linux-kernel - [PATCH 1/4] powerpc/rtas: Handle special return format for RTAS_FN_IBM_OPEN

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Message-ID: <20251205094510.4671-2-nnmlinux@linux.ibm.com>
Date: Fri,  5 Dec 2025 03:45:07 -0600
From: Narayana Murty N <nnmlinux@...ux.ibm.com>
To: mahesh@...ux.ibm.com, maddy@...ux.ibm.com, mpe@...erman.id.au,
        christophe.leroy@...roup.eu, gregkh@...uxfoundation.org,
        oohall@...il.com, npiggin@...il.com
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        tyreld@...ux.ibm.com, vaibhav@...ux.ibm.com, sbhat@...ux.ibm.com,
        ganeshgr@...ux.ibm.com, sourabhjain@...ux.ibm.com
Subject: [PATCH 1/4] powerpc/rtas: Handle special return format for RTAS_FN_IBM_OPEN_ERRINJCT

RTAS_FN_IBM_OPEN_ERRINJCT returns results in special format:
  rets[0] = session token (output)
  rets[1] = status code
  rets[2..] = additional outputs (if any)

Unlike standard RTAS calls where:
  rets[0] = status code
  rets[1..] = outputs

This patch adds special handling for OPEN_ERRINJCT to:
1. Check correct status position (rets[1]) for __fetch_rtas_last_error()
2. Copy all rets[0..nret-1] to outputs[] (including token at rets[0])
3. Return status from rets[1] instead of rets[0]

Reference: OpenPOWER PAPR documentation
	   https://files.openpower.foundation/s/XFgfMaqLMD5Bcm8
Signed-off-by: Narayana Murty N <nnmlinux@...ux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 8d81c1e7a8db..04c8438aadda 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1183,7 +1183,7 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
 	unsigned long flags;
 	struct rtas_args *args;
 	char *buff_copy = NULL;
-	int ret;
+	int ret = 0;
 
 	if (!rtas.entry || token == RTAS_UNKNOWN_SERVICE)
 		return -1;
@@ -1213,15 +1213,33 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
 	va_rtas_call_unlocked(args, token, nargs, nret, list);
 	va_end(list);
 
+	/* Special handling for RTAS_FN_IBM_OPEN_ERRINJCT for error fetching */
 	/* A -1 return code indicates that the last command couldn't
 	   be completed due to a hardware error. */
-	if (be32_to_cpu(args->rets[0]) == -1)
+
+	if (token == rtas_function_token(RTAS_FN_IBM_OPEN_ERRINJCT) && nret > 1)
+		ret = be32_to_cpu(args->rets[1]);
+	else if (nret > 0)
+		ret = be32_to_cpu(args->rets[0]);
+
+	if (ret == -1)
 		buff_copy = __fetch_rtas_last_error(NULL);
 
-	if (nret > 1 && outputs != NULL)
-		for (i = 0; i < nret-1; ++i)
-			outputs[i] = be32_to_cpu(args->rets[i + 1]);
-	ret = (nret > 0) ? be32_to_cpu(args->rets[0]) : 0;
+	/* Handle outputs and return status */
+	if (nret > 1 && outputs != NULL) {
+		if (token == rtas_function_token(RTAS_FN_IBM_OPEN_ERRINJCT)) {
+			/* Special case: rets[0]=token, rets[1]=status, rets[2..]=outputs */
+			for (i = 0; i < nret; ++i)
+				outputs[i] = be32_to_cpu(args->rets[i]);
+		} else {
+			/* Normal case: rets[0]=status, rets[1..]=outputs */
+			for (i = 0; i < nret - 1; ++i)
+				outputs[i] = be32_to_cpu(args->rets[i + 1]);
+		}
+	} else {
+		/* No outputs: just ret is status */
+		ret = (nret > 0) ? be32_to_cpu(args->rets[0]) : 0;
+	}
 
 	lockdep_unpin_lock(&rtas_lock, cookie);
 	raw_spin_unlock_irqrestore(&rtas_lock, flags);
-- 
2.51.1