tpm: device class for tpm

Added own device class for TPM. Uses MISC_MAJOR:TPM_MINOR for the
first character device in order to retain backwards compatibility.
Added tpm_dev_release() back attached to the character device.

I've been running this code now for a while on my laptop (Lenovo
T430S) TrouSerS works perfectly without modifications. I don't
believe it breaks anything significantly.

The sysfs attributes that have been placed under the wrong place
and are against sysfs-rules.txt should be probably left to
stagnate under platform device directory and start defining
new sysfs attributes to the char device directory.

Guidelines for future TPM sysfs attributes should be probably
along the lines of

- Single flat set of mandatory sysfs attributes. For example,
  current PPI interface is way way too rich when you only want
  to use it to clear and activate the TPM.

- Define sysfs attribute if and only if there's no way to get
  the value from ring-3. No attributes for TPM properties. It's
  just unnecessary maintenance hurdle that we don't want.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jasob Gunthorpe <jason.gunthorpe@obsidianresearch.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Tested-by: Scot Doyle <lkml14@scotdoyle.com>
Tested-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index e2af28fd63cb..b6f6b17392fd 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -997,6 +997,35 @@ int tpm_get_random(u32 chip_num, u8 *out, size_t max)
 }
 EXPORT_SYMBOL_GPL(tpm_get_random);
 
+static int __init tpm_init(void)
+{
+	int rc;
+
+	tpm_class = class_create(THIS_MODULE, "tpm");
+	if (IS_ERR(tpm_class)) {
+		pr_err("couldn't create tpm class\n");
+		return PTR_ERR(tpm_class);
+	}
+
+	rc = alloc_chrdev_region(&tpm_devt, 0, TPM_NUM_DEVICES, "tpm");
+	if (rc < 0) {
+		pr_err("tpm: failed to allocate char dev region\n");
+		class_destroy(tpm_class);
+		return rc;
+	}
+
+	return 0;
+}
+
+static void __exit tpm_exit(void)
+{
+	class_destroy(tpm_class);
+	unregister_chrdev_region(tpm_devt, TPM_NUM_DEVICES);
+}
+
+subsys_initcall(tpm_init);
+module_exit(tpm_exit);
+
 MODULE_AUTHOR("Leendert van Doorn (leendert@watson.ibm.com)");
 MODULE_DESCRIPTION("TPM Driver");
 MODULE_VERSION("2.0");