Re: fbcon has a empty unimap after boot

Hi.

I noticed that with 2.6.0 kernels, when using fbcon
(with the sisfb driver in my case, using a Sis630 card), the
ioctl GIO_UNIMAP returns a empty unimap.
This results in problems for BRLTTY[1], which relies
on a valid unimap to back-translate the font-positions of
/dev/vcsa to the actual characters used.

Further digging showed that this problems has probably gone
unnoticed because there is a special case in
drivers/char/consolemap.c:conv_uni_to_pc which returns -3 when
there is no unimap available.  This -3 return value
is caught in drivers/char/vt.c:do_con_write like this:

                        tc = conv_uni_to_pc(vc_cons[currcons].d, tc);
                        ...
                        } else if ( tc == -3 ) {
                                /* Bad hash table -- hope for the best */
                                tc = c;
                        }

This is why I think the uninitialized unimap did go
unnoticed, since this code will make things work for
standard iso-8859 type of charsets.

However, user space apps which rely on GIO_UNIMAP do not
work correctly, and in general, I think I18N should be broken
on fbcon currently.

I have a very crude patch which works for me here, but I
am not sure if this is the right way to fix this.
Anyway, it is attached.  Note that I am very new to
kernel hacking, so my analysis of the problem might be
bogus, but I do think I am on the right track...

--- linux-2.6.0-test4/drivers/video/console/fbcon.c.orig        2003-09-03 15:32:42.000000000 +0200
+++ linux-2.6.0-test4/drivers/video/console/fbcon.c     2003-09-03 15:27:09.000000000 +0200

@@ -695,6 +695,7 @@
                fb_display[unit].scrollmode = SCROLL_YNOMOVE;
        else
                fb_display[unit].scrollmode = SCROLL_YREDRAW;
+       con_set_default_unimap(unit);
        fbcon_set_display(vc, init, !init);
 }

[1] http://mielke.cc/brltty/