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

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Message-ID:
 <PN3PR01MB9597F040DD8F5A9B1A65B397B8D72@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM>
Date: Sun, 9 Mar 2025 09:41:29 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
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 9 Mar 2025, at 3:09 PM, gregkh@...uxfoundation.org wrote:
> 
> 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.

Yes there needs to be a tie, basically first establish a communication with the t2 using bce and then the other 2 come into the picture. I did get a basic idea from what the maintainers want, and this will be some work to do. Thanks for your inputs!
> 
> thanks,
> 
> greg k-h