linux-kernel - Re: [PATCH v2] PCI/IDE: Fix duplicate stream symlink names for TSM class devices

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Message-ID: <aXLtILY85oMU5qlb@yilunxu-OptiPlex-7050>
Date: Fri, 23 Jan 2026 11:38:08 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: dan.j.williams@...el.com
Cc: linux-coco@...ts.linux.dev, linux-pci@...r.kernel.org,
	yilun.xu@...el.com, baolu.lu@...ux.intel.com,
	zhenzhong.duan@...el.com, linux-kernel@...r.kernel.org,
	yi1.lai@...el.com, helgaas@...nel.org
Subject: Re: [PATCH v2] PCI/IDE: Fix duplicate stream symlink names for TSM
 class devices

On Thu, Jan 22, 2026 at 05:07:01PM -0800, dan.j.williams@...el.com wrote:
> dan.j.williams@ wrote:
> [..]
> > However, after seeing Jonathan's feedback and noticing that he missed
> > that 'H' 'R' and 'E' are documented in the host bridge ABI I think it
> > would be better to simplify this to just a link back to the host bridge.
> > 
> >     /sys/class/tsm/tsmN/pciDDDD:BB => /sys/devices/pciDDDD:BB
> > 
> > That achieves the same result and is easier to document as "When a TSM
> > has a established any IDE stream it links to the host bridge. When the
> > last stream is removed the link is removed." It achieves the goal of
> > letting an admin do "ls /sys/class/tsm/tsmN/*/stream*" to get a survey
> > of all consumed stream resources in the system.
> 
> In fact it does not even need to be dynamic. At tsm_register() time when
> @pci_ops is provided, link all host bridges. Unlink them at unregister

I'm sort of supporting dynamic. My DUT has 40 host bridges registered,
most of them has nothing to do with TSM/IDE, so I'm afraid if it is
overkill to list them all, and bury the real TSM capable bridge in the
noise.

And if TSM always list all bridges then why we need these symlinks, we
can just:

  ls -d /sys/devices/pci*\:*/stream*


I assume the annoying part of dynamic is we need to refcount, which IMHO
unnecessarily complex and you are trying to avoid, is it?

> time. The only driving need for it to be dynamic is if there is ever a
> platform that supports multiple TSMs each supporting a different set of
> host bridges. Can cross that bridge later.