cros_ec: Handling EC_CMD_GET_NEXT_EVENT

With commit 6900797678 ("cros_ec: Support keyboard scanning with
EC_CMD_GET_NEXT_EVENT") check_for_keys() tries to read keyboard
strokes using EC_CMD_GET_NEXT_EVENT. But the sandbox driver does
not understand this command. We need to reply with
-EC_RES_INVALID_COMMAND to force check_for_keys() to fall back to
use EC_CMD_MKBP_STATE. Currently the driver prints

    ** Unknown EC command 0x67

in this case. With the patch the message is suppressed.

In a future patch we should upgrade the sandbox driver to provide
EC_CMD_GET_NEXT_EVENT support.

Fixes: 6900797678 ("cros_ec: Support keyboard scanning with EC_CMD_GET_NEXT_EVENT")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

drivers/misc/cros_ec_sandbox.c

@@ -460,6 +460,16 @@ static int process_cmd(struct ec_state *ec,
 	case EC_CMD_ENTERING_MODE:
 		len = 0;
 		break;
+	case EC_CMD_GET_NEXT_EVENT:
+		/*
+		 * TODO:
+		 * This driver emulates an old keyboard device supporting
+		 * EC_CMD_MKBP_STATE. Current Chrome OS keyboards use
+		 * EC_CMD_GET_NEXT_EVENT. Cf.
+		 * "mkbp: Add support for buttons and switches"
+		 * https://chromium.googlesource.com/chromiumos/platform/ec/+/87a071941b89e3f7fd3eb329b682e60b3fbd6c73
+		 */
+		return -EC_RES_INVALID_COMMAND;
 	default:
 		printf("   ** Unknown EC command %#02x\n", req_hdr->command);
 		return -1;