Starting with Linux 4.8 the SD/MMC OCR is shown also in /sys, so cache

it if present.

DiscImageChef.Devices/Device/Commands.cs

@@ -171,6 +171,19 @@ namespace DiscImageChef.Devices
                 return 0;
             }
 
+            if((command == (MmcCommands)SecureDigitalCommands.SendOperatingCondition ||
+                command == MmcCommands.SendOpCond) && cachedOcr != null)
+            {
+                System.DateTime start = System.DateTime.Now;
+                buffer = new byte[cachedOcr.Length];
+                System.Array.Copy(cachedOcr, buffer, buffer.Length);
+                response = new uint[4];
+                sense = false;
+                System.DateTime end = System.DateTime.Now;
+                duration = (end - start).TotalMilliseconds;
+                return 0;
+            }
+
             return Command.SendMmcCommand(platformID, fd, command, write, isApplication, flags, argument, blockSize, blocks,
                                           ref buffer, out response, out duration, out sense, timeout);
         }

DiscImageChef.Devices/Device/Constructor.cs

@@ -211,6 +211,12 @@ namespace DiscImageChef.Devices
                         if(len == 0)
                             cachedScr = null;
                     }
+                    if(System.IO.File.Exists("/sys/block/" + devPath + "/device/ocr"))
+                    {
+                        int len = ConvertFromHexASCII("/sys/block/" + devPath + "/device/ocr", out cachedOcr);
+                        if(len == 0)
+                            cachedOcr = null;
+                    }
 
                     if(cachedCid != null)
                     {

DiscImageChef.Devices/Device/Variables.cs

@@ -67,6 +67,7 @@ namespace DiscImageChef.Devices
         readonly byte[] cachedCsd;
         readonly byte[] cachedCid;
         readonly byte[] cachedScr;
+        readonly byte[] cachedOcr;
 
         /// <summary>
         /// Gets the Platform ID for this device