--- src/rhd_acpi.c.orig	2009-10-06 07:36:07.000000000 -0400
+++ src/rhd_acpi.c	2009-10-28 22:07:59.000000000 -0400
@@ -47,6 +47,89 @@
 #include "rhd_acpi.h"
 
 
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+
+#include <stdlib.h>
+#include <sys/sysctl.h>
+
+#define	ACPI_VIDEO_LEVELS	"hw.acpi.video.lcd0.levels"
+#define	ACPI_VIDEO_BRIGHTNESS	"hw.acpi.video.lcd0.brightness"
+
+#define	RHD_BL_NORMALIZE(x, y)	((x) * (RHD_BACKLIGHT_PROPERTY_MAX + 1) / (y))
+#define	RHD_BL_ROUNDDOWN(x, y)	(((x) / (y)) * (y))
+
+/*
+ * Get/Set LCD backlight brightness via acpi_video(4).
+ */
+static Bool
+rhdDoBacklight(struct rhdOutput *Output, Bool do_write, int *val)
+{
+    int *levels;
+    size_t len;
+    int level;
+    int max_levels, num_levels;
+    int d1, d2, max, min;
+    int lower, step;
+    int i;
+    RHDFUNC(Output);
+
+    if (sysctlbyname(ACPI_VIDEO_LEVELS, NULL, &len, NULL, 0) != 0 || len == 0)
+	return FALSE;
+    levels = (int *)malloc(len);
+    if (levels == NULL)
+	return FALSE;
+    if (sysctlbyname(ACPI_VIDEO_LEVELS, levels, &len, NULL, 0) != 0) {
+	free(levels);
+	return FALSE;
+    }
+
+    num_levels = len / sizeof(*levels);
+    for (i = 1, max = 0, min = 0; i < num_levels; i++) {
+	if (levels[i] < levels[min])
+	    min = i;
+	if (levels[i] > levels[max])
+	    max = i;
+    }
+    max_levels = levels[max] - levels[min] + 1;
+    step = RHD_BL_NORMALIZE(1, max_levels);
+
+    if (do_write) {
+	if (*val >= RHD_BL_ROUNDDOWN(RHD_BACKLIGHT_PROPERTY_MAX, step)) {
+	    level = levels[max];
+	    free(levels);
+	} else {
+	    d1 = RHD_BACKLIGHT_PROPERTY_MAX;
+	    lower = RHD_BL_ROUNDDOWN(*val, step);
+	    for (i = 0; i < num_levels; i++) {
+		if (RHD_BL_NORMALIZE(levels[i], max_levels) >= lower) {
+		    d2 = RHD_BL_NORMALIZE(levels[i], max_levels) - lower;
+		    if (d1 > d2) {
+			level = levels[i];
+			d1 = d2;
+		    }
+		}
+	    }
+	    free(levels);
+	    if (d1 >= RHD_BACKLIGHT_PROPERTY_MAX)
+		return FALSE;
+	}
+	if (sysctlbyname(ACPI_VIDEO_BRIGHTNESS, NULL, 0, &level, sizeof(level)) != 0)
+	    return FALSE;
+	RHDDebug(Output->scrnIndex, "%s: Wrote value %i (ACPI %i)\n", __func__, *val, level);
+    } else {
+	free(levels);
+	len = sizeof(level);
+	if (sysctlbyname(ACPI_VIDEO_BRIGHTNESS, &level, &len, NULL, 0) != 0)
+	    return FALSE;
+	*val = RHD_BL_NORMALIZE(level, max_levels) + step - 1;
+	RHDDebug(Output->scrnIndex, "%s: Read value %i (ACPI %i)\n", __func__, *val, level);
+    }
+
+    return TRUE;
+}
+
+#elif defined(__linux__)
+
 #define ACPI_PATH "/sys/class/backlight"
 
 /*
@@ -120,6 +203,7 @@
 
     return FALSE;
 }
+#endif
 
 /*
  * RhdACPIGetBacklightControl(): return backlight value in range 0..255;
@@ -128,7 +212,7 @@
 int
 RhdACPIGetBacklightControl(struct rhdOutput *Output)
 {
-#ifdef __linux__
+#if defined(__FreeBSD__) || defined(__DragonFly__) || defined(__linux__)
     int ret;
     RHDFUNC(Output);
     if (rhdDoBacklight(Output, FALSE, &ret))
@@ -144,7 +228,7 @@
 RhdACPISetBacklightControl(struct rhdOutput *Output, int val)
 {
     RHDFUNC(Output);
-#ifdef __linux__
+#if defined(__FreeBSD__) || defined(__DragonFly__) || defined(__linux__)
     rhdDoBacklight(Output, TRUE, &val);
 #endif
 }