tpm: expose spaces via a device link /dev/tpmrm<n>

Currently the tpm spaces are not exposed to userspace.  Make this
exposure via a separate device, which can now be opened multiple times
because each read/write transaction goes separately via the space.

Concurrency is protected by the chip->tpm_mutex for each read/write
transaction separately.  The TPM is cleared of all transient objects
by the time the mutex is dropped, so there should be no interference
between the kernel and userspace.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index d09cf26365c3..16abbf9cb53a 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -1262,9 +1262,17 @@ static int __init tpm_init(void)
 		return PTR_ERR(tpm_class);
 	}
 
-	rc = alloc_chrdev_region(&tpm_devt, 0, TPM_NUM_DEVICES, "tpm");
+	tpmrm_class = class_create(THIS_MODULE, "tpmrm");
+	if (IS_ERR(tpmrm_class)) {
+		pr_err("couldn't create tpmrm class\n");
+		class_destroy(tpm_class);
+		return PTR_ERR(tpmrm_class);
+	}
+
+	rc = alloc_chrdev_region(&tpm_devt, 0, 2*TPM_NUM_DEVICES, "tpm");
 	if (rc < 0) {
 		pr_err("tpm: failed to allocate char dev region\n");
+		class_destroy(tpmrm_class);
 		class_destroy(tpm_class);
 		return rc;
 	}
@@ -1276,7 +1284,8 @@ static void __exit tpm_exit(void)
 {
 	idr_destroy(&dev_nums_idr);
 	class_destroy(tpm_class);
-	unregister_chrdev_region(tpm_devt, TPM_NUM_DEVICES);
+	class_destroy(tpmrm_class);
+	unregister_chrdev_region(tpm_devt, 2*TPM_NUM_DEVICES);
 }
 
 subsys_initcall(tpm_init);