Steven Stallion wrote:
> Garrett D'Amore wrote:
>> Steven Stallion wrote:
>>> All,
>>>
>>> Quick question about the various adv_ and en_ properties supported
>>> by dladm:
>>>
>>> >From what I understand, the adv_ properties are to be set by the
>>> driver
>>> (i.e. read-only) for the configurations it supports.
>>>
>>> What purpose do the en_ properties serve? Are these properties a way of
>>> allowing the user to specify a subset of configurations a driver may
>>> use
>>> to select the best configuration available?
>>>
>>> Why would this be desired over setting the duplex and speed properties
>>> instead?
>>>
>>
>> en_xxx set the bits used in 802.3u (MII) configuration. Directly
>> setting the duplex and speed properties would be a subset of
>> functionality. (Because using the en_xxx bits, you can offer to
>> support more than a single configuration ... e.g. you could offer to
>> support 100 FDX *and* 10 FDX.)
>
> Okay, so lets say that en_10fdx_cap and en_100hdx_cap are set; does
> this affect negotiation? Is there a heuristic for choosing the correct
> cap?
Yes. 802.3 defines a preference ordering... 100fdx selected first, then
100hdx, then 10fdx, then 10hdx. I can't recall where 100T4 fits in, but
I've yet to see a device that supports 100T4 and any of the others, so
its kind of irrelevant. (ISTR that 100T4 got priority over the other
100base-T modes because the designers were concerned that 100T4 might be
*necessary* to operate over Category 3 cable.)
-- Garrett
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