remote: usb: print "access denied" error

When we get an error with errno 13, it means that the user doesn't
have access to the USB device.  Rather than silently eating this
error and returning -1, print out a message to aid in debugging.

Signed-off-by: Sean Cross <sean@xobs.io>

diff --git a/litex/tools/remote/comm_usb.py b/litex/tools/remote/comm_usb.py
index 53ee4c8182193ddfb0fb807cc7c566fb8cae5e04..302a4e4e4c6197d8bc4a14f111f69bc74ed7cb05 100644 (file)
--- a/litex/tools/remote/comm_usb.py
+++ b/litex/tools/remote/comm_usb.py
@@ -111,7 +111,14 @@ class CommUSB:
             if value is None:
                 raise TypeError
             return int.from_bytes(value, byteorder="little")
-        except (usb.core.USBError, TypeError):
+        except usb.core.USBError as e:
+            if e.errno == 13:
+                print("Access Denied. Maybe try using sudo?")
+            self.close()
+            self.open()
+            if depth < self.MAX_RECURSION_COUNT:
+                return self.usb_read(addr, depth+1)
+        except TypeError:
             self.close()
             self.open()
             if depth < self.MAX_RECURSION_COUNT:
@@ -127,7 +134,7 @@ class CommUSB:
 
     def usb_write(self, addr, value, depth=0):
         try:
-            self.dev.ctrl_transfer(bmRequestType=0x43, bRequest=0x00,
+            value = self.dev.ctrl_transfer(bmRequestType=0x43, bRequest=0x00,
                     wValue=addr & 0xffff,
                     wIndex=(addr >> 16) & 0xffff,
                     data_or_wLength=bytes([(value >> 0) & 0xff,
@@ -135,7 +142,9 @@ class CommUSB:
                                            (value >> 16) & 0xff,
                                            (value >> 24) & 0xff]
                                           ), timeout=None)
-        except usb.core.USBError:
+        except usb.core.USBError as e:
+            if e.errno == 13:
+                print("Access Denied. Maybe try using sudo?")
             self.close()
             self.open()
             if depth < self.MAX_RECURSION_COUNT: