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Subject[PATCH v4] tpm: Add tpm_version_major sysfs file
Date
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>
---
v4: - Change file name to tpm_version_major
- Actually display just the major version.
- change structs to tpm1_* & tpm2_*
instead of tpm12_* tpm20_*.
v3: - Change file name to version_major.
v2: - Fix TCG usage in commit message.
- Add entry to sysfs-class-tpm in Documentation/ABI/stable

Documentation/ABI/stable/sysfs-class-tpm | 11 ++++++++
drivers/char/tpm/tpm-sysfs.c | 34 +++++++++++++++++++-----
2 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/Documentation/ABI/stable/sysfs-class-tpm b/Documentation/ABI/stable/sysfs-class-tpm
index c0e23830f56a..5468fedc493c 100644
--- a/Documentation/ABI/stable/sysfs-class-tpm
+++ b/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
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index edfa89160010..12da71e72488 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -309,7 +309,17 @@ 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,
@@ -320,18 +330,28 @@ 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;
}
--
2.23.0
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