linux-kernel - Re: [net-next RFC PATCH v2 2/3] net: phy: Add support for Aeonsemi AS21xxx PHYs

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Message-ID: <67e444e6.050a0220.81044.004e@mx.google.com>
Date: Wed, 26 Mar 2025 19:18:12 +0100
From: Christian Marangi <ansuelsmth@...il.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next RFC PATCH v2 2/3] net: phy: Add support for Aeonsemi
 AS21xxx PHYs

On Wed, Mar 26, 2025 at 06:08:09PM +0000, Russell King (Oracle) wrote:
> On Wed, Mar 26, 2025 at 03:56:15PM +0100, Andrew Lunn wrote:
> > After the firmware download, the phylib core will still have the wrong
> > ID values. So you cannot use PHY_ID_MATCH_EXACT(PHY_ID_AS21011JB1).
> > But what you can do is have a .match_phy_device function. It will get
> > called, and it can read the real ID from the device, and perform a
> > match. If it does not match return -ENODEV, and the core will try the
> > next entry.
> 
> Before it returns -ENODEV, it could re-read the ID values and fill
> them into struct phy_device. This would allow phylib's matching to
> work.
>

Is it ok for PHY driver to change values in phy_device ""externally"" to
phy_device.c ? Maybe you still have to read the other response but a
bool with needs_rescan to handle this internally? 

> > You either need N match_phy_device functions, one per ID value, or you
> > can make use of the .driver_data in phy_driver, and place the matching
> > data there.
> 
> An alternative would be to change the match_phy_device() method to
> pass the phy_driver, which would allow a single match_phy_device
> function to match the new hardware ID values against the PHY IDs in
> the phy_driver without needing to modify the IDs in phy_device.
> 

I also considered extending the function with additional stuff but then
I considered that would mean rework each PHY driver and destroy PHY
driver downstream, not something we should care but still quite a big
task. If the -ENODEV path is not OK, I feel an additional OP is better
than tweaking match_phy_device.

-- 
	Ansuel