VGA console font problems on 2.6 kernel

PATCH New Takashi Iwai 1 participant 1 message Sep 24, 2004

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Framebuffer layer Char and misc drivers Console

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Takashi Iwai

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2004-09-24 13:23 UTC #0 lore raw

PATCH 1/1 VGA console font problems on 2.6 kernel

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 <[email protected]> ALSA Developer - www.alsa-project.org

Quoted 34 lines

Subject: [kernel] VGA Text Console Issues
From: Egbert Eich <[email protected]>
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.

Quoted 5 lines

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.

drivers/char/vt.c renamed from drivers/char/vt.c.orig +4 -0

@@ -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;

drivers/video/console/vgacon.c +3 -1

@@ -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;
 }