netdev - RE: [PATCH v4 net-next 04/10] net/ncsi: Ethtool operation to get NCSI topology

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Date:   Mon, 8 May 2017 12:40:28 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Gavin Shan' <gwshan@...ux.vnet.ibm.com>
CC:     Stephen Hemminger <stephen@...workplumber.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "joe@...ches.com" <joe@...ches.com>,
        "kubakici@...pl" <kubakici@...pl>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [PATCH v4 net-next 04/10] net/ncsi: Ethtool operation to get
 NCSI topology

From: Gavin Shan
> Sent: 08 May 2017 01:20
...
> >Why 16 bits?
> >You are just making life hard for the compiler and possibly generating
> >random padding.
> >
> 
> It's because there are 256 NCSI channels to maximal degree. So 16-bits
> is the minial data width to hold it in signed format. Yes, I think
> __s32 would be better in this case. However, I would like to discard
> the negotiation mechanism in next respin.

Just because the domain of a value fits in 16 bits doesn't mean
that a 16bit type is appropriate.

It is generally much better to use 32 (aka machine word) sized
items unless you have an array or are trying to fit a lot of
items into a small memory area.

	David