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

["Jarkko Sakkinen" <jarkko@kernel.org>]

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@oracle.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.

 BR, Jarkko