linux-kernel - Re: [RESEND PATCH v7 1/1] PCI/sysfs: Expose PCIe device serial number

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Message-ID: <20250915110320.0000602f@huawei.com>
Date: Mon, 15 Sep 2025 11:03:20 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Krzysztof Wilczyński <kw@...ux.com>
CC: Keith Busch <kbusch@...nel.org>, Matthew Wood <thepacketgeek@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Mario Limonciello <superm1@...nel.org>,
	Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>
Subject: Re: [RESEND PATCH v7 1/1] PCI/sysfs: Expose PCIe device serial
 number

On Sat, 13 Sep 2025 15:17:20 +0900
Krzysztof Wilczyński <kw@...ux.com> wrote:

> Hello,
> 
> > Can we get a ruling on this one? It's pretty straight forward
> > implementation exposing a useful attribute.  
> 
> Who needs this?  Why is this useful?  Why hasn't there been a need for
> exposing serial number in past decades, and suddenly we need it so
> desperately?
> 
> We probably wouldn't want to add this if there is only a single user that
> needs this, especially give that userspace tools like lspci already expose
> this when someone needs it.
> 
> Also, we were reluctant to expose some types of information, like serial
> numbers and such, via the VPD recently, so why exposing any serial numbers
> via sysfs would be any different?

I'll note that we already expose these serial numbers for CXL type3 devices
because they are really useful when you have a bunch of identical devices
as they turn in RAS error records and other places.

I pushed back on adding this same sysfs attribute to other CXL types
on basis we could just get it from the associated PCI device (assuming this
series lands).

https://elixir.bootlin.com/linux/v6.17-rc5/source/drivers/cxl/core/memdev.c#L113

Note that we don't do is_visible magic for this particular attribute in CXL
because it is mandated as present by the CXL spec.  We do that for a lot
of other stuff though as it keeps the interface clean.

Jonathan


> 
> Thank you,
> 
> 	Krzysztof