyms_lookup_name_t)kp.addr;
+		unregister_kprobe(&kp);
+	}
+	return fn(name);
+}
+
 static int __init dpll_init(void)
 {
+	unsigned long addr;
 	int ret;
 
+	addr = nsim_lookup_name("dpll_nl_family");
+	if (!addr) {
+		pr_warn("nsim_dpll: cannot find kernel dpll_nl_family\n");
+	} else {
+		const struct genl_family *kfam =
+			(const struct genl_family *)addr;
+
+		ret = genl_unregister_family(kfam);
+		if (ret) {
+			pr_warn("nsim_dpll: failed to unregister kernel dpll family: %d\n", ret);
+		} else {
+			kernel_dpll_hijacked = true;
+			pr_info("nsim_dpll: unregistered kernel built-in dpll genl family\n");
+		}
+	}
+
 	ret = genl_register_family(&dpll_nl_family);
 	if (ret)
 		goto error;
 
+	pr_info("nsim_dpll: registered dpll genl family (replacing kernel built-in)\n");
 	return 0;
 
 error:
@@ -871,10 +924,24 @@ static int __init dpll_init(void)
 static void __exit dpll_exit(void)
 {
 	genl_unregister_family(&dpll_nl_family);
+
+	/*
+	 * We intentionally do NOT re-register the kernel's built-in
+	 * dpll genl family here.  genl_register_family() writes to the
+	 * struct (setting family->id etc.) and the kernel's
+	 * dpll_nl_family is in __ro_after_init memory — writing to it
+	 * causes a fatal page fault on aarch64.
+	 *
+	 * This means the dpll genl family is absent after module
+	 * unload, which is acceptable for CI/test environments.
+	 */
+	if (kernel_dpll_hijacked)
+		pr_info("nsim_dpll: kernel dpll family was hijacked; not restoring (ro_after_init)\n");
+
 	mutex_destroy(&dpll_lock);
 }
 
-subsys_initcall(dpll_init);
+module_init(dpll_init);
 module_exit(dpll_exit);
 
 MODULE_LICENSE("GPL");

dpll/dpll_nl.c

@@ -149,7 +149,7 @@ static const struct genl_multicast_group dpll_nl_mcgrps[] = {
 };
 
 struct genl_family dpll_nl_family __ro_after_init = {
-	.name		= "nsim_dpll",
+	.name		= "dpll",
 	.version	= DPLL_FAMILY_VERSION,
 	.netnsok	= true,
 	.parallel_ops	= true,

include/linux/ptp_mock.h

@@ -16,28 +16,33 @@ struct device;
 struct mock_phc {
 	struct ptp_clock_info info;
 	struct ptp_clock *clock;
-	struct timecounter tc;
-	struct cyclecounter cc;
 	int logical_clk_id;
 	struct kref ref;
 	spinlock_t lock;
+	/* MONOTONIC-based timekeeping (immune to phc2sys stepping REALTIME/TAI) */
+	s64 offset_ns;		/* PHC = CLOCK_MONOTONIC + offset_ns */
+	s64 freq_ppb;		/* rate correction from adjfine */
+	u64 last_mono_ns;	/* CLOCK_MONOTONIC snapshot at last update */
 	/*
-	 * Two pins: index 0 unused, index 1 "GNSS1PPS" — matches common NIC
-	 * layouts and ts2phc defaults (e.g. ts2phc.pin_index 1 on ens1f0).
+	 * E810-style pin layout: GNSS-1PPS input + 4 external connectors.
+	 * Pin index 0 = GNSS-1PPS (ts2phc default), followed by SMA1, SMA2,
+	 * U.FL1, U.FL2 so the dashboard SMA probe discovers them.
 	 */
-	struct ptp_pin_desc pins[2];
+	struct ptp_pin_desc pins[5];
 	/* EXTTS (1PPS) simulation */
 	struct hrtimer extts_timer;
 	bool extts_enabled;
 	int extts_channel;
+	u64 last_extts_sec;	/* dedup: last CLOCK_TAI second we reported */
 };
 
 #if IS_ENABLED(CONFIG_PTP_1588_CLOCK_MOCK)
 
 struct mock_phc *mock_phc_create(struct device *dev, int logical_clk_id);
 int mock_phc_index(struct mock_phc *phc);
-int mock_phc_logical_clk_id(struct mock_phc *phc);	
+int mock_phc_logical_clk_id(struct mock_phc *phc);
 void mock_phc_release(struct mock_phc *phc);
+struct kobject *mock_phc_dev_kobj(struct mock_phc *phc);
 
 struct ptp_clock_info *mock_phc_get_ptp_info(struct mock_phc *phc);
 #else

include/nsim_rename.h

@@ -51,6 +51,7 @@
 #define mock_phc_index			nsim_mock_phc_index
 #define mock_phc_logical_clk_id		nsim_mock_phc_logical_clk_id
 #define mock_phc_get_ptp_info		nsim_mock_phc_get_ptp_info
+#define mock_phc_dev_kobj		nsim_mock_phc_dev_kobj
 
 /* ---- DPLL core (dpll_core.c) ------------------------------------------- */
 #define dpll_device_get			nsim_dpll_device_get