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Message-ID: <46fcba11-5766-4c7c-91dd-0dfb5ae0e110@linux.ibm.com>
Date:   Thu, 14 Dec 2023 09:37:20 -0600
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Subject: Re: [PATCH v1 2/8] dt-bindings: tpm: Add schema for TIS I2C devices
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To:     Guenter Roeck <linux@roeck-us.net>, Conor Dooley <conor@kernel.org>
Cc:     robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org, joel@jms.id.au, andrew@codeconstruct.com.au,
        peterhuewe@gmx.de, jarkko@kernel.org, jgg@ziepe.ca,
        keescook@chromium.org, tony.luck@intel.com, gpiccoli@igalia.com,
        johannes.holland@infineon.com, broonie@kernel.org,
        patrick.rudolph@9elements.com, vincent@vtremblay.dev,
        peteryin.openbmc@gmail.com, lakshmiy@us.ibm.com,
        bhelgaas@google.com, naresh.solanki@9elements.com,
        alexander.stein@ew.tq-group.com, festevam@denx.de,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        linux-integrity@vger.kernel.org, linux-hardening@vger.kernel.org,
        geissonator@yahoo.com
References: <20231212164004.1683589-1-ninad@linux.ibm.com>
 <20231212164004.1683589-3-ninad@linux.ibm.com>
 <20231212-amusement-elevation-28e42bcccc35@spud>
 <874d4416-86e5-48cc-9c84-97357e4caefe@roeck-us.net>
From:   Ninad Palsule <ninad@linux.ibm.com>
In-Reply-To: <874d4416-86e5-48cc-9c84-97357e4caefe@roeck-us.net>
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Hello Guenter,

On 12/12/23 12:20, Guenter Roeck wrote:
> On Tue, Dec 12, 2023 at 05:14:26PM +0000, Conor Dooley wrote:
>> Hey,
>>
>> On Tue, Dec 12, 2023 at 10:39:58AM -0600, Ninad Palsule wrote:
>>> From: Johannes Holland <johannes.holland@infineon.com>
>>>
>>> Add a dt schema to support device tree bindings
>> "Add bindings for..."
>>
>>> for the generic I2C
>>> physical layer. Refer to the TCG PC Client Platform TPM Profile (PTP)
>>> Specification for TPM 2.0 v1.04 Revision 14.
>>>
>>> This includes descriptions for the Nuvoton and Infineon devices.
>>>
>>> OpenBMC-Staging-Count: 3
>> I have no idea what this is, but it needs to be removed from the patch.
>>
>>> Signed-off-by: Johannes Holland <johannes.holland@infineon.com>
>>> Signed-off-by: Joel Stanley <joel@jms.id.au>
>>> Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
>>> ---
>>>   .../bindings/security/tpm/tpm-tis-i2c.yaml    | 50 +++++++++++++++++++
>>>   1 file changed, 50 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml b/Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml
>>> new file mode 100644
>>> index 000000000000..de1e34065748
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/security/tpm/tpm-tis-i2c.yaml
>>> @@ -0,0 +1,50 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/security/tpm/tpm-tis-i2c.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: I2C PTP based TPM Devices
>>> +
>>> +maintainers:
>>> +  - Johannes Holland <johannes.holland@infineon.com>
>>> +
>>> +description:
>>> +  Device Tree Bindings for I2C based Trusted Platform Module (TPM).
>> s/Device Tree Bindings for //. Doesn't dt_binding_check now complain if
>> you have this in a title or description?
>>
>>> +properties:
>>> +  $nodename:
>>> +    pattern: "^tpm(@[0-9a-f]+)?$"
>>> +
>>> +  compatible:
>>> +    oneOf:
>>> +      - description: Infineon's Trusted Platform Module (TPM) (SLB9673).
>>> +        items:
>>> +          - const: infineon,slb9673
>>> +          - const: tcg,tpm-tis-i2c
>>> +      - description: Nuvoton's Trusted Platform Module (TPM) (NPCT75x).
>>> +        items:
>>> +          - const: nuvoton,npct75x
>>> +          - const: tcg,tpm-tis-i2c
>>> +      - const: tcg,tpm-tis-i2c
>> IMO this should be removed and this fallback should only be used in
>> combination with device specific compatibles, like you have here for the
>> infineon and nuvoton devices.
> As mentioned in my response to the other patch, "only" isn't sufficient
> since the tacoma devicetree file only references the generic entry.
> It would also make support for chips from other vendors unnecessarily
> complex.
>
> Question should in my opinion be if the non-fallback entries are really
> needed.

Thanks for the response. I think generic option is in-case we have a 
chip whose specific driver is not available.

Regards,

Ninad

>
> Thanks,
> Guenter