linux-kernel - Re: [PATCH net v2] net: stmmac: platform: guarantee uniqueness of bus

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Message-ID: <20250527145659.00bd10ae@device-24.home>
Date: Tue, 27 May 2025 14:56:59 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Quentin Schulz <foss+kernel@...il.net>
Cc: 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>, Maxime Coquelin
 <mcoquelin.stm32@...il.com>, Alexandre Torgue
 <alexandre.torgue@...s.st.com>, Jakob Unterwurzacher
 <jakob.unterwurzacher@...rry.de>, Heiko Stuebner <heiko@...ech.de>,
 netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Quentin
 Schulz <quentin.schulz@...rry.de>
Subject: Re: [PATCH net v2] net: stmmac: platform: guarantee uniqueness of
 bus_id

Hello Quentin,

On Tue, 27 May 2025 13:56:23 +0200
Quentin Schulz <foss+kernel@...il.net> wrote:

> From: Quentin Schulz <quentin.schulz@...rry.de>
> 
> bus_id is currently derived from the ethernetX alias. If one is missing
> for the device, 0 is used. If ethernet0 points to another stmmac device
> or if there are 2+ stmmac devices without an ethernet alias, then bus_id
> will be 0 for all of those.
> 
> This is an issue because the bus_id is used to generate the mdio bus id
> (new_bus->id in drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
> stmmac_mdio_register) and this needs to be unique.
> 
> This allows to avoid needing to define ethernet aliases for devices with
> multiple stmmac controllers (such as the Rockchip RK3588) for multiple
> stmmac devices to probe properly.
> 
> Obviously, the bus_id isn't guaranteed to be stable across reboots if no
> alias is set for the device but that is easily fixed by simply adding an
> alias if this is desired.
> 
> Fixes: 25c83b5c2e82 ("dt:net:stmmac: Add support to dwmac version 3.610 and 3.710")
> Signed-off-by: Quentin Schulz <quentin.schulz@...rry.de>

This looks correct, thanks !

Reviewed-by: Maxime Chevallier <maxime.chevallier@...tlin.com>

Maxime