From 33f903178e7567f4ece8da31743a279e829235d8 Mon Sep 17 00:00:00 2001
From: SPRESENSE <41312067+SPRESENSE@users.noreply.github.com>
Date: Mon, 24 Oct 2022 11:28:25 +0900
Subject: [PATCH] drivers/modem/alt1250: Fix poll function

Notify only when there are available events.
---
 drivers/modem/alt1250/alt1250.c | 52 +++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/drivers/modem/alt1250/alt1250.c b/drivers/modem/alt1250/alt1250.c
index 972fea97ff..ee093d47ea 100644
--- a/drivers/modem/alt1250/alt1250.c
+++ b/drivers/modem/alt1250/alt1250.c
@@ -279,6 +279,25 @@ static void write_evtbitmapwithlist(FAR struct alt1250_dev_s *dev,
   nxmutex_unlock(&dev->evtmaplock);
 }
 
+/****************************************************************************
+ * Name: is_evtbitmap_avail
+ ****************************************************************************/
+
+static int is_evtbitmap_avail(FAR struct alt1250_dev_s *dev)
+{
+  int ret;
+
+  nxmutex_lock(&dev->evtmaplock);
+
+  /* 0 means it is not available, otherwise it is available. */
+
+  ret = (0ULL != dev->evtbitmap);
+
+  nxmutex_unlock(&dev->evtmaplock);
+
+  return ret;
+}
+
 /****************************************************************************
  * Name: add_evtbuff
  ****************************************************************************/
@@ -1195,6 +1214,7 @@ static int alt1250_poll(FAR struct file *filep, FAR struct pollfd *fds,
 {
   FAR struct inode *inode;
   FAR struct alt1250_dev_s *dev;
+  int ret = OK;
 
   /* Get our private data structure */
 
@@ -1204,12 +1224,40 @@ static int alt1250_poll(FAR struct file *filep, FAR struct pollfd *fds,
   dev = (FAR struct alt1250_dev_s *)inode->i_private;
   DEBUGASSERT(dev);
 
+  /* Are we setting up the poll?  Or tearing it down? */
+
   if (setup)
     {
-       poll_notify(&fds, 1, POLLIN);
+      /* Ignore waits that do not include POLLIN */
+
+      if ((fds->events & POLLIN) == 0)
+        {
+          ret = -EDEADLK;
+          goto errout;
+        }
+
+      nxmutex_lock(&dev->pfdlock);
+
+      if (is_evtbitmap_avail(dev))
+        {
+          poll_notify(&fds, 1, POLLIN);
+        }
+      else
+        {
+          dev->pfd = fds;
+        }
+
+      nxmutex_unlock(&dev->pfdlock);
+    }
+  else
+    {
+      nxmutex_lock(&dev->pfdlock);
+      dev->pfd = NULL;
+      nxmutex_unlock(&dev->pfdlock);
     }
 
-  return OK;
+errout:
+  return ret;
 }
 
 /****************************************************************************