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From 63857964e14bbf4bcb91eaa56ca46a30d14934ed Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Thu, 18 May 2017 09:21:19 +0200
Subject: [PATCH 06/18] char/serial: Fix emptyness handling

RH-Author: Fam Zheng <famz@redhat.com>
Message-id: <20170518092131.16571-7-famz@redhat.com>
Patchwork-id: 75298
O-Subject: [RHEL-7.4 qemu-kvm PATCH v3 06/18] char/serial: Fix emptyness handling
Bugzilla: 1451470
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>

From: Don Slutz <dslutz@verizon.com>

The commit 88c1ee73d3231c74ff90bcfc084a7589670ec244
char/serial: Fix emptyness check

Still causes extra NULL byte(s) to be sent.

So if the fifo is empty, do not send an extra NULL byte.

Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Don Slutz <dslutz@verizon.com>
Message-id: 1395160174-16006-1-git-send-email-dslutz@verizon.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
(cherry picked from commit dffacd4654ec8bf2898aed230852154c6ed755ed)
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/char/serial.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/char/serial.c b/hw/char/serial.c
index 489a885..e020b0e 100644
--- a/hw/char/serial.c
+++ b/hw/char/serial.c
@@ -225,8 +225,10 @@ static gboolean serial_xmit(GIOChannel *chan, GIOCondition cond, void *opaque)
 
     if (s->tsr_retry <= 0) {
         if (s->fcr & UART_FCR_FE) {
-            s->tsr = fifo8_is_empty(&s->xmit_fifo) ?
-                        0 : fifo8_pop(&s->xmit_fifo);
+            if (fifo8_is_empty(&s->xmit_fifo)) {
+                return FALSE;
+            }
+            s->tsr = fifo8_pop(&s->xmit_fifo);
             if (!s->xmit_fifo.num) {
                 s->lsr |= UART_LSR_THRE;
             }
-- 
1.8.3.1