New-bus unit wiring via hints..

[Marcel Moolenaar]

On Oct 11, 2007, at 9:01 PM, Peter Wemm wrote:

> On Thursday 11 October 2007, Marcel Moolenaar wrote:
>> On Oct 11, 2007, at 2:41 PM, John Baldwin wrote:
>>> 2) One of the things this fixes that is visible to users is that if
>>> your
>>>    machine gets the COM ports backwards when using ACPI it should
>>> now get
>>>    them correct (COM1 as sio0) assuming your COM ports use the
>>> default hints
>>>    and you have the default sio hints in your /boot/device.hints
>>> file.
>>
>> I think you just pointed out the problem of using hints to wire
>> down unit numbers, because hints will stop hinting and will start
>> dictating. If I swap the serial ports in the BIOS then surely
>> my hints will be wrong and ACPI will be right.
>
> Not necessarily.  It has been a long standing problem that ACPI is  
> wrong
> (or sub-optimal) about serial ports.  There are many machines that  
> list
> 0x2f8 first, and 0x3f8 second.  As a result, we bind sio0 to com2, and
> sio1 to com1.

I don't think it's wrong. It's just non-legacy. The whiole purpose
of ACPI is to migrate away from those legacy resource allocations
and allow for greater flexibility. It seems to me that instead of
embracing the freedom for BIOS/firmware writers, we hold on to those
old and obsolete notions. As such, it's not a step forwards, it's
a step back.

> I like the way John did it.  It reserves the unit numbers for hardware
> that matches the hints.

This is not a bad thing, but the ambiguity introduced by re-using
hints for that is bad and a recipe for problems.

-- 
Marcel Moolenaar
xcllnt at mac.com