>From b21f09ce333704ac57d57840cd2de22e08f52ba2 Mon Sep 17 00:00:00 2001
From: Eugene Hutorny <eugene@hutorny.in.ua>
Date: Sat, 23 Jan 2016 06:41:30 +0200
Subject: [PATCH] Added ftdi_transfer_data_cancel for cancelation of a
 submitted transfer, avoided resubmittion of a cancelled transfer in the
 callbacks, replaced calls to libusb_handle_events with
 libusb_handle_events_timeout_completed (Eugene Hutorny, eugene@hutorny.in.ua)

---
 README     |  5 ++++-
 src/ftdi.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++---------
 src/ftdi.h |  1 +
 3 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/README b/README
index 165330d..18c0521 100644
--- a/README
+++ b/README
@@ -20,6 +20,10 @@ that made libftdi possible what it is today.
 
 Changes
 -------
+* Added ftdi_transfer_data_cancel for cancelation of a submitted transfer,
+  avoided resubmittion of a cancelled transfer in the callbacks, replaced calls
+  to libusb_handle_events with libusb_handle_events_timeout_completed
+  (Eugene Hutorny, eugene@hutorny.in.ua)
 * Support for FT230X devices (Uwe Bonnes)
 * ftdi_usb_get_strings(): Don't try to open an already open device (Denis Sirotkin)
 * Support for finding devices bricked by the Windows driver (Forest Crossman)
@@ -27,7 +31,6 @@ Changes
 * Fix a typo in the MPSSE command CLK_BYTES_OR_LOW (Benjamin Vanheuverzwijn)
 * Minor fixes for MSVC++ (Andrei Errapart)
 * Various small code improvements (Florian Preinstorfer, Jochen Sprickerhof, xantares09)
-
 You'll find the newest version of libftdi at:
 http://www.intra2net.com/en/developer/libftdi
 
diff --git a/src/ftdi.c b/src/ftdi.c
index 1b29468..4cc6b52 100644
--- a/src/ftdi.c
+++ b/src/ftdi.c
@@ -1470,9 +1470,13 @@ static void LIBUSB_CALL ftdi_read_data_cb(struct libusb_transfer *transfer)
             }
         }
     }
-    ret = libusb_submit_transfer (transfer);
-    if (ret < 0)
-        tc->completed = 1;
+    if( transfer->status == LIBUSB_TRANSFER_CANCELLED )
+    	tc->completed = LIBUSB_TRANSFER_CANCELLED;
+    else {
+        ret = libusb_submit_transfer (transfer);
+        if (ret < 0)
+            tc->completed = 1;
+    }
 }
 
 
@@ -1497,9 +1501,13 @@ static void LIBUSB_CALL ftdi_write_data_cb(struct libusb_transfer *transfer)
 
         transfer->length = write_size;
         transfer->buffer = tc->buf + tc->offset;
-        ret = libusb_submit_transfer (transfer);
-        if (ret < 0)
-            tc->completed = 1;
+        if( transfer->status == LIBUSB_TRANSFER_CANCELLED )
+            tc->completed = LIBUSB_TRANSFER_CANCELLED;
+        else {
+            ret = libusb_submit_transfer (transfer);
+            if (ret < 0)
+                tc->completed = 1;
+        }
     }
 }
 
@@ -1662,17 +1670,19 @@ struct ftdi_transfer_control *ftdi_read_data_submit(struct ftdi_context *ftdi, u
 int ftdi_transfer_data_done(struct ftdi_transfer_control *tc)
 {
     int ret;
-
+    struct timeval to = { 0, 0 };
     while (!tc->completed)
     {
-        ret = libusb_handle_events(tc->ftdi->usb_ctx);
+        ret = libusb_handle_events_timeout_completed(tc->ftdi->usb_ctx,
+                &to, &tc->completed);
         if (ret < 0)
         {
             if (ret == LIBUSB_ERROR_INTERRUPTED)
                 continue;
             libusb_cancel_transfer(tc->transfer);
             while (!tc->completed)
-                if (libusb_handle_events(tc->ftdi->usb_ctx) < 0)
+                if (libusb_handle_events_timeout_completed(tc->ftdi->usb_ctx,
+                        &to, &tc->completed) < 0)
                     break;
             libusb_free_transfer(tc->transfer);
             free (tc);
@@ -1696,6 +1706,33 @@ int ftdi_transfer_data_done(struct ftdi_transfer_control *tc)
 }
 
 /**
+    Cancel transfer and wait for completion.
+
+    Use libusb 1.0 asynchronous API.
+
+    \param tc pointer to ftdi_transfer_control
+    \param to pointer to timeout value or NULL for infinite
+*/
+
+void ftdi_transfer_data_cancel(struct ftdi_transfer_control *tc,
+		struct timeval * to)
+{
+	struct timeval tv = { 0, 0 };
+    if ( !tc->completed && tc->transfer != NULL ) {
+		if( to == NULL ) to = &tv;
+		libusb_cancel_transfer(tc->transfer);
+		while (!tc->completed)
+			if ( libusb_handle_events_timeout_completed(
+					tc->ftdi->usb_ctx, to, &tc->completed) < 0)
+				break;
+    }
+    if( tc->transfer )
+    	libusb_free_transfer(tc->transfer);
+    free (tc);
+}
+
+
+/**
     Configure write buffer chunk size.
     Default is 4096.
 
diff --git a/src/ftdi.h b/src/ftdi.h
index 5aaeb6c..829ea37 100644
--- a/src/ftdi.h
+++ b/src/ftdi.h
@@ -520,6 +520,7 @@ extern "C"
 
     struct ftdi_transfer_control *ftdi_read_data_submit(struct ftdi_context *ftdi, unsigned char *buf, int size);
     int ftdi_transfer_data_done(struct ftdi_transfer_control *tc);
+    void ftdi_transfer_data_cancel(struct ftdi_transfer_control *tc, struct timeval * to);
 
     int ftdi_set_bitmode(struct ftdi_context *ftdi, unsigned char bitmask, unsigned char mode);
     int ftdi_disable_bitbang(struct ftdi_context *ftdi);
-- 
2.6.2