linux-kernel - Re: [PATCH v9 16/19] tpm: Add ability to set the preferred locality the TPM chip uses

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Date: Tue, 4 Jun 2024 15:14:38 -0700
From: ross.philipson@...cle.com
To: Jarkko Sakkinen <jarkko@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-integrity@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-crypto@...r.kernel.org,
        kexec@...ts.infradead.org, linux-efi@...r.kernel.org,
        iommu@...ts.linux-foundation.org
Cc: dpsmith@...rtussolutions.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, dave.hansen@...ux.intel.com,
        ardb@...nel.org, mjg59@...f.ucam.org,
        James.Bottomley@...senpartnership.com, peterhuewe@....de, jgg@...pe.ca,
        luto@...capital.net, nivedita@...m.mit.edu,
        herbert@...dor.apana.org.au, davem@...emloft.net, corbet@....net,
        ebiederm@...ssion.com, dwmw2@...radead.org, baolu.lu@...ux.intel.com,
        kanth.ghatraju@...cle.com, andrew.cooper3@...rix.com,
        trenchboot-devel@...glegroups.com, ross.philipson@...cle.com
Subject: Re: [PATCH v9 16/19] tpm: Add ability to set the preferred locality
 the TPM chip uses

On 6/4/24 1:27 PM, Jarkko Sakkinen wrote:
> On Fri May 31, 2024 at 4:03 AM EEST, Ross Philipson wrote:
>> Curently the locality is hard coded to 0 but for DRTM support, access
>> is needed to localities 1 through 4.
>>
>> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
>> ---
>>   drivers/char/tpm/tpm-chip.c      | 24 +++++++++++++++++++++++-
>>   drivers/char/tpm/tpm-interface.c | 15 +++++++++++++++
>>   drivers/char/tpm/tpm.h           |  1 +
>>   include/linux/tpm.h              |  4 ++++
>>   4 files changed, 43 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
>> index 854546000c92..73eac54d61fb 100644
>> --- a/drivers/char/tpm/tpm-chip.c
>> +++ b/drivers/char/tpm/tpm-chip.c
>> @@ -44,7 +44,7 @@ static int tpm_request_locality(struct tpm_chip *chip)
>>   	if (!chip->ops->request_locality)
>>   		return 0;
>>   
>> -	rc = chip->ops->request_locality(chip, 0);
>> +	rc = chip->ops->request_locality(chip, chip->pref_locality);
>>   	if (rc < 0)
>>   		return rc;
>>   
>> @@ -143,6 +143,27 @@ void tpm_chip_stop(struct tpm_chip *chip)
>>   }
>>   EXPORT_SYMBOL_GPL(tpm_chip_stop);
>>   
>> +/**
>> + * tpm_chip_preferred_locality() - set the TPM chip preferred locality to open
>> + * @chip:	a TPM chip to use
>> + * @locality:   the preferred locality
>> + *
>> + * Return:
>> + * * true      - Preferred locality set
>> + * * false     - Invalid locality specified
>> + */
>> +bool tpm_chip_preferred_locality(struct tpm_chip *chip, int locality)
>> +{
>> +	if (locality < 0 || locality >=TPM_MAX_LOCALITY)
>> +		return false;
>> +
>> +	mutex_lock(&chip->tpm_mutex);
>> +	chip->pref_locality = locality;
>> +	mutex_unlock(&chip->tpm_mutex);
>> +	return true;
>> +}
>> +EXPORT_SYMBOL_GPL(tpm_chip_preferred_locality);
>> +
>>   /**
>>    * tpm_try_get_ops() - Get a ref to the tpm_chip
>>    * @chip: Chip to ref
>> @@ -374,6 +395,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>>   	}
>>   
>>   	chip->locality = -1;
>> +	chip->pref_locality = 0;
>>   	return chip;
>>   
>>   out:
>> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> index 5da134f12c9a..35f14ccecf0e 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -274,6 +274,21 @@ int tpm_is_tpm2(struct tpm_chip *chip)
>>   }
>>   EXPORT_SYMBOL_GPL(tpm_is_tpm2);
>>   
>> +/**
>> + * tpm_preferred_locality() - set the TPM chip preferred locality to open
>> + * @chip:	a TPM chip to use
>> + * @locality:   the preferred locality
>> + *
>> + * Return:
>> + * * true      - Preferred locality set
>> + * * false     - Invalid locality specified
>> + */
>> +bool tpm_preferred_locality(struct tpm_chip *chip, int locality)
>> +{
>> +	return tpm_chip_preferred_locality(chip, locality);
>> +}
>> +EXPORT_SYMBOL_GPL(tpm_preferred_locality);
> 
>   What good does this extra wrapping do?
> 
>   tpm_set_default_locality() and default_locality would make so much more
>   sense in any case.

Are you mainly just talking about my naming choices here and in the 
follow-on response? Can you clarify what you are requesting?

Thanks
Ross

> 
>   BR, Jarkko