From b6f6d34606316f6511dfce2a496ea0953876b50a Mon Sep 17 00:00:00 2001
From: Shu Chen <chenshu@espressif.com>
Date: Fri, 15 May 2026 22:31:14 +0800
Subject: [PATCH] [diag] invoke SetDiagMode before setting channel/power
 (#12941)
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In Host + RCP mode, running `diag start` from the host CLI may trigger
RadioSpinel warnings: InvalidState, “Error processing result” / “Error
waiting response”.

**Root cause**

Diags::ProcessStart sent channel / power commands before enabling diag
mode. On Spinel, these are forwarded to the RCP (via
`SPINEL_PROP_NEST_STREAM_MFG`), but the RCP only accepts other diag
commands after start.

```
    if (!IsEnabled() && !StringMatch(aArgs[0], "start"))
    {
        Output("diagnostics mode is disabled\r\n");
        ExitNow(error = kErrorInvalidState);
    }
```

As a result, early channel / power commands are rejected with
InvalidState.
---
 src/core/diags/factory_diags.cpp | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/core/diags/factory_diags.cpp b/src/core/diags/factory_diags.cpp
index f9658e56f..307176489 100644
--- a/src/core/diags/factory_diags.cpp
+++ b/src/core/diags/factory_diags.cpp
@@ -491,19 +491,24 @@ Error Diags::ProcessStart(uint8_t aArgsLength, char *aArgs[])
     VerifyOrExit(!Get<ThreadNetif>().IsUp(), error = kErrorInvalidState);
 #endif
 
+    mStats.Clear();
+    IgnoreError(Get<Radio>().Enable());
+    Get<Radio>().SetDiagMode(true);
     otPlatDiagChannelSet(mChannel);
     otPlatDiagTxPowerSet(mTxPower);
 
-    IgnoreError(Get<Radio>().Enable());
     Get<Radio>().SetPromiscuous(true);
     Get<Mac::SubMac>().SetRxOnWhenIdle(true);
     otPlatAlarmMilliStop(&GetInstance());
     SuccessOrExit(error = Get<Radio>().Receive(mChannel));
     SuccessOrExit(error = Get<Radio>().SetTransmitPower(mTxPower));
-    Get<Radio>().SetDiagMode(true);
-    mStats.Clear();
 
 exit:
+    if (error != kErrorNone)
+    {
+        Get<Radio>().SetDiagMode(false);
+    }
+
     return error;
 }