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>

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 242b716aed5e51f55d08d615f1b0e9b0851e6d94..f551061262c930629ea87d04dffda8a42b929b3d 100644 (file)
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -80,6 +80,33 @@ void tpm_put_ops(struct tpm_chip *chip)
 }
 EXPORT_SYMBOL_GPL(tpm_put_ops);
 
+/**
+ * tpm_default_chip() - find a TPM chip and get a reference to it
+ */
+struct tpm_chip *tpm_default_chip(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_default_chip);
+
 /**
  * tpm_find_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 8eb5e5ebe136bd23ed72ff29a1572503a016175b..4609b94142d4a74dc2e5960e1a119b4f5f1efbaf 100644 (file)
--- 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