Re: Permissions denied when enabling DMA
On Fri, Aug 01, 2003 at 11:00:56PM +0200, Wayne Gemmell wrote:
> running hdparm /dev/hdc yields
> using_dma = 0 (off)
The kernel didn't enable DMA on the interface the drive is connected to.
> while running hdparm -i /dev/hdc yields
> DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2
Not relevant... you care about the NEXT line, the one that reports
available UDMA modes.
> and hdparm -I /dev/hdc outputs
> DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
The BIOS put the drive into UDMA5 (ATA100), which the drive supports.
> Now when I run hdparm -d1 /dev/hdc I get
> /dev/hdc:
> setting using_dma to 1 (on)
> HDIO_SET_DMA failed: Operation not permitted
> using_dma = 0 (off)
The kernel you're using doesn't have support for your IDE chipset. This
is why the kernel didn't enable DMA on its own.
Using hdparm to force DMA is a bad, bad, BAD idea. The kernel usually has
very good reasons for not enabling it.
--
Marc Wilson | You are only young once, but you can stay immature
msw@cox.net | indefinitely.
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