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diff --git a/comedi/drivers/8253.h b/comedi/drivers/8253.h
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+/*
+    comedi/drivers/8253.h
+    Header file for 8253
+
+    COMEDI - Linux Control and Measurement Device Interface
+    Copyright (C) 2000 David A. Schleef <ds@stm.lbl.gov>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#ifndef _8253_H
+#define _8253_H
+
+extern int i8253_osc_base;
+
+#define i8253_cascade_ns_to_timer i8253_cascade_ns_to_timer_power
+
+static inline void i8253_cascade_ns_to_timer_2div(int *d1, int *d2, int *nanosec, int round_mode)
+{
+       int divider;
+       int div1, div2;
+       int div1_glb, div2_glb, ns_glb;
+       int div1_lub, div2_lub, ns_lub;
+       int ns;
+
+       divider = (*nanosec + i8253_osc_base / 2) / i8253_osc_base;
+
+       /* find 2 integers 1<={x,y}<=65536 such that x*y is
+          close to divider */
+
+       div1_lub = div2_lub = 0;
+       div1_glb = div2_glb = 0;
+
+       ns_glb = 0;
+       ns_lub = 0xffffffff;
+
+       div2 = 0x10000;
+       for (div1 = divider / 65536 + 1; div1 < div2; div1++) {
+               div2 = divider / div1;
+
+               ns = i8253_osc_base * div1 * div2;
+               if (ns <= *nanosec && ns > ns_glb) {
+                       ns_glb = ns;
+                       div1_glb = div1;
+                       div2_glb = div2;
+               }
+
+               div2++;
+               if (div2 <= 65536) {
+                       ns = i8253_osc_base * div1 * div2;
+                       if (ns > *nanosec && ns < ns_lub) {
+                               ns_lub = ns;
+                               div1_lub = div1;
+                               div2_lub = div2;
+                       }
+               }
+       }
+
+       *d1 = div1_lub;
+       *d2 = div2_lub;
+}
+
+static inline void i8253_cascade_ns_to_timer_power(int *d1, int *d2, int *nanosec, int round_mode)
+{
+       int div1, div2;
+       int base;
+
+       for (div1 = 1; div1 <= (1 << 16); div1 <<= 1) {
+               base = i8253_osc_base * div1;
+               switch (round_mode) {
+               case TRIG_ROUND_NEAREST:
+               default:
+                       div2 = (*nanosec + base / 2) / base;
+                       break;
+               case TRIG_ROUND_DOWN:
+                       div2 = (*nanosec) / base;
+                       break;
+               case TRIG_ROUND_UP:
+                       div2 = (*nanosec + base - 1) / base;
+                       break;
+               }
+               if (div2 <= 65536) {
+                       *nanosec = div2 * base;
+                       *d1 = div1 & 0xffff;
+                       *d2 = div2 & 0xffff;
+                       return;
+               }
+       }
+
+       /* shouldn't get here */
+       div1 = 0x10000;
+       div2 = 0x10000;
+       *nanosec = div1 * div2 * i8253_osc_base;
+       *d1 = div1 & 0xffff;
+       *d2 = div2 & 0xffff;
+}
+
+
+#endif
+