HID : read-only device access fallback when read/write fails

device/hid/hid_connection_linux.cc

 // Copyright (c) 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "device/hid/hid_connection_linux.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <libudev.h>
 #include <linux/hidraw.h>
@@ skipping 46 matching lines @@
     LOG(ERROR) << "Cannot open HID device as hidraw device.";
     return;
   }
 
   int flags = base::File::FLAG_OPEN |
               base::File::FLAG_READ |
               base::File::FLAG_WRITE;
 
   base::File device_file(base::FilePath(dev_node), flags);
   if (!device_file.IsValid()) {
-    LOG(ERROR) << device_file.error_details();
-    return;
+    base::File::Error file_error = device_file.error_details();
+
+    if (file_error == base::File::FILE_ERROR_ACCESS_DENIED) {
+      flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
+
+      base::File device_file(base::FilePath(dev_node), flags);
+      if (!device_file.IsValid()) {
+        LOG(ERROR) << device_file.error_details();
+        return;
+      }
+    } else {
+      LOG(ERROR) << file_error;
+      return;
+    }
   }
   if (fcntl(device_file.GetPlatformFile(), F_SETFL,
             fcntl(device_file.GetPlatformFile(), F_GETFL) | O_NONBLOCK)) {
     PLOG(ERROR) << "Failed to set non-blocking flag to device file.";
     return;
   }
   device_file_ = device_file.Pass();
 
   if (!base::MessageLoopForIO::current()->WatchFileDescriptor(
       device_file_.GetPlatformFile(),
@@ skipping 159 matching lines @@
         return true;
       }
     }
   }
 
   return false;
 }
 
 }  // namespace device