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

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Message-ID: <20150210125037.GB4313@intel.com>
Date:	Tue, 10 Feb 2015 14:50:37 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Stefan Berger <stefanb@...ux.vnet.ibm.com>
Cc:	Peter Hüwe <PeterHuewe@....de>,
	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 Tue, Feb 10, 2015 at 07:16:32AM -0500, Stefan Berger wrote:
> 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.

Thank you for the information. Do you think that for some reason
tpm2_probe() shoould instead check that value is not this error
instead of checking that tag is 0x80002?

>    Stefan

/Jarkko
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