Re: [PATCH v2 2/3] tpm: Address !chip->auth in tpm_buf_append_name()

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2024-07-03 at 21:24 +0300, Jarkko Sakkinen wrote:
[...]
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 21a67dc9efe8..2844fea4a12a 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -211,8 +211,8 @@ struct tpm_chip {
>         u8 null_key_name[TPM2_NAME_SIZE];
>         u8 null_ec_key_x[EC_PT_SZ];
>         u8 null_ec_key_y[EC_PT_SZ];
> -       struct tpm2_auth *auth;
>  #endif
> +       struct tpm2_auth *auth;
>  };

Since auth should only be present if CONFIG_TCG_TPM2_HMAC this is
clearly an undesirable thing to do.  I think you did it because in a
later patch you want to collapse the hmac sessions to use a single
routine, but you can make that check with the preprocessor __and
function defined in kconfig.h:

if (__and(IS_ENABLED(CONFIG_TCG_TPM2_HMAC), chip->auth))

Which will become 0 if the config is not enabled and chip->auth if it
is, thus eliminating the code in the former case while not causing the
compiler to complain about chip->auth not being defined even if it's
under the config parameter.

James