platform/chrome: cros_ec_proto: return 0 on getting cmd mask success

cros_ec_get_host_command_version_mask() used to return value from
send_command() which is number of available bytes for input payload on
success (i.e. sizeof(struct ec_response_get_cmd_versions)).

However, the callers don't need to know how many bytes are available.

Don't return number of available bytes.  Instead, return 0 on success;
otherwise, negative integers on error.

Also remove the unneeded `ver_mask` initialization as the callers should
take it only if cros_ec_get_host_command_version_mask() returns 0.
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220609084957.3684698-15-tzungbi@kernel.org

drivers/platform/chrome/cros_ec_proto.c

@@ -453,6 +453,7 @@ static int cros_ec_get_host_command_version_mask(struct cros_ec_device *ec_dev,
 	if (ret > 0) {
 		rver = (struct ec_response_get_cmd_versions *)msg->data;
 		*mask = rver->version_mask;
+		ret = 0;
 	}
 
 	kfree(msg);
@@ -470,7 +471,7 @@ static int cros_ec_get_host_command_version_mask(struct cros_ec_device *ec_dev,
 int cros_ec_query_all(struct cros_ec_device *ec_dev)
 {
 	struct device *dev = ec_dev->dev;
-	u32 ver_mask = 0;
+	u32 ver_mask;
 	int ret;
 
 	/* First try sending with proto v3. */
@@ -509,9 +510,7 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
 	}
 
 	/* Probe if MKBP event is supported */
-	ret = cros_ec_get_host_command_version_mask(ec_dev,
-						    EC_CMD_GET_NEXT_EVENT,
-						    &ver_mask);
+	ret = cros_ec_get_host_command_version_mask(ec_dev, EC_CMD_GET_NEXT_EVENT, &ver_mask);
 	if (ret < 0 || ver_mask == 0) {
 		ec_dev->mkbp_event_supported = 0;
 	} else {
@@ -521,10 +520,8 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
 	}
 
 	/* Probe if host sleep v1 is supported for S0ix failure detection. */
-	ret = cros_ec_get_host_command_version_mask(ec_dev,
-						    EC_CMD_HOST_SLEEP_EVENT,
-						    &ver_mask);
-	ec_dev->host_sleep_v1 = (ret >= 0 && (ver_mask & EC_VER_MASK(1)));
+	ret = cros_ec_get_host_command_version_mask(ec_dev, EC_CMD_HOST_SLEEP_EVENT, &ver_mask);
+	ec_dev->host_sleep_v1 = (ret == 0 && (ver_mask & EC_VER_MASK(1)));
 
 	/* Get host event wake mask. */
 	ret = cros_ec_get_host_event_wake_mask(ec_dev, &ec_dev->host_event_wake_mask);