From b2a8c02d1da4bd5aa146489f6f7ed2f7a7ae1a81 Mon Sep 17 00:00:00 2001
From: yabu76 <yabu76@gmail.com>
Date: Thu, 14 Aug 2025 22:18:41 +0900
Subject: [PATCH] Fix incorrect handling of the return value of the poll system
 call

---
 src/misc.c    |  7 ++++++-
 src/xymodem.c | 14 ++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/misc.c b/src/misc.c
index 13d601e..271d266 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -98,12 +98,17 @@ int read_poll(int fd, void *data, size_t len, int timeout)
         if (fds.revents & POLLIN)
         {
             // Read ready data
+            // return value should not be 0
             return read(fd, data, len);
         }
+        else /* if (fds.revents & (POLLERR | POLLHUP | POLLNVAL)) */
+        {
+            return -1;
+        }
     }
 
     /* Timeout */
-    return ret;
+    return 0;
 }
 
 // Function to calculate djb2 hash of string
diff --git a/src/xymodem.c b/src/xymodem.c
index 3b645cc..3b46ef8 100644
--- a/src/xymodem.c
+++ b/src/xymodem.c
@@ -91,6 +91,9 @@ static int xmodem_1k(int sio, const void *data, size_t len, int seq)
         rc = read_poll(sio, &resp, 1, 50);
         if (rc == 0)
         {
+            /* timeout 50 ms
+               resp has last received character beacuse read_poll() doesn't
+               destroy resp value in this case. */
             if (resp == 'C') break;
             if (resp == CAN) return ERR;
             continue;
@@ -232,6 +235,9 @@ static int xmodem(int sio, const void *data, size_t len)
         rc = read_poll(sio, &resp, 1, 50);
         if (rc == 0)
         {
+            /* timeout 50 ms
+               resp has last received character beacuse read_poll() doesn't
+               destroy resp value in this case. */
             if (resp == 'C') break;
             if (resp == CAN) return ERR;
             continue;
@@ -389,6 +395,10 @@ int start_receive(int sio)
             {
                 return rc;
             }
+            else /* if (fds.revents & (POLLERR | POLLHUP | POLLNVAL)) */
+            {
+                return -1;
+            }
         }
         if (key_hit)
             return USER_CAN;
@@ -544,6 +554,10 @@ int receive_packet(int sio, struct xpacket packet, int fd)
             while (read_poll(sio, &dummy, 1, 100) > 0) {}
             return ERR;
         }
+        else /* if (fds.revents & (POLLERR | POLLHUP | POLLNVAL)) */
+        {
+            return ERR;
+        }
     }
 
     uint8_t tester = 0xff;