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Message-ID: <20080906120720.GB30964@elte.hu>
Date: Sat, 6 Sep 2008 14:07:20 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Andrey Borzenkov <arvidjaar@...mail.ru>
Cc: hpa@...or.com, Andrew Morton <akpm@...ux-foundation.org>,
"Rafael J. Wysocki" <rjw@...k.pl>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Ghost EDD devices in /sys again
* Andrey Borzenkov <arvidjaar@...mail.ru> wrote:
> 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@...l.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@...l.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)
looks good to me - applied it to tip/x86/urgent. Thanks Andrey!
Ingo
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