linux-kernel - Re: [PATCH net-next 3/4] net: phy: Add helper to derive the number of ports from a phy mode

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Date:   Thu, 28 Jul 2022 14:44:47 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc:     davem@...emloft.net, Rob Herring <robh+dt@...nel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, thomas.petazzoni@...tlin.com,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org, Horatiu.Vultur@...rochip.com,
        Allan.Nielsen@...rochip.com, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net-next 3/4] net: phy: Add helper to derive the number of
 ports from a phy mode

On 7/28/22 14:32, Andrew Lunn wrote:
>> +int phy_interface_num_ports(phy_interface_t interface)
>> +{
>> +	switch (interface) {
>> +	case PHY_INTERFACE_MODE_NA:
>> +	case PHY_INTERFACE_MODE_INTERNAL:
>> +		return 0;
> 
> I've not yet looked at how this is used. Returning 0 could have
> interesting effects i guess? INTERNAL clearly does have some sort of
> path between the MAC and the PHY, so i think 1 would be a better
> value. NA is less clear, it generally means Don't touch. But again,
> there still needs to be a path between the MAC and PHY, otherwise
> there would not be any to touch.
> 
> Why did you pick 0?

I would agree that returning 1 is a more sensible default to avoid breaking users of that function. However this makes me wonder, in what case will we break the following common meaning:

- Q -> quad
- P -> penta
- O -> octal

Is the helper really needed in the sense that the phy_interface_t enumeration is explicit enough thanks to or because of its name?
--
Florian