From 6f37ca3a1e8c18df1809b5aaf0af454b2e2daa56 Mon Sep 17 00:00:00 2001
From: Luca Toniolo <10792599+grandixximo@users.noreply.github.com>
Date: Tue, 5 May 2026 21:33:53 +0800
Subject: [PATCH] task -unhome VOLATILE_HOME joints on any motion-disable edge

Issue #3954: with VOLATILE_HOME=1, tripping a limit switch (or hitting
amp-fault, following error, etc.) disables the drives but leaves all
joints flagged as homed. Only ESTOP and machine-off paths cleared the
homed flag; every other drive-disable cause silently kept it set.

Detect the traj.enabled 1->0 edge in the task main loop and call
emcJointUnhome(-2) so volatile_home joints are unhomed regardless of
which fault path disabled motion.
---
 src/emc/task/emctaskmain.cc | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/emc/task/emctaskmain.cc b/src/emc/task/emctaskmain.cc
index 1d709157425..3bf13a702d1 100644
--- a/src/emc/task/emctaskmain.cc
+++ b/src/emc/task/emctaskmain.cc
@@ -3295,6 +3295,7 @@ int main(int argc, char *argv[])
     }
     while (!done) {
         static int gave_soft_limit_message = 0;
+        static int prev_traj_enabled = 0;
         task_beat++;  // Task's heartbeat
 
         check_ini_hal_items(emcStatus->motion.traj.joints);
@@ -3314,6 +3315,14 @@ int main(int argc, char *argv[])
 	// update subordinate status
 
 	emcMotionUpdate(&emcStatus->motion);
+	// On a motion enabled -> disabled edge (limit switch, amp fault,
+	// following error, etc.) unhome joints marked VOLATILE_HOME. The estop
+	// and machine-off paths already do their own unhome; this catches the
+	// remaining drive-disable causes that don't flip task state.
+	if (prev_traj_enabled && !emcStatus->motion.traj.enabled) {
+	    emcJointUnhome(-2); // only those joints which are volatile_home
+	}
+	prev_traj_enabled = emcStatus->motion.traj.enabled;
 	// synchronize subordinate states
 	if (emcStatus->io.aux.estop) {
 	    if (emcStatus->motion.traj.enabled) {