Merge pull request #521 from xlz/usb-troubleshooting

Usb troubleshooting docs, closes #516.

Author: floe

README.md

@@ -72,11 +72,21 @@ Messages in `dmesg` like this means bugs in the USB driver. Updating kernel migh
 [  509.238580] xhci_hcd 0000:03:00.0: Assuming host is dying, halting host.
 ```
 
+`failed to submit transfer: LIBUSB_ERROR_IO` followed by `dmesg` messages
+```
+[ 1417.271120] kinect2_bridge: page allocation failure: order:7, mode:0x40d0
+...
+[ 1417.271230]  [<ffffffff815e8f93>] proc_do_submiturb+0x5c3/0xbc0
+[ 1417.271235]  [<ffffffff815ea088>] usbdev_do_ioctl+0xaf8/0xfb0
+
+```
+means USB buffer allocation fails due to memory fragmentation. Reserve memory `sudo sysctl -w vm.min_free_kbytes=65536` or more (always less than 5% of total memory) to mitigate this.
+
 Windows 7 does not have great USB 3.0 drivers. In our testing the above known working devices will stop working after running for a while. However, the official Kinect v2 SDK does not support Windows 7 at all, so there is still hope for Windows 7 users. Windows 8.1 and 10 have improved USB 3.0 drivers.
 
 Disabling USB selective suspend/autosuspend might be helpful to ameliorate transfer problems.
 
-When you report USB issues, please attach relevant debug log from running the program with environment variable `LIBUSB_DEBUG=4`, and relevant log from `dmesg`.
+When you report USB issues, please attach relevant debug log from running the program with environment variable `LIBUSB_DEBUG=3`, and relevant log from `dmesg`.
 
 ### I'm seeing the color camera stream, but no depth/IR (black windows).
 

cmake_modules/FindLibUSB.cmake

@@ -16,7 +16,7 @@ IF(PKG_CONFIG_FOUND)
     SET(MODULE "libusb-1.0>=1.0.20")
   ENDIF()
   IF(LibUSB_FIND_REQUIRED)
-    SET(LisUSB_REQUIRED "REQUIRED")
+    SET(LibUSB_REQUIRED "REQUIRED")
   ENDIF()
   PKG_CHECK_MODULES(LibUSB ${LibUSB_REQUIRED} ${MODULE})
 

src/transfer_pool.cpp

@@ -108,7 +108,7 @@ void TransferPool::submit(size_t num_parallel_transfers)
   }
 
   if (failcount == num_parallel_transfers)
-    LOG_ERROR << "all submissions failed. Try debugging with environment variable: LIBUSB_DEBUG=4.";
+    LOG_ERROR << "all submissions failed. Try debugging with environment variable: LIBUSB_DEBUG=3.";
 }
 
 void TransferPool::cancel()

src/usb_control.cpp

@@ -190,7 +190,7 @@ UsbControl::~UsbControl()
 }
 
 #define CHECK_LIBUSB_RESULT(__CODE, __RESULT) if((__CODE = (__RESULT == LIBUSB_SUCCESS ? Success : Error)) == Error) LOG_ERROR
-#define WRITE_LIBUSB_ERROR(__RESULT) libusb_error_name(__RESULT) << " " << libusb_strerror((libusb_error)__RESULT) << ". Try debugging with environment variable: export LIBUSB_DEBUG=4 ."
+#define WRITE_LIBUSB_ERROR(__RESULT) libusb_error_name(__RESULT) << " " << libusb_strerror((libusb_error)__RESULT) << ". Try debugging with environment variable: export LIBUSB_DEBUG=3 ."
 
 UsbControl::ResultCode UsbControl::setConfiguration()
 {