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

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Message-ID:
 <PN3PR01MB9597B64008E01DC0336FAE37B8D72@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM>
Date: Sun, 9 Mar 2025 10:12:06 +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 3:26 PM, gregkh@...uxfoundation.org wrote:
> 
> On Sun, Mar 09, 2025 at 09:52:43AM +0000, Aditya Garg wrote:
>> 
>> 
>>>> On 9 Mar 2025, at 3:21 PM, gregkh@...uxfoundation.org wrote:
>>> 
>>> On Sun, Mar 09, 2025 at 09:41:29AM +0000, Aditya Garg wrote:
>>>> 
>>>> 
>>>>>> 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!
>>> 
>>> If there is "communication" then that's a bus in the driver model
>>> scheme, so just use that, right?
>> 
>> So basically RE the whole driver to see what exactly should be use?
> 
> I'm sorry, I can not parse this.


I was asking that should I introduce a completely new bus instead of pci and probably reverse engineer the original macOS driver to see what exactly is going on there?

I might not have been clear, but I'm not the author of this patch.