tpm: Add tpm_version_major sysfs file

Easily determining what TCG version a tpm device implements
has been a pain point for userspace for a long time, so
add a sysfs file to report the TCG major version of a tpm device.

Also add an entry to Documentation/ABI/stable/sysfs-class-tpm
describing the new file.

Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Peter Huewe <peterhuewe@gmx.de>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-integrity@vger.kernel.org
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

Documentation/ABI/stable/sysfs-class-tpm

@@ -183,3 +183,14 @@ Description:	The "timeouts" property shows the 4 vendor-specific values
 		The four timeout values are shown in usecs, with a trailing
 		"[original]" or "[adjusted]" depending on whether the values
 		were scaled by the driver to be reported in usec from msecs.
+
+What:		/sys/class/tpm/tpmX/tpm_version_major
+Date:		October 2019
+KernelVersion:	5.5
+Contact:	linux-integrity@vger.kernel.org
+Description:	The "tpm_version_major" property shows the TCG spec major version
+		implemented by the TPM device.
+
+		Example output:
+
+		2

drivers/char/tpm/tpm-sysfs.c

@@ -310,7 +310,17 @@ static ssize_t timeouts_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(timeouts);
 
-static struct attribute *tpm_dev_attrs[] = {
+static ssize_t tpm_version_major_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct tpm_chip *chip = to_tpm_chip(dev);
+
+	return sprintf(buf, "%s\n", chip->flags & TPM_CHIP_FLAG_TPM2
+		       ? "2" : "1");
+}
+static DEVICE_ATTR_RO(tpm_version_major);
+
+static struct attribute *tpm1_dev_attrs[] = {
 	&dev_attr_pubek.attr,
 	&dev_attr_pcrs.attr,
 	&dev_attr_enabled.attr,
@@ -321,18 +331,28 @@ static struct attribute *tpm_dev_attrs[] = {
 	&dev_attr_cancel.attr,
 	&dev_attr_durations.attr,
 	&dev_attr_timeouts.attr,
+	&dev_attr_tpm_version_major.attr,
 	NULL,
 };
 
-static const struct attribute_group tpm_dev_group = {
-	.attrs = tpm_dev_attrs,
+static struct attribute *tpm2_dev_attrs[] = {
+	&dev_attr_tpm_version_major.attr,
+	NULL
+};
+
+static const struct attribute_group tpm1_dev_group = {
+	.attrs = tpm1_dev_attrs,
+};
+
+static const struct attribute_group tpm2_dev_group = {
+	.attrs = tpm2_dev_attrs,
 };
 
 void tpm_sysfs_add_device(struct tpm_chip *chip)
 {
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
-		return;
-
 	WARN_ON(chip->groups_cnt != 0);
-	chip->groups[chip->groups_cnt++] = &tpm_dev_group;
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		chip->groups[chip->groups_cnt++] = &tpm2_dev_group;
+	else
+		chip->groups[chip->groups_cnt++] = &tpm1_dev_group;
 }