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Date:   Thu, 07 Jan 2021 10:56:10 +0100
From:   Michael Walle <michael@walle.cc>
To:     Saravana Kannan <saravanak@google.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>, kernel-team@android.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] driver core: Fix device link device name collision
In-Reply-To: <20210106232641.459081-1-saravanak@google.com>
References: <20210106232641.459081-1-saravanak@google.com>
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Hi Saravana,

Am 2021-01-07 00:26, schrieb Saravana Kannan:
> The device link device's name was of the form:
> <supplier-dev-name>--<consumer-dev-name>
> 
> This can cause name collision as reported here [1] as device names are
> not globally unique. Since device names have to be unique within the
> bus/class, add the bus/class name as a prefix to the device names used 
> to
> construct the device link device name.
> 
> So the devuce link device's name will be of the form:
> <supplier-bus-name>:<supplier-dev-name>--<consumer-bus-name><consumer-dev-name>
> 
> [1] - 
> https://lore.kernel.org/lkml/20201229033440.32142-1-michael@walle.cc/
> Reported-by: Michael Walle <michael@walle.cc>
> Signed-off-by: Saravana Kannan <saravanak@google.com>

missing Fixes: tag?

> Can you please test this? This should fix your issue.

Unfortunately, not:

[    4.234617] fsl_enetc 0000:00:00.0: Adding to iommu group 1
[    4.346768] fsl_enetc 0000:00:00.0: enabling device (0400 -> 0402)
[    4.353012] fsl_enetc 0000:00:00.0: no MAC address specified for SI1, 
using 3e:6a:a1:57:9c:b0
[    4.361580] fsl_enetc 0000:00:00.0: no MAC address specified for SI2, 
using 9e:8b:7b:e3:e2:ad
[    4.370539] libphy: Freescale ENETC MDIO Bus: probed
[    4.376751] libphy: Freescale ENETC internal MDIO Bus: probed
[    4.383060] fsl_enetc 0000:00:00.1: Adding to iommu group 2
[    4.494764] fsl_enetc 0000:00:00.1: enabling device (0400 -> 0402)
[    4.501012] fsl_enetc 0000:00:00.1: no MAC address specified for SI1, 
using ee:99:cb:b1:24:4c
[    4.509580] fsl_enetc 0000:00:00.1: no MAC address specified for SI2, 
using 66:60:f4:0d:9e:e0
[    4.518556] sysfs: cannot create duplicate filename 
'/devices/platform/soc/1f0000000.pcie/pci0000:00/0000:00:00.1/consumer:0000:00:00.1'
[    4.530882] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 
5.11.0-rc2-next-20210107-00017-g392ec8cbdef5 #303
[    4.540317] Hardware name: Kontron KBox A-230-LS (DT)
[    4.545385] Call trace:
[    4.547834]  dump_backtrace+0x0/0x1b8
[    4.551517]  show_stack+0x20/0x70
[    4.554844]  dump_stack+0xd8/0x134
[    4.558258]  sysfs_warn_dup+0x6c/0x88
[    4.561932]  sysfs_do_create_link_sd.isra.2+0x10c/0x110
[    4.567175]  sysfs_create_link+0x2c/0x50
[    4.571109]  devlink_add_symlinks+0x110/0x1b8
[    4.575484]  device_add+0x460/0x798
[    4.578982]  device_link_add+0x46c/0x628
[    4.582917]  fw_devlink_create_devlink+0xb8/0xc8
[    4.587549]  __fw_devlink_link_to_suppliers+0x84/0x180
[    4.592705]  __fw_devlink_link_to_suppliers+0x134/0x180
[    4.597948]  device_add+0x778/0x798
[    4.601445]  device_register+0x28/0x38
[    4.605205]  __mdiobus_register+0x94/0x340
[    4.609317]  of_mdiobus_register+0xb4/0x380
[    4.613513]  enetc_pf_probe+0x73c/0xb10
[    4.617362]  local_pci_probe+0x48/0xb8
[    4.621125]  pci_device_probe+0x120/0x1c0
[    4.625146]  really_probe+0xec/0x3c0
[    4.628732]  driver_probe_device+0x60/0xc0
[    4.632842]  device_driver_attach+0x7c/0x88
[    4.637039]  __driver_attach+0x60/0xe8
[    4.640799]  bus_for_each_dev+0x7c/0xd0
[    4.644647]  driver_attach+0x2c/0x38
[    4.648232]  bus_add_driver+0x194/0x1f8
[    4.652079]  driver_register+0x6c/0x128
[    4.655927]  __pci_register_driver+0x4c/0x58
[    4.660213]  enetc_pf_driver_init+0x2c/0x38
[    4.664412]  do_one_initcall+0x54/0x2d8
[    4.668260]  kernel_init_freeable+0x200/0x26c
[    4.672631]  kernel_init+0x1c/0x120
[    4.676131]  ret_from_fork+0x10/0x30
[    4.679758] libphy: Freescale ENETC MDIO Bus: probed
[    4.686590] fsl_enetc 0000:00:00.2: Adding to iommu group 3
[    4.798764] fsl_enetc 0000:00:00.2: enabling device (0400 -> 0402)
[    4.805010] fsl_enetc 0000:00:00.2: no MAC address specified for SI0, 
using 2a:90:8e:f9:ee:5d
[    4.814279] fsl_enetc 0000:00:00.6: Adding to iommu group 4
[    4.819992] fsl_enetc 0000:00:00.6: device is disabled, skipping
[    4.826146] fsl_enetc_mdio 0000:00:00.3: Adding to iommu group 5
[    4.938764] fsl_enetc_mdio 0000:00:00.3: enabling device (0400 -> 
0402)
[    4.945601] libphy: FSL PCIe IE Central MDIO Bus: probed

Please note the:
[    4.518556] sysfs: cannot create duplicate filename 
'/devices/platform/soc/1f0000000.pcie/pci0000:00/0000:00:00.1/consumer:0000:00:00.1'

Your patch just addresses the link names, but not the ones for 
"consumer:"
and "supplier:" under the device itself, right?

> Having said that, do you have some local DT changes when you are 
> testing
> this?

No. But keep in mind that this is also PCI and there might be other
devices too.

> Because it's not obvious from the DT in upstream what dependency
> is even being derived from the firmware. I don't see any dependency in
> upstream DT files between mdio_bus/0000:00:00.1 and
> pci0000:00/0000:00:00.1

I guess that would be this:
https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/freescale/enetc/enetc_pf.c#L748

which registers an mdio bus on the same PCI device as the ENETC.

-michael