platform/chrome: cros_ec_sysfs: Modify error handling

When accessing a sysfs attribute, if the EC command fails, -EPROTO is
now returned instead of an error message as it is unlikely an app is
parsing the error message to do something meaningful.
Also, this patch makes use of cros_ec_cmd_xfer_status() instead of
cros_ec_cmd_xfer() so an error message is printed in the syslog.
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Benson Leung <bleung@chromium.org>

drivers/platform/chrome/cros_ec_sysfs.c

@@ -114,15 +114,9 @@ static ssize_t store_ec_reboot(struct device *dev,
 	msg->command = EC_CMD_REBOOT_EC + ec->cmd_offset;
 	msg->outsize = sizeof(*param);
 	msg->insize = 0;
-	ret = cros_ec_cmd_xfer(ec->ec_dev, msg);
-	if (ret < 0) {
+	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
+	if (ret < 0)
 		count = ret;
-		goto exit;
-	}
-	if (msg->result != EC_RES_SUCCESS) {
-		dev_dbg(ec->dev, "EC result %d\n", msg->result);
-		count = -EINVAL;
-	}
 exit:
 	kfree(msg);
 	return count;
@@ -150,17 +144,11 @@ static ssize_t show_ec_version(struct device *dev,
 	msg->command = EC_CMD_GET_VERSION + ec->cmd_offset;
 	msg->insize = sizeof(*r_ver);
 	msg->outsize = 0;
-	ret = cros_ec_cmd_xfer(ec->ec_dev, msg);
+	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
 	if (ret < 0) {
 		count = ret;
 		goto exit;
 	}
-	if (msg->result != EC_RES_SUCCESS) {
-		count = scnprintf(buf, PAGE_SIZE,
-				  "ERROR: EC returned %d\n", msg->result);
-		goto exit;
-	}
-
 	r_ver = (struct ec_response_get_version *)msg->data;
 	/* Strings should be null-terminated, but let's be sure. */
 	r_ver->version_string_ro[sizeof(r_ver->version_string_ro) - 1] = '\0';
@@ -255,14 +243,9 @@ static ssize_t show_ec_flashinfo(struct device *dev,
 	msg->command = EC_CMD_FLASH_INFO + ec->cmd_offset;
 	msg->insize = sizeof(*resp);
 	msg->outsize = 0;
-	ret = cros_ec_cmd_xfer(ec->ec_dev, msg);
+	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
 	if (ret < 0)
 		goto exit;
-	if (msg->result != EC_RES_SUCCESS) {
-		ret = scnprintf(buf, PAGE_SIZE,
-				"ERROR: EC returned %d\n", msg->result);
-		goto exit;
-	}
 
 	resp = (struct ec_response_flash_info *)msg->data;