README.scrypt: Document zuikkis kernel

README.scrypt

@@ -99,7 +99,14 @@ all you will need to set.
 
 
 Optional parameters to tune:
-threads, thread-concurrency, lookup-gap
+kernel, threads, thread-concurrency, lookup-gap
+
+kernel:
+This selects the OpenCL code to use. By default, the kernel named "scrypt" will
+be used. BFGMiner also includes Zuikkis's optimised version, which you can use
+with:
+    --set-device OCL:kernel=zuikkis
+Note that this version requires lookup-gap set to 2 (which is default).
 
 thread-concurrency:
 This tunes the optimal size of work that scrypt can do. It is internally tuned
@@ -133,7 +140,7 @@ SUMMARY: Worth playing with once everything else has been tried but will
 probably do nothing.
 
 vectors=XX
-Vectors are NOT used by the scrypt mining kernel.
+Vectors are NOT used by scrypt mining kernels.
 SUMMARY: Does nothing.
 
 

opencl/zuikkis.cl

@@ -28,6 +28,8 @@
  * online backup system.
  */
 
+// kernel-interface: scrypt
+
 __constant uint ES[2] = { 0x00FF00FF, 0xFF00FF00 };
 __constant uint K[] = {
 	0x428a2f98U,