Try using every scale found

Makefile

@@ -1,5 +1,5 @@
 LDLIBS=-lm -lusb-1.0
-CFLAGS=-Os -Wall
+CFLAGS=-Os -Wall -Wextra
 DOCCO=docco
 
 usbscale: usbscale.c scales.h

usbscale.c

@@ -25,6 +25,8 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
+
+#include <stdbool.h>
 #include <stdio.h>
 #include <sys/types.h>
 #include <stdint.h>
@@ -54,10 +56,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define CONTROL_REPORT_SIZE 2
 
 //
-// **find_scale** takes a libusb device list and finds the first USB device
+// **is_scale** takes a libusb device list and finds the first USB device
 // that matches a device listed in scales.h.
 //
-static libusb_device* find_scale(libusb_device**);
+static bool is_scale(libusb_device*);
 //
 // **print_scale_data** takes the 6-byte output from the scale and interprets
 // it, printing out the result to the screen. It also returns a 1 if the
@@ -103,6 +105,7 @@ int main(int argc, char **argv)
     ssize_t cnt;
     libusb_device* dev;
     libusb_device_handle* handle;
+    bool found_scale = false;
 
     int weigh_count = WEIGH_COUNT -1;
 
@@ -127,15 +130,17 @@ int main(int argc, char **argv)
         return (int) cnt;
 
     //
-    // Once we have the list, we use **find_scale** to loop through and match
-    // every device against the scales.h list. **find_scale** will return the
+    // Once we have the list, we use **is_scale** to loop through and match
+    // every device against the scales.h list. **is_scale** will return the
     // first device that matches, or 0 if none of them matched.
     //
-    dev = find_scale(devs);
-    if(dev == 0) {
-        fprintf(stderr, "No USB scale found on this computer.\n");
-        return -1;
+
+    int i = 0;
+    while ((dev = devs[i++]) != NULL) {
+        if (!is_scale(dev)) {
+            continue;
         }
+        found_scale = true;
 
         //
         // Once we have a pointer to the USB scale in question, we open it.
@@ -158,9 +163,9 @@ int main(int argc, char **argv)
         // On Linux, we typically need to detach the kernel driver so that we can
         // handle this USB device. We are a userspace tool, after all.
         //
-#ifdef __linux__
+    #ifdef __linux__
         libusb_detach_kernel_driver(handle, 0);
-#endif
+    #endif
         //
         // Finally, we can claim the interface to this device and begin I/O.
         //
@@ -238,12 +243,12 @@ int main(int argc, char **argv)
             // received to **print_scale_data**.
             //
             if(r == 0) {
-#ifdef DEBUG
+    #ifdef DEBUG
                 int i;
                 for(i = 0; i < WEIGH_REPORT_SIZE; i++) {
                     printf("%x\n", data[i]);
                 }
-#endif
+    #endif
                 if (weigh_count < 1) {
                     scale_result = print_scale_data(data);
                     if(scale_result != 1)
@@ -263,9 +268,9 @@ int main(int argc, char **argv)
         // detached earlier, close the handle to the device, free the device list
         // that we retrieved, and exit libusb.
         //
-#ifdef __linux__
+    #ifdef __linux__
         libusb_attach_kernel_driver(handle, 0);
-#endif
+    #endif
         libusb_close(handle);
         libusb_free_device_list(devs, 1);
         libusb_exit(NULL);
@@ -274,7 +279,18 @@ int main(int argc, char **argv)
         // The return code will be 0 for success or -1 for errors (see
         // `libusb_init` above if it's neither 0 nor -1).
         //
+        if (scale_result != 0) {
             return scale_result;
+        }
+    }
+    //
+    // if no scales were found, make sure to show a message
+    //
+    if(!found_scale) {
+        fprintf(stderr, "No USB scale found on this computer.\n");
+        return -1;
+    }
+    return 0;
 }
 
 //
@@ -372,25 +388,17 @@ static int print_scale_data(unsigned char* dat) {
 }
 
 //
-// find_scale
+// is_scale
 // ----------
 //
-// **find_scale** takes a `libusb_device\*\*` list and loop through it,
+// **is_scale** takes a `libusb_device\*\*` list and loop through it,
 // matching each device's vendor and product IDs to the scales.h list. It
 // return the first matching `libusb_device\*` or 0 if no matching device is
 // found.
 //
-static libusb_device* find_scale(libusb_device **devs)
+static bool is_scale(libusb_device *dev)
 {
 
-    int i = 0;
-    libusb_device* dev = 0;
-
-    //
-    // Loop through each USB device, and for each device, loop through the
-    // scales list to see if it's one of our listed scales.
-    //
-    while ((dev = devs[i++]) != NULL) {
     struct libusb_device_descriptor desc;
     int r = libusb_get_device_descriptor(dev, &desc);
     if (r < 0) {
@@ -434,13 +442,11 @@ static libusb_device* find_scale(libusb_device **devs)
                     "Manufacturer: %s\n", string);
             libusb_close(hand);
 #endif
-                    return dev;
-
+            return true;
             break;
         }
     }
-    }
-    return NULL;
+    return false;
 }
 
 uint8_t get_first_endpoint_address(libusb_device* dev)