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

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Message-ID: <090efb05-eb2b-4412-aa85-16df05ac9fb5@quicinc.com>
Date: Thu, 29 May 2025 15:16:51 -0700
From: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>
To: Paolo Abeni <pabeni@...hat.com>, Quentin Schulz <foss+kernel@...il.net>,
        Andrew Lunn <andrew+netdev@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Maxime
 Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue
	<alexandre.torgue@...s.st.com>
CC: 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] net: stmmac: platform: guarantee uniqueness of bus_id



On 5/26/2025 1:26 PM, Paolo Abeni wrote:
> On 5/21/25 5:21 PM, Quentin Schulz 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.
>>
>> Signed-off-by: Quentin Schulz <quentin.schulz@...rry.de>
> 
> I think no need to CC stable here, but you need to provide a suitable
> fixes tag, thanks!
> 
Quentin to make your life easy. 
It fixes this patch 
https://lore.kernel.org/lkml/1372930541-19409-1-git-send-email-srinivas.kandagatla@st.com/
dt:net:stmmac: Add support to dwmac version 3.610 and 3.710
It goes back in time to 2013 when this bus_id was introduced through dts

> Paolo
> 
>