platform/chrome: wilco_ec: Add version sysfs entries

Add the ability to extract version information from the EC.

Example Output:
$ cd /sys/bus/platform/devices/GOOG000C:00
$ tail build_date build_revision version model_number
==> build_date <==
04/25/19

==> build_revision <==
d2592cae0

==> version <==
00.00.14

==> model_number <==
08B6

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-by: Nick Crews <ncrews@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

drivers/platform/chrome/wilco_ec/sysfs.c

@@ -23,6 +23,25 @@ struct boot_on_ac_request {
 	u8 reserved7;
 } __packed;
 
+#define CMD_EC_INFO			0x38
+enum get_ec_info_op {
+	CMD_GET_EC_LABEL	= 0,
+	CMD_GET_EC_REV		= 1,
+	CMD_GET_EC_MODEL	= 2,
+	CMD_GET_EC_BUILD_DATE	= 3,
+};
+
+struct get_ec_info_req {
+	u8 cmd;			/* Always CMD_EC_INFO */
+	u8 reserved;
+	u8 op;			/* One of enum get_ec_info_op */
+} __packed;
+
+struct get_ec_info_resp {
+	u8 reserved[2];
+	char value[9]; /* __nonstring: might not be null terminated */
+} __packed;
+
 static ssize_t boot_on_ac_store(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t count)
@@ -57,8 +76,68 @@ static ssize_t boot_on_ac_store(struct device *dev,
 
 static DEVICE_ATTR_WO(boot_on_ac);
 
+static ssize_t get_info(struct device *dev, char *buf, enum get_ec_info_op op)
+{
+	struct wilco_ec_device *ec = dev_get_drvdata(dev);
+	struct get_ec_info_req req = { .cmd = CMD_EC_INFO, .op = op };
+	struct get_ec_info_resp resp;
+	int ret;
+
+	struct wilco_ec_message msg = {
+		.type = WILCO_EC_MSG_LEGACY,
+		.request_data = &req,
+		.request_size = sizeof(req),
+		.response_data = &resp,
+		.response_size = sizeof(resp),
+	};
+
+	ret = wilco_ec_mailbox(ec, &msg);
+	if (ret < 0)
+		return ret;
+
+	return scnprintf(buf, PAGE_SIZE, "%.*s\n", (int)sizeof(resp.value),
+			 (char *)&resp.value);
+}
+
+static ssize_t version_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	return get_info(dev, buf, CMD_GET_EC_LABEL);
+}
+
+static DEVICE_ATTR_RO(version);
+
+static ssize_t build_revision_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	return get_info(dev, buf, CMD_GET_EC_REV);
+}
+
+static DEVICE_ATTR_RO(build_revision);
+
+static ssize_t build_date_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	return get_info(dev, buf, CMD_GET_EC_BUILD_DATE);
+}
+
+static DEVICE_ATTR_RO(build_date);
+
+static ssize_t model_number_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	return get_info(dev, buf, CMD_GET_EC_MODEL);
+}
+
+static DEVICE_ATTR_RO(model_number);
+
+
 static struct attribute *wilco_dev_attrs[] = {
 	&dev_attr_boot_on_ac.attr,
+	&dev_attr_build_date.attr,
+	&dev_attr_build_revision.attr,
+	&dev_attr_model_number.attr,
+	&dev_attr_version.attr,
 	NULL,
 };