linux-kernel - [PATCH 1/2] tpm: Implement public tpm_put

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Message-Id: <20180626193040.2509798-2-stefanb@linux.vnet.ibm.com>
Date:   Tue, 26 Jun 2018 15:30:39 -0400
From:   Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:     linux-integrity@...r.kernel.org, jarkko.sakkinen@...ux.intel.com,
        zohar@...ux.vnet.ibm.com, jejb@...ux.vnet.ibm.com
Cc:     jgg@...pe.ca, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, dhowells@...hat.com,
        keyrings@...r.kernel.org,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Stefan Berger <stefanb@...x.vnet.ibm.com>
Subject: [PATCH 1/2] tpm: Implement public tpm_put_chip() to release reference to chip

Some subsystems that got a hold of a TPM chip through tpm_default_chip()
need a way to release the reference to the TPM chip when they shut down.
The tpm_put_chip() function enables this.

Signed-off-by: Stefan Berger <stefanb@...x.vnet.ibm.com>
---
 drivers/char/tpm/tpm-chip.c | 10 ++++++++++
 include/linux/tpm.h         |  4 ++++
 2 files changed, 14 insertions(+)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 46caadca916a..c744289d82e0 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -80,6 +80,16 @@ void tpm_put_ops(struct tpm_chip *chip)
 }
 EXPORT_SYMBOL_GPL(tpm_put_ops);
 
+/**
+ * tpm_put_chip() - Releae a ref to the tpm_chip
+ * @chip: Chip to put
+ */
+void tpm_put_chip(struct tpm_chip *chip)
+{
+	put_device(&chip->dev);
+}
+EXPORT_SYMBOL_GPL(tpm_put_chip);
+
 /**
  * tpm_default_chip() - find a TPM chip and get a reference to it
  */
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index e0e51c49a0e6..889dafe739e1 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -62,6 +62,7 @@ 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);
+extern void tpm_put_chip(struct tpm_chip *chip);
 #else
 static inline int tpm_is_tpm2(struct tpm_chip *chip)
 {
@@ -101,5 +102,8 @@ static inline struct tpm_chip *tpm_default_chip(void)
 {
 	return NULL;
 }
+static inline void tpm_put_chip(struct tpm_chip *chip)
+{
+}
 #endif
 #endif
-- 
2.17.1