libftdi Archives

Subject: ftdi_write_data_submit and empty transfers

From: Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Thu, 19 Jul 2018 11:10:46 +0200
Hello,

can anybody comment on the appended patchset.
After adding an empty transfer in the async example, only the first run
succeeds. After adding a case for empty transfers with the second patch,
consecutive runs of the sync example succeed.

Bye
-- 
Uwe Bonnes                bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------
>From 4da9e37309058ace7c354b7ac109c69df7678afa Mon Sep 17 00:00:00 2001
From: Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 18 Jul 2018 21:35:19 +0200
Subject: examples/async.c: Test empty write transfer.

Running "async -b" will fail after the first run.
---
 examples/async.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/examples/async.c b/examples/async.c
index 0589479..9143155 100644
--- a/examples/async.c
+++ b/examples/async.c
@@ -132,7 +132,7 @@ int main(int argc, char **argv)
     struct ftdi_transfer_control *tc_write;
     uint8_t data[3];
     if (do_read) {
-        tc_read = ftdi_read_data_submit(ftdi, data, DATA_TO_READ);
+        tc_read = ftdi_read_data_submit(ftdi, data, DATA_TO_READ - 1);
     }
     if (do_write) {
         tc_write = ftdi_write_data_submit(ftdi, ftdi_init, sizeof(ftdi_init));
@@ -140,6 +140,12 @@ int main(int argc, char **argv)
         if (transfer != sizeof(ftdi_init)) {
             printf("Async write failed : %d\n", transfer);
         }
+        /* Test empty transfer.*/
+        tc_write = ftdi_write_data_submit(ftdi, ftdi_init, 0);
+        transfer = ftdi_transfer_data_done(tc_write);
+        if (transfer != 0) {
+            printf("Async empty write failed : %d\n", transfer);
+        }
     } else {
         int written = ftdi_write_data(ftdi, ftdi_init, sizeof(ftdi_init));
         if (written != sizeof(ftdi_init)) {
@@ -148,17 +154,23 @@ int main(int argc, char **argv)
     }
     if (do_read) {
         int transfer = ftdi_transfer_data_done(tc_read);
-        if (transfer != DATA_TO_READ) {
+        if (transfer != DATA_TO_READ - 1) {
             printf("Async Read failed:%d\n", transfer);
         }
+        /* Test splitted read transfer.*/
+        tc_read = ftdi_read_data_submit(ftdi, data + DATA_TO_READ - 1, 1);
+        transfer = ftdi_transfer_data_done(tc_read);
+        if (transfer != 1) {
+            printf("Async Read remainder failed:%d\n", transfer);
+        }
     } else {
         int index = 0;
-        ftdi->usb_read_timeout = 1;
-        int i = 1000; /* Fail if read did not succeed in 1 second.*/
+        ftdi->usb_read_timeout = 10;
+        int i = 100; /* Fail if read did not succeed in 1 second.*/
         while (i--) {
             int res = ftdi_read_data(ftdi, data + index, 3 - index);
             if (res < 0) {
-                printf("Async read failure at %d\n", index);
+                printf("Sync read timeout at %d\n", index);
             } else {
                 index += res;
             }
-- 
2.13.7

>From 89d9684fd4dfde0fdc6d11f7ee957383b39aa954 Mon Sep 17 00:00:00 2001
From: Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 18 Jul 2018 21:35:40 +0200
Subject: ftdi_write_data_submit: Handle empty transfers.

---
 src/ftdi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/ftdi.c b/src/ftdi.c
index 52266d0..e2efc3a 100644
--- a/src/ftdi.c
+++ b/src/ftdi.c
@@ -1660,6 +1660,12 @@ struct ftdi_transfer_control 
*ftdi_write_data_submit(struct ftdi_context *ftdi,
     if (!tc)
         return NULL;
 
+    if (!size) {
+        tc->completed = 1;
+        tc->offset = 0;
+        tc->transfer = 0;
+        return tc;
+    }
     transfer = libusb_alloc_transfer(0);
     if (!transfer)
     {
-- 
2.13.7


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