linux-kernel - Re: [PATCH] tpm, tpm_tis: fix TPM 2.0 probing

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Message-ID: <54D9F6A0.9010905@linux.vnet.ibm.com>
Date:	Tue, 10 Feb 2015 07:16:32 -0500
From:	Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Peter Hüwe <PeterHuewe@....de>
CC:	Ashley Lai <ashley@...leylai.com>,
	Marcel Selhorst <tpmdd@...horst.net>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	josh@...htriplett.org, christophe.ricard@...il.com,
	jason.gunthorpe@...idianresearch.com, linux-api@...r.kernel.org,
	trousers-tech@...ts.sourceforge.net
Subject: Re: [PATCH] tpm, tpm_tis: fix TPM 2.0 probing

On 02/09/2015 03:39 AM, Jarkko Sakkinen wrote:
> On Mon, Feb 09, 2015 at 12:08:46AM +0100, Peter Hüwe wrote:
>> Am Mittwoch, 4. Februar 2015, 15:21:09 schrieb Jarkko Sakkinen:
>>> If during transmission system error was returned, the logic was to
>>> incorrectly deduce that chip is a TPM 1.x chip. This patch fixes this
>>> issue. Also, this patch changes probing so that message tag is used as the
>>> measure for TPM 2.x, which should be much more stable.
>> Is it aware that some TPMs may respond with 0x00C1 as TAG for TPM1.2 commands?
> I guess none of the TPM 1.2 command answer with the tag 0x8002?


FYI: pdf page 26 , section 6.1 explains the predictable return value for 
a TPM1.2 command seen by a TPM2

http://www.trustedcomputinggroup.org/files/static_page_files/8C68ADA8-1A4B-B294-D0FC06D3773F7DAA/TPM%20Rev%202.0%20Part%203%20-%20Commands%2001.16-code.pdf

Following this:

Sending a TPM1.2 command to a TPM2 should return a TPM1.2 header (tag = 
0xc4) and error code (TPM_BADTAG = 0x1e)

Sending a TPM 2 command to a TPM 2 will give a TPM 2 tag in the header.
Sending a TPM 2 command to a TPM 1.2 will give a TPM 1.2 tag in the 
header and an error code.


    Stefan

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