Re: [PATCH v4 net-next 2/8] net: phylink: introduce generic method to query PHY in-band autoneg capability

[Vladimir Oltean <vladimir.oltean@nxp.com>]

On Fri, Nov 18, 2022 at 10:11:06AM -0500, Sean Anderson wrote:
> > +enum phy_an_inband {
> > +	PHY_AN_INBAND_UNKNOWN		= BIT(0),
> 
> Shouldn't this be something like
> 
> 	PHY_AN_INBAND_UNKNOWN		= 0,
> 
> ?

Could be 0 as well. The code explicitly tests against PHY_AN_INBAND_UNKNOWN
everywhere, so the precise value doesn't matter too much.

> What does it mean if a phy returns e.g. 0b101?

You mean PHY_AN_INBAND_ON | PHY_AN_INBAND_UNKNOWN. Well, it doesn't mean
anything, it's not a valid return code. I didn't make the code too defensive
in this regard, because I didn't see a reason for making some pieces of
code defend themselves against other pieces of code. It's a bit mask of
3 bits where not all combinations are valid. Even if PHY_AN_INBAND_UNKNOWN
was defined as 0 instead of BIT(0), it would still be just as logically
invalid to return PHY_AN_INBAND_ON | PHY_AN_INBAND_UNKNOWN, but this
would be indistinguishable in machine code from just PHY_AN_INBAND_ON.

I don't know, I don't see a practical reason to make a change here.