Linux-kernel mailing list archive 1997-48,: Re: IDEDMA problems.

# Re: IDEDMA problems.

C. Scott Ananian (cananian@lcs.mit.edu)
Wed, 3 Dec 1997 09:20:16 -0500 (EST)

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On Wed, 3 Dec 1997, Gabriel Paubert wrote:

> On Wed, 3 Dec 1997, C. Scott Ananian wrote:
>
> > > The 'unable to get irq 255' message is very suspicious -- I suspect that
> > > something is putting -1 into a byte somewhere...

> The problem is that 255 means no interrupt line AFAIR. Bios should
> initialize this field in all PCI headers. Try changing your BIOS settings
> first. And checking the return value of pcibios_read_config_byte is
> essentially useless, since this function is only allowed to return
> success in theory (on my PC it does actually return other error codes).

Reading the source indicates that other return values are indeed possible,
at least in theory. The test could stand to be rewritten as an explicit
test against PCIBIOS_SUCCESSFUL to improve the readability of the source,
but that's a minor quibble.

Again, regardless of my BIOS settings, the kernel behavior is incorrect.
The old triton.c driver did not hang, and if 255 really means 'no
interrupt line', then the correct action is certainly not to attempt to
allocate this interrupt.
--Scott
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