linux-kernel - Re: [PATCH RFC] staging: Add driver to communicate with the T2 Security Chip

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Message-ID: <2025030935-contently-handbrake-9239@gregkh>
Date: Sun, 9 Mar 2025 10:37:55 +0100
From: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To: Aditya Garg <gargaditya08@...e.com>
Cc: "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"joro@...tes.org" <joro@...tes.org>,
	"will@...nel.org" <will@...nel.org>,
	"robin.murphy@....com" <robin.murphy@....com>,
	"andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>,
	"linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	Aun-Ali Zaidi <admin@...eit.net>, "paul@...rm.io" <paul@...rm.io>,
	Orlando Chamberlain <orlandoch.dev@...il.com>
Subject: Re: [PATCH RFC] staging: Add driver to communicate with the T2
 Security Chip

On Sun, Mar 09, 2025 at 09:28:01AM +0000, Aditya Garg wrote:
> 
> 
> > On 9 Mar 2025, at 2:46 PM, gregkh@...uxfoundation.org wrote:
> > 
> > On Sun, Mar 09, 2025 at 09:03:29AM +0000, Aditya Garg wrote:
> >> 
> >> 
> >>>> On 9 Mar 2025, at 2:24 PM, gregkh@...uxfoundation.org wrote:
> >>> 
> >>> On Sun, Mar 09, 2025 at 08:40:31AM +0000, Aditya Garg wrote:
> >>>> From: Paul Pawlowski <paul@...rm.io>
> >>>> 
> >>>> This patch adds a driver named apple-bce, to add support for the T2
> >>>> Security Chip found on certain Macs.
> >>>> 
> >>>> The driver has 3 main components:
> >>>> 
> >>>> BCE (Buffer Copy Engine) - this is what the files in the root directory
> >>>> are for. This estabilishes a basic communication channel with the T2.
> >>>> VHCI and Audio both require this component.
> >>> 
> >>> So this is a new "bus" type?  Or a platform resource?  Or something
> >>> else?
> >> 
> >> It's a PCI device
> > 
> > Great, but then is the resources split up into smaller drivers that then
> > bind to it?  How does the other devices talk to this?
> 
> We technically can split up these 3 into separate drivers and put then into their own trees.

That's fine, but you say that the bce code is used by the other drivers,
right?  So there is some sort of "tie" between these, and that needs to
be properly conveyed in the device tree in sysfs as that will be
required for proper resource management.

thanks,

greg k-h