Re: [PATCH] PCI: ACPI: Allow internal devices to be marked as untrusted - Jean-Philippe Brucker

From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Rajat Jain <rajatja@google.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bjorn Helgaas <helgaas@kernel.org>, Len Brown <lenb@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
	Linux PCI <linux-pci@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Rajat Jain <rajatxjain@gmail.com>,
	Dmitry Torokhov <dtor@google.com>,
	Jesse Barnes <jsbarnes@google.com>, Pavel Machek <pavel@denx.de>,
	Oliver O'Halloran <oohall@gmail.com>,
	Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH] PCI: ACPI: Allow internal devices to be marked as untrusted
Date: Fri, 28 Jan 2022 09:55:32 +0000	[thread overview]
Message-ID: <YfO9lPJe0RuVyxFf@myrica> (raw)
In-Reply-To: <CACK8Z6H2DLTJgxgS3pcvfOh=5S8cxEMKvwEPfB9zoVf1g2H_UQ@mail.gmail.com>

On Thu, Jan 27, 2022 at 02:26:07PM -0800, Rajat Jain wrote:
> > > > And shouldn't this be an ACPI standard?
> > >
> > > Probably should or some supplemental doc but not sure how easy these
> > > "properties" can be added there to be honest.
> 
> AIUI, the principal comment I have received here is that this property
> needs to be documented somewhere. I agree.
> 
> Rafael, do you know if this new property can be added to the ACPI
> spec, and if so, how to do so? I'm happy to initiate a process if
> someone can point me to, I just hope that publishing a new property to
> the ACPI does not have to block this patch.
> 
> The other option I was thinking of was to use the same property name
> (say "untrusted-device") for both ACPI and device tree platforms, and
> document it in Documentation/devicetree/bindings/pci/pci.txt along
> with others. Since there are other properties there that seem to be
> used similarly (Mika highlighted some below), perhaps that is an
> acceptable solution?
> 
> I had one last question on the property name itself. I was trying to
> understand why a property might have 2 names i.e. "external-facing"
> for DT and "ExternalFacingPort" in ACPI?

I picked "external-facing" for DT to be consistent with other device tree
property names. There doesn't seem to be any CamelCase in device trees
[1], so we should probably keep that convention for new properties as
well. The internal device_property could use the DT name and the ACPI name
can be different. We do something similar with properties "pasid-num-bits"
and "dma-can-stall" which are extracted from the IORT table in
iort_named_component_init()

Thanks,
Jean

[1] git grep "\<[A-Z][,a-zA-Z0-9]\+ =" -- '*.dts'

> Are there any naming
> convention requirements that require ACPI and DT property names to be
> different? Is "untrusted-device" an acceptable ACPI property name?
> 
> Thanks & Best Regards,
> 
> Rajat