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To: Hans Petter Selasky <hps@selasky.org>
From: Mike Karels <mike@karels.net>
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Subject: Re: Adding new media types to if_media.h
In-reply-to: Your message of Thu, 26 Feb 2015 10:39:02 +0100.
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Date: Thu, 26 Feb 2015 08:21:41 -0600
Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>,
 Eric Joyner <ricera10@gmail.com>, Gleb Smirnoff <glebius@FreeBSD.org>,
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> I'm doing some work for Mellanox and we need some 100GBase types for 
> coming hardware products too.

> I think we are not using the 32-bits of "ifm_media" well enough.

> Has it been discussed to add more bits to "IFM_NMASK" and have more 
> ethernet types like IFM_ETHER_0, IFM_ETHER_1, IFM_ETHER_2, IFM_ETHER_3 ....

> Currently 5 IFM types are defined. If 2 more bits can be added to 
> IFM_NMASK we have 5 bits total giving us 2**5 = 32 IFM types. Then it 
> should be possible to define "(32 - 5) * 32 = 864" more ethernet types, 
> which I think should be enough for now - or we add even one more bit to 
> IFM_NMASK ?

Did you have specific bits in mind?  I'm fairly sure they are all assigned
to something now.  The adjacent bits are used for the subtype/variant and
options.  Most of the options are used, maybe not all.

I haven't checked whether the "instance" field is still used, though.  It
was for MII PHY numbers, I believe.

If we had more bits, it seems better to put them directly into the subtype
field rather than the type field.

		Mike