linux-kernel - Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

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Date: Thu, 18 Jan 2024 08:12:56 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Esther Shimanovich <eshimanovich@...omium.org>,
	Lukas Wunner <lukas@...ner.de>, Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rajat Jain <rajatja@...gle.com>
Subject: Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

On Thu, Jan 18, 2024 at 09:47:07AM -0600, Mario Limonciello wrote:
> On 1/18/2024 00:00, Mika Westerberg wrote:
> > > Before my patch, you see that the JHL6540 controller is inaccurately
> > > labeled “removable”:
> > > $ udevadm info -a -p /sys/bus/pci/devices/0000:05:00.0 | grep -e
> > > {removable} -e {device} -e {vendor} -e looking
> > >    looking at device '/devices/pci0000:00/0000:00:1d.4/0000:05:00.0':
> > >      ATTR{device}=="0x15d3"
> > >      ATTR{removable}=="removable"
> > >      ATTR{vendor}=="0x8086"
> > 
> > This is actually accurate. The Thunderbolt controller is itself
> > hot-removable and that BTW happens to be hot-removed when fwupd applies
> > firmware upgrades to the device.

This is quite interesting take. Does fwupd rip the controller out of the
box to update it? By that account your touchpad is also removable as it
may stop functioning when its firmware gets updated.

> 
> Depending on the consumers of this removable attribute I wonder if we need
> to a new ATTR of "external" instead of overloading "removable".

Isn't this the same thing? From
Documentation/ABI/testing/sysfs-devices-removable:

What:		/sys/devices/.../removable
Date:		May 2021
Contact:	Rajat Jain <rajatxjain@...il.com>
Description:
		Information about whether a given device can be removed from the
		platform by the	user. This is determined by its subsystem in a
		bus / platform-specific way. This attribute is only present for
		devices that can support determining such information:

		===========  ===================================================
		"removable"  device can be removed from the platform by the user
		"fixed"      device is fixed to the platform / cannot be removed
			     by the user.

Note this "by the user". Maybe we should add word "physically" here to
qualify the meaning completely, but that is what it is. Not that it
disappears from the bus or stops operating for some time because of
firmware updates, but it can be physically detached from the
platform/system.

Thanks.

-- 
Dmitry