From 19c50d4c3db32668b4d5bebfb7e6d15e87cd10f4 Mon Sep 17 00:00:00 2001
From: Dirk Zimoch <dirk.zimoch@psi.ch>
Date: Fri, 5 Jun 2020 16:01:14 +0200
Subject: [PATCH] fix aai and waveform soft device support to support reading
 empty arrays

---
 modules/database/src/std/dev/devAaiSoft.c | 11 ++++++++---
 modules/database/src/std/dev/devWfSoft.c  |  7 +++++--
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/modules/database/src/std/dev/devAaiSoft.c b/modules/database/src/std/dev/devAaiSoft.c
index 1f5765650..0fbb1148e 100644
--- a/modules/database/src/std/dev/devAaiSoft.c
+++ b/modules/database/src/std/dev/devAaiSoft.c
@@ -60,9 +60,10 @@ static long init_record(dbCommon *pcommon)
         }
 
         status = dbLoadLinkArray(plink, prec->ftvl, prec->bptr, &nRequest);
-        if (!status && nRequest > 0) {
+        if (!status) {
             prec->nord = nRequest;
             prec->udf = FALSE;
+            return status;
         }
     }
     return 0;
@@ -74,7 +75,7 @@ static long readLocked(struct link *pinp, void *dummy)
     long nRequest = prec->nelm;
     long status = dbGetLink(pinp, prec->ftvl, prec->bptr, 0, &nRequest);
 
-    if (!status && nRequest > 0) {
+    if (!status) {
         prec->nord = nRequest;
         prec->udf = FALSE;
 
@@ -89,8 +90,12 @@ static long read_aai(aaiRecord *prec)
 {
     epicsUInt32 nord = prec->nord;
     struct link *pinp = prec->simm == menuYesNoYES ? &prec->siol : &prec->inp;
-    long status = dbLinkDoLocked(pinp, readLocked, NULL);
+    long status;
 
+    if (dbLinkIsConstant(pinp))
+        return 0;
+
+    status = dbLinkDoLocked(pinp, readLocked, NULL);
     if (status == S_db_noLSET)
         status = readLocked(pinp, NULL);
 
diff --git a/modules/database/src/std/dev/devWfSoft.c b/modules/database/src/std/dev/devWfSoft.c
index 0a089b831..29a617be3 100644
--- a/modules/database/src/std/dev/devWfSoft.c
+++ b/modules/database/src/std/dev/devWfSoft.c
@@ -41,7 +41,7 @@ static long init_record(dbCommon *pcommon)
     long nelm = prec->nelm;
     long status = dbLoadLinkArray(&prec->inp, prec->ftvl, prec->bptr, &nelm);
 
-    if (!status && nelm > 0) {
+    if (!status) {
         prec->nord = nelm;
         prec->udf = FALSE;
     }
@@ -77,11 +77,14 @@ static long read_wf(waveformRecord *prec)
     rt.ptime = (dbLinkIsConstant(&prec->tsel) &&
         prec->tse == epicsTimeEventDeviceTime) ? &prec->time : NULL;
 
+    if (dbLinkIsConstant(&prec->inp))
+        return 0;
+
     status = dbLinkDoLocked(&prec->inp, readLocked, &rt);
     if (status == S_db_noLSET)
         status = readLocked(&prec->inp, &rt);
 
-    if (!status && rt.nRequest > 0) {
+    if (!status) {
         prec->nord = rt.nRequest;
         prec->udf = FALSE;
         if (nord != prec->nord)