linux-kernel - [PATCH] fbdev: make the best-fit section of fb_find

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Message-ID: <20080127113115.GA17722@spock.one.pl>
Date:	Sun, 27 Jan 2008 12:31:16 +0100
From:	Michal Januszewski <spock@...too.org>
To:	linux-fbdev-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] fbdev: make the best-fit section of fb_find_mode return
	the closest matching mode

From: Michal Januszewski <spock@...too.org>

Currently, if a perfect match in terms of resolution is not found,
fb_find_mode() only looks for a best-fit mode among modes with a
higher resolution than the one requested.  Thus, if the user
requests a resolution higher than the largest supported one, they
are dropped to the default mode (usually a low resolution one).

Change this behaviour so that the true closest match in terms
of the city-block metric is returned.

Signed-off-by: Michal Januszewski <spock@...too.org>
---
diff --git a/drivers/video/modedb.c b/drivers/video/modedb.c
index 08d0725..bc29ef3 100644
--- a/drivers/video/modedb.c
+++ b/drivers/video/modedb.c
@@ -655,15 +655,15 @@ done:
 	best = -1;
 	DPRINTK("Trying best-fit modes\n");
 	for (i = 0; i < dbsize; i++) {
-	    if (xres <= db[i].xres && yres <= db[i].yres) {
 		DPRINTK("Trying %ix%i\n", db[i].xres, db[i].yres);
 		if (!fb_try_mode(var, info, &db[i], bpp)) {
-		    if (diff > (db[i].xres - xres) + (db[i].yres - yres)) {
-			diff = (db[i].xres - xres) + (db[i].yres - yres);
-			best = i;
-		    }
+			if (diff > abs(db[i].xres - xres) +
+				   abs(db[i].yres - yres)) {
+				diff = abs(db[i].xres - xres) +
+				       abs(db[i].yres - yres);
+				best = i;
+			}
 		}
-	    }
 	}
 	if (best != -1) {
 	    fb_try_mode(var, info, &db[best], bpp);

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