Re: [PATCH v3 04/12] PCI: Drop the `is_thunderbolt` attribute from PCI core

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi Mario,

On Sun, Feb 13, 2022 at 11:26:56AM -0600, Limonciello, Mario wrote:
> On 2/13/2022 02:20, Lukas Wunner wrote:
> > On Fri, Feb 11, 2022 at 01:32:42PM -0600, Mario Limonciello wrote:
> > > The `is_thunderbolt` attribute is currently a dumping ground for a
> > > variety of things.
> > 
> > It's not as arbitrary as it may seem.  Quite a bit of thought went into
> > the current design.
> > 
> > 
> > > Instead use the driver core removable attribute to indicate the
> > > detail a device is attached to a thunderbolt or USB4 chain.
> > 
> > You're missing the point that "is_thunderbolt" is set on the *controller*
> > (i.e. its upstream and downstream ports).
> > 
> > The controller itself is *not* removable if it's the host controller.
> > 
> > However a device can be assumed to be removable if it has an ancestor
> > which has the "is_thunderbolt" flag set.
> > 
> 
> Ah right... I wonder if really what this series should be about then is
> setting up the the PCIe endpoints for PCIe tunneling and XHCI tunneling to
> be marked as "external" instead then.  It would mean that existing code will
> apply the removable attribute to everything downstream (and presumably at
> least some of those drivers it will continue to make sense to drop
> "pcie_is_thunderbolt_attached" and instead check dev_is_removable.

Yes, I think this is the right thing to do. Anything connected over
PCIe/USB 3.x tunnel is pretty much "removable" whereas the host
controllers may or may not. Typically they are not.