netdev - Re: [PATCH net-next v2 2/4] net: dsa: ks8955: Delete KSZ8864 and KSZ8795 support

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Message-ID: <20260119215818.qiaqdudcz32nk7f2@skbuf>
Date: Mon, 19 Jan 2026 23:58:18 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Linus Walleij <linusw@...nel.org>
Cc: Andrew Lunn <andrew@...n.ch>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Woojung Huh <woojung.huh@...rochip.com>,
	UNGLinuxDriver@...rochip.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/4] net: dsa: ks8955: Delete KSZ8864 and
 KSZ8795 support

On Mon, Jan 19, 2026 at 03:30:06PM +0100, Linus Walleij wrote:
> After studying the datasheets for a bit, I can conclude that
> the register maps for the two KSZ variants explicitly said to
> be supported by this driver are fully supported by the newer
> Micrel KSZ driver, including full VLAN support and a different
> custom tag than what the KS8995 is using.
> 
> Delete this support, users should be using the KSZ driver
> CONFIG_NET_DSA_MICROCHIP_KSZ_SPI and any new device trees should
> use:
> micrel,ksz8864 -> microchip,ksz8864
> micrel,ksz8795 -> microchip,ksz8795

So the binding changes you've done to Documentation/devicetree/bindings/net/micrel-ks8995.txt
in commit a0f29a07b654 ("dt-bindings: dsa: Rewrite Micrel KS8995 in schema")
were apparently backwards-compatible. But this isn't - you're offering
no forward path for existing device trees.

IMO, even if nobody cares about these compatible strings (given that the
"PHY" driver dates from 2016 and the KSZ DSA driver has supported these
chips since 2019), IMO it's pretty hard to sell a loss of hardware support
in a patch set targeted to 'net'.

Does it make more sense to retarget the patches to 'net-next', drop
the Fixes: tags and to somehow mark the driver as "experimental", to set
the expectations about the fact that it's still under development and
many things aren't how they should be?

> 
> Apparently Microchip acquired Micrel at some point and this
> created the confusion.
> 
> Fixes: a7fe8b266f65 ("net: dsa: ks8995: Add basic switch set-up")
> Reported-by: Vladimir Oltean <olteanv@...il.com>
> Signed-off-by: Linus Walleij <linusw@...nel.org>
> ---
>  drivers/net/dsa/ks8995.c | 160 +++++++++--------------------------------------
>  1 file changed, 28 insertions(+), 132 deletions(-)