Re: More than 10 IDE interfaces

[Martin Dalecki <dalecki@evision-ventures.com>]

Bill Davidsen wrote:
> On Thu, 11 Apr 2002, Martin Dalecki wrote:
> 
> 
>>Baldur Norddahl wrote:
>>
>>>Hi,
>>>
>>>I have a machine with the following configuration:
>>>
>>>2 on board IDE interfaces (AMD chipset)
>>>2 Promise Technology UltraDMA100 controllers with each 2 IDE interfaces.
>>>4 Promise Technology UltraDMA133 controllers with each 2 IDE interfaces.
>>>
>>>This adds up to 14 IDE interfaces. And I just discovered that the kernel
>>>only supports 10 IDE interfaces :-(
>>>
>>>So I tried to hack the kernel, and I was partially successfull. I changed
>>>MAX_HWIF from 10 to 14. I made up some major numbers for the extra
>>
>>In your case if should be changed to 15 there is an off by one error here in the
>>interpretation of this constant.
> 
> 
>   ??? If the current value is 10, and supports 10 interfaces, and I
> believe that is the case, why should he need a value of 15 to get 14?
> Doesn't the off by one error happen on smaller values, or what?
> 
>   I am NOT disagreeing with you, I just don't see how to code an off by
> one and have it work some of the time and not others.

You can have luck due to alignment issues.