[PATCH] VGA console font problems on 2.6 kernel

[Takashi Iwai <tiwai@suse.de>]

Hi,

Egbert Eich of Xorg reported the problems of VGA console on 2.6
kernels.  I forward his original post and proposed patches here to
LKML, since this should be discussed / audited better here.

The patch below can be applied to 2.6.9-rc2.


Any comments, please?

Thanks.

--
Takashi Iwai <tiwai@suse.de>		ALSA Developer - www.alsa-project.org


> Subject: [kernel] VGA Text Console Issues
> From: Egbert Eich <eich@suse.de>
> 
> I would like to utilize kernel ioctls to save/restore console fonts 
> in VGA text mode when running X. So far the Xserver takes care of this
> however there more and more problems with this:
>         1. On some platforms (IA64) we need to POST the BIOS before
> 	   we even have a chance to access the hardware ourselves.
> 	   This POSTing will usually undo any changes to the graphics
> 	   hardware that the kernel may have done.
> 	2. More and more drivers fully rely on BIOS support however
> 	   the BIOS functions which could be used to save/restore 
> 	   register settings may be broken so the only way of mode
> 	   save/restore is getting/setting the BIOS mode ID.
> 
> I've hacked up some code for X however I ran into two problems:
> 
> 1. con_font_get() in linux/drivers/char/vt.c seems to be broken as
>    the font parameters (height, width, charcount) are never reported
>    back. Therefore this function seems to be pretty useless.
>    The fix is simple (please see below).
> 
> 2. fb consoles seem to allow to install fonts per vt so that the user
>    can have a different font on every console. The text console driver
>    doesn't support this: the font is downloaded to the video card 
>    and will be used for all systems. Still the vga_con driver stores
>    the font parameters per console with the effect that setting a 
>    font with different parameters on one console will result in the
>    wron values when this font information is read back from another
>    console.
>    Appearantly this broken feature has been introduced in 2.6 as 
>    in the 2.4 kernel the vga_con font information is stored in one
>    single global variable.
> 
> The IA64 platform at least still heavily relies on the VGA text console.
> To be able to fix some VT switching issues with X on this platform I
> need these two issues resolved.
> 
> Egbert.


--- linux/drivers/char/vt.c.orig	2004-09-22 07:12:15.000000000 -0700
+++ linux/drivers/char/vt.c	2004-09-23 07:39:50.206885656 -0700
@@ -3079,6 +3079,10 @@
 	if (rc)
 		goto out;
 
+	op->height = font.height;
+	op->width = font.width;
+	op->charcount = font.charcount;
+
 	if (op->data && copy_to_user(op->data, font.data, c))
 		rc = -EFAULT;
 
--- linux/drivers/video/console/vgacon.c	2004-09-23 16:54:02.096337495 +0200
+++ linux/drivers/video/console/vgacon.c	2004-09-23 16:57:32.149761950 +0200
@@ -901,8 +901,10 @@ static int vgacon_adjust_height(struct v
 	for (i = 0; i < MAX_NR_CONSOLES; i++) {
 		struct vc_data *c = vc_cons[i].d;
 
-		if (c && c->vc_sw == &vga_con)
+		if (c && c->vc_sw == &vga_con) {
+			c->vc_font.height = fontheight;
 			vc_resize(c->vc_num, 0, rows);	/* Adjust console size */
+		}
 	}
 	return 0;
 }