Date: Sun, 25 Jul 1999 00:41:52 +0100 (BST) From: Andrew Gordon <arg@arg1.demon.co.uk> To: hackers@freebsd.org Subject: Linear buffers in VESA screen modes Message-ID: <Pine.BSF.3.96.990725002543.6533B-100000@server.arg.sj.co.uk>
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Is there a plan for how to access the linear framebuffer in VESA video
modes? So far as I can tell, the current[1] VESA code doesn't support
enabling the linear framebuffer access at all, even though "vidcontrol -i
mode" is happy to tell you the details of the buffers that you can't get
access to!
[1] actually, I'm working in -stable, but at a quick glance the -current
code is the same in this area.
I have used the following hack to make it work for my purposes:
% cvs diff -c vesa.c
Index: vesa.c
===================================================================
RCS file: /repository/src/sys/i386/isa/vesa.c,v
retrieving revision 1.15.2.5
diff -c -r1.15.2.5 vesa.c
*** vesa.c 1999/04/16 15:58:21 1.15.2.5
--- vesa.c 1999/07/24 23:26:21
***************
*** 777,783 ****
}
#endif /* 0 */
! if (vesa_bios_set_mode(mode))
return 1;
#if VESA_DEBUG > 0
--- 777,784 ----
}
#endif /* 0 */
! /* If mode has a linear buffer, enable use of it */
! if (vesa_bios_set_mode(info.vi_buffer ? (mode | 0x4000) : mode))
return 1;
#if VESA_DEBUG > 0
This currently does the right thing (at least on my hardware) because all
the modes that syscons supports for character I/O don't have a linear
mapping and hence those modes get set for windowed access as before.
However, it's probably not the proper solution.
The application for which I need this is to support capture from the bktr
driver onto the screen (ie. so that you can watch TV without X). With the
above hack and a small (100-line) program it works very nicely - far
tidier than installing X just for this purpose on some embedded systems
where I need this capability.
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