linux-kernel - [PATCH v3 2/4] tpm: Implement tpm_chip_find() for other subsystems to find a TPM chip

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Message-Id: <20180622164613.1609313-3-stefanb@linux.vnet.ibm.com>
Date:   Fri, 22 Jun 2018 12:46:11 -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
Cc:     jgg@...pe.ca, linux-kernel@...r.kernel.org,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>
Subject: [PATCH v3 2/4] tpm: Implement tpm_chip_find() for other subsystems to find a TPM chip

Implement tpm_chip_find() for other subsystems to find a TPM chip and
get a reference to that chip.

Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
---
 drivers/char/tpm/tpm-chip.c | 27 +++++++++++++++++++++++++++
 include/linux/tpm.h         |  5 +++++
 2 files changed, 32 insertions(+)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 4e83695af068..2520555b1e17 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -81,6 +81,33 @@ void tpm_put_ops(struct tpm_chip *chip)
 EXPORT_SYMBOL_GPL(tpm_put_ops);
 
 /**
+ * tpm_chip_find() - find a TPM chip and get a reference to it
+ */
+struct tpm_chip *tpm_chip_find(void)
+{
+	struct tpm_chip *chip, *res = NULL;
+	int chip_num = 0;
+	int chip_prev;
+
+	mutex_lock(&idr_lock);
+
+	do {
+		chip_prev = chip_num;
+		chip = idr_get_next(&dev_nums_idr, &chip_num);
+		if (chip) {
+			get_device(&chip->dev);
+			res = chip;
+			break;
+		}
+	} while (chip_prev != chip_num);
+
+	mutex_unlock(&idr_lock);
+
+	return res;
+}
+EXPORT_SYMBOL_GPL(tpm_chip_find);
+
+/**
  * tpm_get_ops() - find and reserve a TPM chip
  * @chip:	a &struct tpm_chip instance, %NULL for the default chip
  *
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 06639fb6ab85..a9c65f5670b6 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -61,6 +61,7 @@ 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_chip_find(void);
 #else
 static inline int tpm_is_tpm2(struct tpm_chip *chip)
 {
@@ -96,5 +97,9 @@ static inline int tpm_unseal_trusted(struct tpm_chip *chip,
 {
 	return -ENODEV;
 }
+static inline struct tpm_chip *tpm_chip_find(void)
+{
+	return NULL;
+}
 #endif
 #endif
-- 
2.13.6