[RFC PATCH 10/10] CHROMIUM: wilco_ec: Add binary telemetry attributes

[Nick Crews]

The Wilco Embedded Controller is able to send telemetry data
which is useful for enterprise applications. A daemon running on
the OS sends a command (possibly with args) to the EC via
this sysfs interface, and the EC responds over the sysfs interface
with the response. Both the request and the response are in an opaque
binary format so that information which is proprietary to the
enterprise service provider is secure.

At this point, the Wilco EC does not implement this telemetry
functionality, so any request using the WILCO_EC_MSG_TELEMETRY
command returns an error. This is just an initial change for
comments, until the EC code is implemented.

Signed-off-by: Nick Crews <ncrews@xxxxxxxxxx>
---

 drivers/platform/chrome/Makefile             |  3 +-
 drivers/platform/chrome/wilco_ec_sysfs.c     | 17 ++++-
 drivers/platform/chrome/wilco_ec_telemetry.c | 66 ++++++++++++++++++++
 drivers/platform/chrome/wilco_ec_telemetry.h | 42 +++++++++++++
 4 files changed, 126 insertions(+), 2 deletions(-)
 create mode 100644 drivers/platform/chrome/wilco_ec_telemetry.c
 create mode 100644 drivers/platform/chrome/wilco_ec_telemetry.h

diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index c9d3d44098f9..62444887ce18 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -17,5 +17,6 @@ wilco_ec-objs				:= wilco_ec_mailbox.o wilco_ec_event.o \
 					   wilco_ec_rtc.o wilco_ec_legacy.o \
 					   wilco_ec_sysfs.o \
 					   wilco_ec_properties.o \
-					   wilco_ec_adv_power.o
+					   wilco_ec_adv_power.o  \
+					   wilco_ec_telemetry.o
 obj-$(CONFIG_WILCO_EC)			+= wilco_ec.o
diff --git a/drivers/platform/chrome/wilco_ec_sysfs.c b/drivers/platform/chrome/wilco_ec_sysfs.c
index 81dded951058..0019d17c0cf9 100644
--- a/drivers/platform/chrome/wilco_ec_sysfs.c
+++ b/drivers/platform/chrome/wilco_ec_sysfs.c
@@ -19,6 +19,7 @@
 #include "wilco_ec_legacy.h"
 #include "wilco_ec_properties.h"
 #include "wilco_ec_adv_power.h"
+#include "wilco_ec_telemetry.h"
 
 #define WILCO_EC_ATTR_RO(_name)						\
 __ATTR(_name, 0444, wilco_ec_##_name##_show, NULL)
@@ -46,7 +47,21 @@ static struct attribute *wilco_ec_toplevel_attrs[] = {
 	NULL
 };
 
-ATTRIBUTE_GROUPS(wilco_ec_toplevel);
+static struct bin_attribute telem_attr = TELEMETRY_BIN_ATTR(telemetry);
+static struct bin_attribute *telem_attrs[] = {
+	&telem_attr,
+	NULL
+};
+
+static const struct attribute_group wilco_ec_toplevel_group = {
+	.attrs = wilco_ec_toplevel_attrs,
+	.bin_attrs = telem_attrs,
+};
+
+static const struct attribute_group *wilco_ec_toplevel_groups[] = {
+	&wilco_ec_toplevel_group,
+	NULL,
+};
 
 /* Make property attributes, which will live inside GOOG000C:00/properties/  */
 
diff --git a/drivers/platform/chrome/wilco_ec_telemetry.c b/drivers/platform/chrome/wilco_ec_telemetry.c
new file mode 100644
index 000000000000..5b8168754b43
--- /dev/null
+++ b/drivers/platform/chrome/wilco_ec_telemetry.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * wilco_ec_legacy - Telemetry sysfs attributes for Wilco EC
+ *
+ * Copyright 2018 Google LLC
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/fs.h>
+#include <linux/kobject.h>
+#include <linux/device.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include "wilco_ec.h"
+#include "wilco_ec_sysfs_util.h"
+
+/* Data buffer for holding EC's response for telemtry data */
+static u8 telemetry_data[EC_MAILBOX_DATA_SIZE_EXTENDED];
+
+ssize_t wilco_ec_telem_write(struct file *filp, struct kobject *kobj,
+			     struct bin_attribute *attr, char *buf, loff_t loff,
+			     size_t count)
+{
+	struct wilco_ec_message msg;
+	int ret;
+	struct device *dev = device_from_kobject(kobj);
+	struct wilco_ec_device *ec = dev_get_drvdata(dev);
+
+	if (count < 1 || count > EC_MAILBOX_DATA_SIZE_EXTENDED)
+		return -EINVAL;
+
+	/* Clear response data buffer */
+	memset(telemetry_data, 0, EC_MAILBOX_DATA_SIZE_EXTENDED);
+
+	msg.type = WILCO_EC_MSG_TELEMETRY;
+	msg.flags = WILCO_EC_FLAG_RAW | WILCO_EC_FLAG_EXTENDED_DATA;
+	msg.command = buf[0];
+	msg.request_data = buf + 1;
+	msg.request_size = EC_MAILBOX_DATA_SIZE;
+	msg.response_data = &telemetry_data;
+	msg.response_size = EC_MAILBOX_DATA_SIZE_EXTENDED;
+
+	/* Send the requested command + data as raw transaction */
+	ret = wilco_ec_mailbox(ec, &msg);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+ssize_t wilco_ec_telem_read(struct file *filp, struct kobject *kobj,
+			    struct bin_attribute *attr, char *buf, loff_t off,
+			    size_t count)
+{
+	memcpy(buf, telemetry_data, min_t(unsigned long, count,
+	       EC_MAILBOX_DATA_SIZE_EXTENDED));
+	return count;
+}
diff --git a/drivers/platform/chrome/wilco_ec_telemetry.h b/drivers/platform/chrome/wilco_ec_telemetry.h
new file mode 100644
index 000000000000..874873284080
--- /dev/null
+++ b/drivers/platform/chrome/wilco_ec_telemetry.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * wilco_ec_telemetry - Telemetry sysfs attributes for Wilco EC
+ *
+ * Copyright 2018 Google LLC
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef WILCO_EC_TELEMETRY_H
+#define WILCO_EC_TELEMETRY_H
+
+#include <linux/fs.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include "wilco_ec.h"
+
+ssize_t wilco_ec_telem_write(struct file *filp, struct kobject *kobj,
+			     struct bin_attribute *attr, char *buf, loff_t loff,
+			     size_t count);
+
+ssize_t wilco_ec_telem_read(struct file *filp, struct kobject *kobj,
+			    struct bin_attribute *attr, char *buf, loff_t off,
+			    size_t count);
+
+#define TELEMETRY_BIN_ATTR(_name) {					\
+	.attr = {.name = __stringify(_name),				\
+		 .mode = VERIFY_OCTAL_PERMISSIONS(0644) },		\
+	.size = EC_MAILBOX_DATA_SIZE_EXTENDED,				\
+	.read = wilco_ec_telem_read,					\
+	.write = wilco_ec_telem_write,					\
+}
+
+#endif /* WILCO_EC_TELEMETRY_H */
-- 
2.20.0.405.gbc1bbc6f85-goog