[PATCH] tpm: Add sysfs interface to show TPM hardware version

[Meng.Li]

From: Limeng <Meng.Li@xxxxxxxxxxxxx>

So far, there is not a sysfs interface for user space code to
check the TPM hardware version(TPM1.x or TPM2). So, add a
file named description in /sys/class/tpm/tpmX/ to show it.

Signed-off-by: Meng Li <Meng.Li@xxxxxxxxxxxxx>
---
 drivers/char/tpm/tpm-chip.c |   85 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index c406343..da2cd69 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -36,6 +36,83 @@
 dev_t tpm_devt;
 
 /**
+ * show_description - sysfs interface for checking current TPM hardware version.
+ * @dev:	pointer to tpm chip device
+ * @attr:	unused
+ * @buf:	char buffer to be filled with TPM hardware version info
+ *
+ * Provides sysfs interface for showing current TPM hardware version.
+ */
+static ssize_t show_description(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct tpm_chip *chip = (struct tpm_chip *)container_of(dev,struct tpm_chip,dev);
+	int ret;
+
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		ret = sprintf(buf, "TPM 2.0");
+	else
+		ret = sprintf(buf, "TPM 1.x");
+
+	return ret;
+}
+
+/**
+ * store_description - interface for manually setting data.
+ * @dev:	unused
+ * @attr:	unused
+ * @buf:	unused
+ * @count:	unused
+ *
+ * There is not any process in this function, reserve for feature.
+ */
+static ssize_t store_description(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	return count;
+}
+
+static struct device_attribute tpm_attrs[] = {
+	__ATTR(description, S_IRUGO | S_IWUSR, show_description, store_description),
+};
+
+/**
+ * tpm_create_sysfs - Create tpm sysfs interface.
+ * @dev:	pointer to tpm chip device
+ *
+ * Create sysfs interface for checking current TPM hardware version.
+ */
+static int tpm_create_sysfs(struct device *dev)
+{
+	int r, t;
+
+	for (t = 0; t < ARRAY_SIZE(tpm_attrs); t++) {
+		r = device_create_file(dev, &tpm_attrs[t]);
+		if (r) {
+			dev_err(dev, "failed to create sysfs file\n");
+			return r;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * tpm_remove_sysfs - Remove tpm sysfs interface.
+ * @dev:	pointer to tpm chip device
+ *
+ * Remove sysfs interface for checking current TPM hardware version.
+ */
+static void tpm_remove_sysfs(struct device *dev)
+{
+	int  t;
+
+	for (t = 0; t < ARRAY_SIZE(tpm_attrs); t++) {
+		device_remove_file(dev, &tpm_attrs[t]);
+	}
+}
+
+/**
  * tpm_try_get_ops() - Get a ref to the tpm_chip
  * @chip: Chip to ref
  *
@@ -363,6 +440,13 @@ int tpm_chip_register(struct tpm_chip *chip)
 		return rc;
 	}
 
+	rc = tpm_create_sysfs(&chip->dev);
+	if (rc) {
+		tpm_del_legacy_sysfs(chip);
+		tpm_chip_unregister(chip);
+		return rc;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_chip_register);
@@ -382,6 +466,7 @@ int tpm_chip_register(struct tpm_chip *chip)
  */
 void tpm_chip_unregister(struct tpm_chip *chip)
 {
+	tpm_remove_sysfs(&chip->dev);
 	tpm_del_legacy_sysfs(chip);
 	tpm_bios_log_teardown(chip);
 	tpm_del_char_device(chip);
-- 
1.7.9.5