[PATCH 2.6.24-rc1] sata_promise: fix endianess bug in ASIC PRD bug workaround

[PATCH 2.6.24-rc1] sata_promise: fix endianess bug in ASIC PRD bug workaround

[Mikael Pettersson]

The original workaround for the Promise ASIC PRD bug
contained an endianess bug which I failed to detect:
the adjustment of the last PRD entry's length field
applied host arithmetic to little-endian data, which
is incorrect on big-endian machines.

We have the length available in host-endian format, so
do the adjustment on host-endian data and then convert
and store it in the PRD entry's little-endian data field.

Thanks to an anonymous reviewer for detecting this bug.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
---
Jeff: please include this fix in any backport(s) of the
ASIC PRD bug workaround.

 drivers/ata/sata_promise.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -rupN linux-2.6.24-rc1/drivers/ata/sata_promise.c linux-2.6.24-rc1.sata_promise-endianess-fix/drivers/ata/sata_promise.c
--- linux-2.6.24-rc1/drivers/ata/sata_promise.c	2007-10-31 11:47:13.000000000 +0100
+++ linux-2.6.24-rc1.sata_promise-endianess-fix/drivers/ata/sata_promise.c	2007-10-31 11:47:25.000000000 +0100
@@ -585,7 +585,7 @@ static void pdc_fill_sg(struct ata_queue
 			VPRINTK("Splitting last PRD.\n");
 
 			addr = le32_to_cpu(ap->prd[idx - 1].addr);
-			ap->prd[idx - 1].flags_len -= cpu_to_le32(SG_COUNT_ASIC_BUG);
+			ap->prd[idx - 1].flags_len = cpu_to_le32(len - SG_COUNT_ASIC_BUG);
 			VPRINTK("PRD[%u] = (0x%X, 0x%X)\n", idx - 1, addr, SG_COUNT_ASIC_BUG);
 
 			addr = addr + len - SG_COUNT_ASIC_BUG;

Re: [PATCH 2.6.24-rc1] sata_promise: fix endianess bug in ASIC PRD bug workaround

[Jeff Garzik]

Mikael Pettersson wrote:
> The original workaround for the Promise ASIC PRD bug
> contained an endianess bug which I failed to detect:
> the adjustment of the last PRD entry's length field
> applied host arithmetic to little-endian data, which
> is incorrect on big-endian machines.
> 
> We have the length available in host-endian format, so
> do the adjustment on host-endian data and then convert
> and store it in the PRD entry's little-endian data field.
> 
> Thanks to an anonymous reviewer for detecting this bug.
> 
> Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
> ---
> Jeff: please include this fix in any backport(s) of the
> ASIC PRD bug workaround.
> 
>  drivers/ata/sata_promise.c |    2 +-
>  1 files changed, 1 insertion(+), 1 deletion(-)
> 
> diff -rupN linux-2.6.24-rc1/drivers/ata/sata_promise.c linux-2.6.24-rc1.sata_promise-endianess-fix/drivers/ata/sata_promise.c
> --- linux-2.6.24-rc1/drivers/ata/sata_promise.c	2007-10-31 11:47:13.000000000 +0100
> +++ linux-2.6.24-rc1.sata_promise-endianess-fix/drivers/ata/sata_promise.c	2007-10-31 11:47:25.000000000 +0100
> @@ -585,7 +585,7 @@ static void pdc_fill_sg(struct ata_queue
>  			VPRINTK("Splitting last PRD.\n");
>  
>  			addr = le32_to_cpu(ap->prd[idx - 1].addr);
> -			ap->prd[idx - 1].flags_len -= cpu_to_le32(SG_COUNT_ASIC_BUG);
> +			ap->prd[idx - 1].flags_len = cpu_to_le32(len - SG_COUNT_ASIC_BUG);
>  			VPRINTK("PRD[%u] = (0x%X, 0x%X)\n", idx - 1, addr, SG_COUNT_ASIC_BUG);
>  
>  			addr = addr + len - SG_COUNT_ASIC_BUG;
> -

applied