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

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Message-ID: <aMgiqJVWTptU6Fq0@kbusch-mbp>
Date: Mon, 15 Sep 2025 08:28:56 -0600
From: Keith Busch <kbusch@...nel.org>
To: Krzysztof Wilczy´nski <kw@...ux.com>
Cc: Matthew Wood <thepacketgeek@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mario Limonciello <superm1@...nel.org>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	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, Sep 13, 2025 at 03:17:20PM +0900, Krzysztof Wilczy´nski wrote:
> Who needs this?  Why is this useful?  Why hasn't there been a need for
> exposing serial number in past decades,

I can't speak for other reviewers for their interest in having such an
attribute. Matt provided the reasoning here in the cover letter by
making it possible to access from unpriviledged applications that are
managing devices assigned to them without jumping through hoops to get
that information.

> and suddenly we need it so desperately?

"desperately" is a bit of a stretch. This simple patch has been out for
many months now, missed 2 merge windows with zero negative feedback, and
we're about to miss a 3rd. At this point, "frustration" would be a
better description.

> We probably wouldn't want to add this if there is only a single user that
> needs this, 

There's multiple reviewers representing different companies.

> especially give that userspace tools like lspci already expose
> this when someone needs it.

Only if you're root. This new attribute is admin-only by default too,
but can be changed as needed.

> 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?

It's a specification defined attribute of a device, and sysfs is the
interface that exports device attributes.