tpm: Implement tpm_default_chip() to find a TPM chip

Implement tpm_default_chip() to find the first TPM chip and return it to
the caller while increasing the reference count on its device. This
function can be used by other subsystems, such as IMA, to find the system's
default TPM chip and use it for all subsequent TPM operations.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 8eb5e5ebe136..4609b94142d4 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -63,6 +63,7 @@ extern int tpm_seal_trusted(struct tpm_chip *chip,
 extern int tpm_unseal_trusted(struct tpm_chip *chip,
                               struct trusted_key_payload *payload,
                               struct trusted_key_options *options);
+extern struct tpm_chip *tpm_default_chip(void);
 #else
 static inline int tpm_is_tpm2(struct tpm_chip *chip)
 {
@@ -98,5 +99,9 @@ static inline int tpm_unseal_trusted(struct tpm_chip *chip,
 {
         return -ENODEV;
 }
+static inline struct tpm_chip *tpm_default_chip(void)
+{
+        return NULL;
+}
 #endif
 #endif