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On Friday 05 September 2008, Andrey Borzenkov wrote: > This is regression but old enough. Apparently I had for whatever reasons > EDD turned off till recently. This is 2.6.27-rc5 just in case. > > In 2006 I fixed ghost devices due to buggy BIOS: > > http://marc.info/?l=linux-kernel&m=114087765422490&w=2 > > Later edd.S has been rewritten in C, and apparently this patch has been > lost: > > {pts/1}% ls /sys/firmware/edd > int13_dev80/ int13_dev84/ int13_dev88/ int13_dev8c/ > int13_dev81/ int13_dev85/ int13_dev89/ int13_dev8d/ > int13_dev82/ int13_dev86/ int13_dev8a/ int13_dev8e/ > int13_dev83/ int13_dev87/ int13_dev8b/ int13_dev8f/ > > But I have just a single disk. This is the same system BTW. > > Unfortunately I do not speak asm language of C; if somebody could provide > equivalent fix for current edd.c, I am more than ready to test it. Was it really that simple? Subject: [PATCH] Fix ghost devices under /sys/firmware/edd From: Andrey Borzenkov <arvidjaar@mail.ru> Some BIOSes do not always set CF on error before return from int13. The patch adds additional check for status being zero (AH == 0). This was fixed for edd.S in http://marc.info/?l=linux-kernel&m=114087765422490&w=2, but lost again when edd.S was rewritten in C. Signed-off-by: Andrey Borzenkov <arvidjaar@mail.ru> --- arch/x86/boot/edd.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/arch/x86/boot/edd.c b/arch/x86/boot/edd.c index d93cbc6..bf4ae6f 100644 --- a/arch/x86/boot/edd.c +++ b/arch/x86/boot/edd.c @@ -32,7 +32,9 @@ static int read_mbr(u8 devno, void *buf) : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx) : : "esi", "edi", "memory"); - return -(u8)ax; /* 0 or -1 */ + /* Some BIOSes do not set carry flag on error but still return + * error in AH. The condition below is expected to catch both */ + return -!!ax; /* 0 or -1 */ } static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)[unhandled content-type:application/pgp-signature] | ||||||||||||
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