From 1514ab09edb071345fe17cd230c97f9e72c9478e Mon Sep 17 00:00:00 2001 From: Mikael Pettersson Date: Tue, 24 Jul 2007 00:25:59 +0200 Subject: [x86 setup] APM detection logic bug fix Starting with kernel 2.6.23-rc1, the i386 APM driver fails on several of my machines with the message: apm: BIOS not found This happens because of a bug in the i386 boot code rewrite from assembler to C. The original assembly code had the following code in its APM BIOS presence test (boot/setup.S): andw $0x02, %cx # Is 32 bit supported? je done_apm_bios # No 32-bit, no (good) APM BIOS That is, the code bails out if bit 2 is zero. In the new C version, this is coded as (boot/apm.c): if (cx & 0x02) /* 32 bits supported? */ return -1; Here we see that the test has been accidentally inverted. The fix is to negate the test. I've verified that this allows the APM driver to work again on my affected machines. Signed-off-by: Mikael Pettersson Signed-off-by: H. Peter Anvin --- arch/i386/boot/apm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/i386/boot/apm.c b/arch/i386/boot/apm.c index a34087c370c..8be3f5686af 100644 --- a/arch/i386/boot/apm.c +++ b/arch/i386/boot/apm.c @@ -40,7 +40,7 @@ int query_apm_bios(void) if (bx != 0x504d) /* "PM" signature */ return -1; - if (cx & 0x02) /* 32 bits supported? */ + if (!(cx & 0x02)) /* 32 bits supported? */ return -1; /* Disconnect first, just in case */ -- cgit v1.2.3