Re: [PATCH v2 1/2] net: macb: Clean up macb_validate

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Sean Anderson <sean.anderson@seco.com>
Cc: Antoine Tenart <atenart@kernel.org>,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	netdev@vger.kernel.org,
	Nicolas Ferre <nicolas.ferre@microchip.com>,
	Claudiu Beznea <claudiu.beznea@microchip.com>
Subject: Re: [PATCH v2 1/2] net: macb: Clean up macb_validate
Date: Mon, 25 Oct 2021 11:35:04 +0100	[thread overview]
Message-ID: <YXaIWFB8Kx9rm/j9@shell.armlinux.org.uk> (raw)
In-Reply-To: <24d336d7-9c6f-55bc-34dd-ddd796ef8234@seco.com>

On Fri, Oct 22, 2021 at 01:37:34PM -0400, Sean Anderson wrote:
> Hi Russell,
> 
> For "net: phy: add phy_interface_t bitmap support", phylink_or would be
> nice as well. I use it when implementing NA support for PCSs.

I think you actually mean phy_interface_or(). Given that we will need
MAC drivers to provide the union of their PCS support, I think that
would be a sensible addition. Thanks.

> For "net: sfp: augment SFP parsing with phy_interface_t bitmap",
> drivers/net/phy/marvell.c also needs to be converted. This is due to
> b697d9d38a5a ("net: phy: marvell: add SFP support for 88E1510") being
> added to net-next/master.
> 
> (I think you have fixed this in your latest revision)

I haven't - but when I move the patch series onto net-next, that will
need to be updated.

> "net: phylink: use supported_interfaces for phylink validation" looks
> good. Though the documentation should be updated. Perhaps something
> like

Yes, I haven't bothered with the doc updates yet... they will need to
be done before the patches are ready. Thanks for the suggestions though.

> I think "net: macb: populate supported_interfaces member" is wrong.
> Gigabit modes should be predicated on GIGABIT_MODE_AVAILABLE.

It is a conversion of what macb_validate() does - if the conversion is
incorrect, then macb_validate() is incorrect.

If MACB_CAPS_GIGABIT_MODE_AVAILABLE isn't set, but MACB_CAPS_HIGH_SPEED
and MACB_CAPS_PCS are both set, macb_validate() will not zero the
supported mask if e.g. PHY_INTERFACE_MODE_10GBASER is requested - it
will indicate 10baseT and 100baseT speeds are supported. So the current
macb_validate() code basically tells phylink that
PHY_INTERFACE_MODE_10GBASER supports 10baseT and 100baseT speeds! 

This probably is not what is intended, but this is what the code does,
and I'm maintaining bug-compatibility with the current macb_validate()
implementation. Any changes to the behaviour should be a separate
patch - either fixing it before this patch, or fixing it afterwards.
As the series is currently based on v5.14, it may be that this has
already been fixed.

-- 
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