From 15079e78d3cbca7e33bd7f421c00ada20599e495 Mon Sep 17 00:00:00 2001
From: Fahrzin Hemmati <fahhem@gmail.com>
Date: Mon, 18 Apr 2016 22:48:42 +0200
Subject: [PATCH] Add new function ftdi_usb_get_strings2()

This new version of ftdi_usb_get_strings() only closes
the device if it was opened by the function, too.

[minor code and changelog tweaks by Thomas Jarosch]
---
 src/ftdi.c |   71 +++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 src/ftdi.h |   10 ++++++--
 2 files changed, 73 insertions(+), 8 deletions(-)

diff --git a/src/ftdi.c b/src/ftdi.c
index 573080a..529b99e 100644
--- a/src/ftdi.c
+++ b/src/ftdi.c
@@ -406,16 +406,76 @@ void ftdi_list_free2(struct ftdi_device_list *devlist)
     \retval  -9: get serial number failed
     \retval -11: libusb_get_device_descriptor() failed
 */
-int ftdi_usb_get_strings(struct ftdi_context * ftdi, struct libusb_device * dev,
-                         char * manufacturer, int mnf_len, char * description, int desc_len, char * serial, int serial_len)
+int ftdi_usb_get_strings(struct ftdi_context *ftdi,
+                         struct libusb_device *dev,
+                         char *manufacturer, int mnf_len,
+                         char *description, int desc_len,
+                         char *serial, int serial_len)
 {
-    struct libusb_device_descriptor desc;
+    int ret;
 
     if ((ftdi==NULL) || (dev==NULL))
         return -1;
 
     if (ftdi->usb_dev == NULL && libusb_open(dev, &ftdi->usb_dev) < 0)
-            ftdi_error_return(-4, "libusb_open() failed");
+        ftdi_error_return(-4, "libusb_open() failed");
+
+    // ftdi->usb_dev will not be NULL when entering ftdi_usb_get_strings2(), so
+    // it won't be closed either. This allows us to close it whether we actually
+    // called libusb_open() up above or not. This matches the expected behavior
+    // (and note) for ftdi_usb_get_strings().
+    ret = ftdi_usb_get_strings2(ftdi, dev,
+                                manufacturer, mnf_len,
+                                description, desc_len,
+                                serial, serial_len);
+
+    // only close it if it was successful, as all other return codes close
+    // before returning already.
+    if (ret == 0)
+        ftdi_usb_close_internal(ftdi);
+
+    return ret;
+}
+
+/**
+    Return device ID strings from the usb device.
+
+    The parameters manufacturer, description and serial may be NULL
+    or pointer to buffers to store the fetched strings.
+
+    \note The old function ftdi_usb_get_strings() always closes the device.
+          This version only closes the device if it was opened by it.
+
+    \param ftdi pointer to ftdi_context
+    \param dev libusb usb_dev to use
+    \param manufacturer Store manufacturer string here if not NULL
+    \param mnf_len Buffer size of manufacturer string
+    \param description Store product description string here if not NULL
+    \param desc_len Buffer size of product description string
+    \param serial Store serial string here if not NULL
+    \param serial_len Buffer size of serial string
+
+    \retval   0: all fine
+    \retval  -1: wrong arguments
+    \retval  -4: unable to open device
+    \retval  -7: get product manufacturer failed
+    \retval  -8: get product description failed
+    \retval  -9: get serial number failed
+    \retval -11: libusb_get_device_descriptor() failed
+*/
+int ftdi_usb_get_strings2(struct ftdi_context *ftdi, struct libusb_device *dev,
+                          char *manufacturer, int mnf_len,
+                          char *description, int desc_len,
+                          char *serial, int serial_len)
+{
+    struct libusb_device_descriptor desc;
+
+    if ((ftdi==NULL) || (dev==NULL))
+        return -1;
+
+    char need_open = (ftdi->usb_dev == NULL);
+    if (need_open && libusb_open(dev, &ftdi->usb_dev) < 0)
+        ftdi_error_return(-4, "libusb_open() failed");
 
     if (libusb_get_device_descriptor(dev, &desc) < 0)
         ftdi_error_return(-11, "libusb_get_device_descriptor() failed");
@@ -447,7 +507,8 @@ int ftdi_usb_get_strings(struct ftdi_context * ftdi, struct libusb_device * dev,
         }
     }
 
-    ftdi_usb_close_internal (ftdi);
+    if (need_open)
+        ftdi_usb_close_internal (ftdi);
 
     return 0;
 }
diff --git a/src/ftdi.h b/src/ftdi.h
index fa53b29..ca38bbe 100644
--- a/src/ftdi.h
+++ b/src/ftdi.h
@@ -480,9 +480,13 @@ extern "C"
     void ftdi_list_free(struct ftdi_device_list **devlist);
     void ftdi_list_free2(struct ftdi_device_list *devlist);
     int ftdi_usb_get_strings(struct ftdi_context *ftdi, struct libusb_device *dev,
-                             char * manufacturer, int mnf_len,
-                             char * description, int desc_len,
-                             char * serial, int serial_len);
+                             char *manufacturer, int mnf_len,
+                             char *description, int desc_len,
+                             char *serial, int serial_len);
+    int ftdi_usb_get_strings2(struct ftdi_context *ftdi, struct libusb_device *dev,
+                              char *manufacturer, int mnf_len,
+                              char *description, int desc_len,
+                              char *serial, int serial_len);
     int ftdi_eeprom_set_strings(struct ftdi_context *ftdi, char * manufacturer,
                                 char * product, char * serial);
 
-- 
1.7.1