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Subject: [PATCH] Test: Improve radeonfb mode setting on CRT
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Linux Kernel list <linux-kernel@vger.kernel.org>,
       Linux Fbdev development list 
	<linux-fbdev-devel@lists.sourceforge.net>
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Date: Sun, 13 Mar 2005 10:56:10 +1100
Message-Id: <1110671770.19810.57.camel@gaston>
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Hi !

Recent radeonfb's tend to be a bit anal with accepting or refusing a
mode on a CRT since they expect exact resolution, which doesn't really
happen with fbcon.

This patch reworks the mode matching function to fix that issue, but I
didn't have a chance to test it, so feedback appreciated.

Index: linux-work/drivers/video/aty/radeon_monitor.c
===================================================================
--- linux-work.orig/drivers/video/aty/radeon_monitor.c	2005-03-11 16:54:25.000000000 +1100
+++ linux-work/drivers/video/aty/radeon_monitor.c	2005-03-11 16:58:04.000000000 +1100
@@ -903,7 +903,7 @@
  */
 
 /*
- * This is used when looking for modes. We assign a "goodness" value
+ * This is used when looking for modes. We assign a "distance" value
  * to a mode in the modedb depending how "close" it is from what we
  * are looking for.
  * Currently, we don't compare that much, we could do better but
@@ -912,13 +912,11 @@
 static int radeon_compare_modes(const struct fb_var_screeninfo *var,
 				const struct fb_videomode *mode)
 {
-	int goodness = 0;
+	int distance = 0;
 
-	if (var->yres == mode->yres)
-		goodness += 10;
-	if (var->xres == mode->xres)
-		goodness += 9;
-	return goodness;
+	distance = mode->yres - var->yres;
+	distance += (mode->xres - var->xres)/2;
+	return distance;
 }
 
 /*
@@ -940,7 +938,7 @@
 	const struct fb_videomode	*db = vesa_modes;
 	int				i, dbsize = 34;
 	int				has_rmx, native_db = 0;
-	int				goodness = 0;
+	int				distance = INT_MAX;
 	const struct fb_videomode	*candidate = NULL;
 
 	/* Start with a copy of the requested mode */
@@ -976,19 +974,19 @@
 	/* Now look for a mode in the database */
 	while (db) {
 		for (i = 0; i < dbsize; i++) {
-			int g;
+			int d;
 
 			if (db[i].yres < src->yres)
 				continue;	
 			if (db[i].xres < src->xres)
 				continue;
-			g = radeon_compare_modes(src, &db[i]);
+			d = radeon_compare_modes(src, &db[i]);
 			/* If the new mode is at least as good as the previous one,
 			 * then it's our new candidate
 			 */
-			if (g >= goodness) {
+			if (d < distance) {
 				candidate = &db[i];
-				goodness = g;
+				distance = d;
 			}
 		}
 		db = NULL;