ide-scsi: DMA alignment bug fixed

ide-scsi: DMA alignment bug fixed

Post by Terry Kyri » Thu, 11 Nov 2004 14:01:26

It's about time somebody fixed this. ide-scsi no longer reverts to PIO
when the user buffers aren't 512-byte aligned, thanks to this patch.

Patches are available for kernels 2.2.26, 2.4.27 and 2.6.9.

Download them from


1. PROBLEM: "kernel BUG at drivers/scsi/ide-scsi.c:493!"

2. Problem with ide-scsi and DMA

I'm using 2.4.24 on two different machines (laptop, via kt133a and desktop
with nforce2 chipset). Both have IDE cd writers and I use hdc=scsi as boot
parameter. The laptop works fine, but the desktop not:
# modprobe ide-scsi
hdc: attached ide-scsi driver.
hdc: DMA disabled

If I want to enable DMA with hdparm, I get this error:

setting using_dma to 1 (on)
HDIO_SET_DMA failed: Operation not permitted
using_dma = 0 (off)

Only if I remove the ide-scsi module, I can set DMA again, reloading
ide-scsi disables dma.
I also tried echo using_dma:1 > /proc/ide/hdc/settings
It works fine without ide-scsi, but is stuck at 0 with ide-scsi (no
errors in syslog).

All above things (hdparm, ...) work on the other machine, so it seems to
be a problem with the nforce2 ide controller (brand-new Asus A7N8X-X
board) and ide-scsi.
I don't use any GPL-conflicting modules (disabled onboard network and
added a realtek card). Kernel compiler is gcc 3.3.1 from SuSE 9.0.

kind regards
Markus Gaugusch

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5. Fwd: DMA problems in ide-scsi

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12. [PATCH 04/40] ide-scsi: fix Interrupt Reason checking in idescsi_pc_intr()

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