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Date:   Sat, 7 May 2022 22:43:48 +0300
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@infineon.com>
Cc:     linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
        Marten.Lindahl@axis.com, martenli@axis.com, jgg@ziepe.ca,
        jsnitsel@redhat.com, nayna@linux.vnet.ibm.com,
        johannes.holland@infineon.com, peterhuewe@gmx.de
Subject: Re: [PATCH 2/2] tpm: Add Field Upgrade mode support for Infineon
 TPM2 modules
Message-ID: <YnbL9LwDkY+MHdkK@iki.fi>
References: <20220506123145.229058-1-stefan.mahnke-hartmann@infineon.com>
 <20220506123145.229058-2-stefan.mahnke-hartmann@infineon.com>
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On Fri, May 06, 2022 at 02:31:48PM +0200, Stefan Mahnke-Hartmann wrote:
> TPM2_GetCapability with a capability that has the property type value
> of TPM_PT_TOTAL_COMMANDS returns a zero length list, when an Infineon
> TPM2 is in Field Upgrade mode.
> Since an Infineon TPM2.0 in Field Upgrade mode returns RC_SUCCESS on
> TPM2_Startup, the Field Upgrade mode has to be detected by
> TPM2_GetCapability.
> 
> Signed-off-by: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@infineon.com>
> ---
>  drivers/char/tpm/tpm2-cmd.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index e62a644ce26b..659130e2936e 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -746,6 +746,12 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>  	}
>  
>  	rc = tpm2_get_cc_attrs_tbl(chip);
> +	/*
> +	 * Infineon TPM in Field Upgrade mode will return no data for the number
> +	 * of supported commands.
> +	 */
> +	if (rc == -ENODATA)
> +		rc = TPM2_RC_UPGRADE;

Injecting hardware error codes like this is not considered a great idea.

>  
>  out:
>  	if (rc == TPM2_RC_UPGRADE) {
> -- 
> 2.25.1
> 

BR, Jarkko