linux-kernel - Re: [PATCH v7 6/7] tpm: Add YAML schema for TPM TIS I2C options

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Date:   Wed, 6 May 2020 15:20:30 +0000
From:   Amir Mizinski <amirmizi6@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Eyal.Cohen@...oton.com, jarkko.sakkinen@...ux.intel.com,
        oshrialkoby85@...il.com, alexander.steffen@...ineon.com,
        mark.rutland@....com, peterhuewe@....de, jgg@...pe.ca,
        arnd@...db.de, gregkh@...uxfoundation.org, benoit.houyere@...com,
        eajames@...ux.ibm.com, joel@....id.au, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        oshri.alkoby@...oton.com, tmaimon77@...il.com, gcwilson@...ibm.com,
        kgoldman@...ibm.com, Dan.Morav@...oton.com,
        oren.tanami@...oton.com, shmulik.hager@...oton.com,
        amir.mizinski@...oton.com
Subject: Re: [PATCH v7 6/7] tpm: Add YAML schema for TPM TIS I2C options


On 2020-05-05 16:12, Rob Herring wrote:
> On Mon, Apr 27, 2020 at 03:49:30PM +0300, amirmizi6@...il.com wrote:
>> From: Amir Mizinski <amirmizi6@...il.com>
>>
>> Added a YAML schema to support tpm tis i2c related dt-bindings for the I2c
>> PTP based physical layer.
>>
>> This patch adds the documentation for corresponding device tree bindings of
>> I2C based Physical TPM.
>> Refer to the 'I2C Interface Definition' section in
>> 'TCG PC Client PlatformTPMProfile(PTP) Specification' publication
>> for specification.
>
> Again, DT bindings describe h/w devices, not just a protocol. A device
> is more than just a protocol interface. There's clocks, power rails,
> resets, interrupts, firmware, etc.
>
> Unless there's something special about TPM chips that makes none of this
> applicable and no chip will ever have any quirks (or extensions) in
> their protocol to work-around, then you need compatible string(s) that
> are specific to the TPM chip. You can have tcg,tpm-tis-i2c as a
> fallback, but you need specific compatible to handle any quirks.
>
> Rob

Hello Rob, currently yes. All TPM chip are implemented according to the TGC specs and should use the same properties for this I2C driver.
I can't say for sure that it will be the case in the future. Shouldn't we use the standard "tcg,tpm-tis-i2c" compatible, and if a specific TPM chip will deviate from the specs, the vendor should add an additional compatible string for it?
Thank you,
Amir