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To:     Andre Przywara <andre.przywara@arm.com>, nic_swsd@realtek.com
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Sayanta Pattanayak <sayanta.pattanayak@arm.com>
References: <20210624154945.19177-1-andre.przywara@arm.com>
From:   Heiner Kallweit <hkallweit1@gmail.com>
Subject: Re: [PATCH v2] r8169: Avoid duplicate sysfs entry creation error
Message-ID: <bb2e4938-0a7c-1b02-25f5-5615d3a1b1c7@gmail.com>
Date:   Thu, 24 Jun 2021 20:41:25 +0200
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On 24.06.2021 17:49, Andre Przywara wrote:
> From: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
> 
> When registering the MDIO bus for a r8169 device, we use the PCI B/D/F
> specifier as a (seemingly) unique device identifier.
> However the very same BDF number can be used on another PCI segment,
> which makes the driver fail probing:
> 
> [ 27.544136] r8169 0002:07:00.0: enabling device (0000 -> 0003)
> [ 27.559734] sysfs: cannot create duplicate filename '/class/mdio_bus/r8169-700'
> ....…
> [ 27.684858] libphy: mii_bus r8169-700 failed to register
> [ 27.695602] r8169: probe of 0002:07:00.0 failed with error -22
> 
> Add the segment number to the device name to make it more unique.
> 
> This fixes operation on an ARM N1SDP board, where two boards might be
> connected together to form an SMP system, and all on-board devices show
> up twice, just on different PCI segments.
> 
> Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
> [Andre: expand commit message, use pci_domain_nr()]
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> Now compile-tested on ARM, arm64, ppc64, sparc64, mips64, hppa, x86-64,
> i386.
> 
Good. Patch is missing the net vs. net-next annotation, therefore the
remaining question is whether to treat this as a fix. Seems nobody but
you was affected so far, therefore handling it as an improvement should
be fine as well.

If you need this change on previous kernel versions:
Add net annotation and add a Fixes tag (I think when driver was switched
to phylib with 4.19). Else add a net-next annotation.

See the following link for details:
https://www.kernel.org/doc/Documentation/networking/netdev-FAQ.txt

> Changes v1 ... v2:
> - use pci_domain_nr() wrapper to fix compilation on various arches
> 
>  drivers/net/ethernet/realtek/r8169_main.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 2c89cde7da1e..5f7f0db7c502 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -5086,7 +5086,8 @@ static int r8169_mdio_register(struct rtl8169_private *tp)
>  	new_bus->priv = tp;
>  	new_bus->parent = &pdev->dev;
>  	new_bus->irq[0] = PHY_MAC_INTERRUPT;
> -	snprintf(new_bus->id, MII_BUS_ID_SIZE, "r8169-%x", pci_dev_id(pdev));
> +	snprintf(new_bus->id, MII_BUS_ID_SIZE, "r8169-%x-%x",
> +		 pci_domain_nr(pdev->bus), pci_dev_id(pdev));
>  
>  	new_bus->read = r8169_mdio_read_reg;
>  	new_bus->write = r8169_mdio_write_reg;
>