Re: [PATCH] vgacon: Workaround for resize bug in some chipsets

From: Jason Dravet
Date: Wed Nov 16 2005 - 20:36:53 EST

From: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
To: Jason Dravet <dravet@xxxxxxxxxxx>
CC: 7eggert@xxxxxx, adaplas@xxxxxxxxx, torvalds@xxxxxxxx, akpm@xxxxxxxx,davej@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [PATCH] vgacon: Workaround for resize bug in some chipsets
Date: Thu, 17 Nov 2005 00:52:16 +0100


The following patch should correct the issue:

When doublescan mode is in use, scanlines must be doubled.

Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>

--- drivers/video/console/vgacon.c.orig 2005-11-17 00:40:02.000000000 +0100
+++ drivers/video/console/vgacon.c 2005-11-17 00:42:27.000000000 +0100
@@ -502,10 +502,16 @@
unsigned long flags;
unsigned int scanlines = height * c->vc_font.height;
- u8 scanlines_lo, r7, vsync_end, mode;
+ u8 scanlines_lo, r7, vsync_end, mode, max_scan;

spin_lock_irqsave(&vga_lock, flags);

+ outb_p(VGA_CRTC_MAX_SCAN, vga_video_port_reg);
+ max_scan = inb_p(vga_video_port_val);
+ if (max_scan & 0x80)
+ scanlines <<= 1;
outb_p(VGA_CRTC_MODE, vga_video_port_reg);
mode = inb_p(vga_video_port_val);

The patch does fix my problem. Thank you Samuel. I really appreciate the work you and Antonino have done on this issue. I look forward to seeing this patch in the mainline.

Thanks again,
Jason Dravet

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at