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Subject[tip:x86/setup] x86, setup: Don't skip mode setting for the standard VGA modes
Commit-ID:  8e92dc767abb58357e696a48fc3d8ce615a9c01a
Gitweb: http://git.kernel.org/tip/8e92dc767abb58357e696a48fc3d8ce615a9c01a
Author: H. Peter Anvin <hpa@zytor.com>
AuthorDate: Fri, 19 Feb 2010 13:21:38 -0800
Committer: H. Peter Anvin <hpa@zytor.com>
CommitDate: Fri, 19 Feb 2010 13:21:38 -0800

x86, setup: Don't skip mode setting for the standard VGA modes

The code for setting standard VGA modes probes for the current mode,
and skips the mode setting if the mode is 3 (color text 80x25) or 7
(mono text 80x25). Unfortunately, there are BIOSes, including the
VMware BIOS, which report the previous mode if function 0F is queried
while the screen is in a VESA mode, and of course, nothing can help a
mode poked directly into the hardware.

As such, the safe option is to set the mode anyway, and only query to
see if we should be using mode 7 rather than mode 3. People who don't
want any mode setting at all should probably use vga=0x0f04
(VIDEO_CURRENT_MODE). It's possible that should be the kernel
default.

Reported-by Rene Arends <R.R.Arends@hro.nl>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <tip-*@git.kernel.org>
---
arch/x86/boot/video-vga.c | 9 +--------
1 files changed, 1 insertions(+), 8 deletions(-)

diff --git a/arch/x86/boot/video-vga.c b/arch/x86/boot/video-vga.c
index 819caa1..ed7aeff 100644
--- a/arch/x86/boot/video-vga.c
+++ b/arch/x86/boot/video-vga.c
@@ -42,22 +42,15 @@ static u8 vga_set_basic_mode(void)
{
struct biosregs ireg, oreg;
u16 ax;
- u8 rows;
u8 mode;

initregs(&ireg);

+ /* Query current mode */
ax = 0x0f00;
intcall(0x10, &ireg, &oreg);
mode = oreg.al;

- set_fs(0);
- rows = rdfs8(0x484); /* rows minus one */
-
- if ((oreg.ax == 0x5003 || oreg.ax == 0x5007) &&
- (rows == 0 || rows == 24))
- return mode;
-
if (mode != 3 && mode != 7)
mode = 3;


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