mdacon incorrectly detects MDA hardware on systems without such graphics card.
one may load this module by chance, for example when doing some systematical
module-testing, and if there is no Monochrome Display Adapter attached , module init
renders vc1-16 completely unusable.
me and others have run into this more than once. see [Bug 224522 - modprobe mdacon
freezes machine -> https://bugzilla.novell.com/show_bug.cgi?id=224522 ] for example
apparently, proper MDA detection seems to be broken for a long time - seems to be
related to those #ifdef TEST_MDA_B statements added by Edward Betts.
this commit back in 2002 made things even worse :
http://git.kernel.org/?p=linux/kernel/git/tglx/history.git;a=commit;h=c72757b49c889144...
it changed default vc allocation from 13-16 to 1-16 for no apparent reason (!?) , and
with that (and without X), mdacon grabs the vc you`re currently sitting on and locks you out.
this is from Kconfig :
As we can see mdacon is just meant as an additional driver for dual-head setup,
and since kernel 2.4.36 still defaults to vc13-16 , setting the default back to that value
again shouldn`t do any harm.
hereby i`m reverting that change, setting default back to to vc13-16 again.
Besides the fact that mdacon may be rarely or never be used these days and could
perhaps put to trash anyway (pre-dinosaur hardware!), indeed this is not a real solution,
but at least it removes the unfortunate side-effect of messing up the vc you`re working on.
Signed-off-by: Roland Kletzing <devzero@web.de>
--- drivers/video/console/mdacon.c.orig 2008-05-03 15:47:20.000000000 +0200
+++ drivers/video/console/mdacon.c 2008-05-03 15:55:27.000000000 +0200
@@ -71,13 +71,15 @@
/* console information */
-static int mda_first_vc = 1;
+static int mda_first_vc = 13;
static int mda_last_vc = 16;
static struct vc_data *mda_display_fg = NULL;
module_param(mda_first_vc, int, 0);
+MODULE_PARM_DESC(mda_first_vc, "First virtual console. Default: 13");
module_param(mda_last_vc, int, 0);
+MODULE_PARM_DESC(mda_last_vc, "Last virtual console. Default: 16");
/* MDA register values
*/
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