ASoC: Intel: Skylake: Add strip extended manifest utility

Some upcoming platforms like broxton etc have extended manifest
in firmware binary. This is not required to be downloaded to DSP.
So driver needs to strip this before downloading.

Add a utility function to check if a header exists, and remove it
in that case

Signed-off-by: Ramesh Babu <ramesh.babu@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/skylake/skl-sst-utils.c

@@ -0,0 +1,54 @@
+/*
+ *  skl-sst-utils.c - SKL sst utils functions
+ *
+ *  Copyright (C) 2016 Intel Corp
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as version 2, as
+ * published by the Free Software Foundation.
+ *
+ * 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/firmware.h>
+#include "skl-sst-dsp.h"
+
+/* FW Extended Manifest Header id = $AE1 */
+#define SKL_EXT_MANIFEST_HEADER_MAGIC   0x31454124
+
+struct skl_ext_manifest_hdr {
+	u32 id;
+	u32 len;
+	u16 version_major;
+	u16 version_minor;
+	u32 entries;
+};
+
+/*
+ * some firmware binary contains some extended manifest. This needs
+ * to be stripped in that case before we load and use that image.
+ *
+ * So check for magic header, if found strip the header
+ */
+int skl_dsp_strip_extended_manifest(struct firmware *fw)
+{
+	struct skl_ext_manifest_hdr *hdr;
+
+	/* check if fw file is greater than header we are looking */
+	if (fw->size < sizeof(hdr)) {
+		pr_err("%s: Firmware file small, no hdr\n", __func__);
+		return -EINVAL;
+	}
+
+	hdr = (struct skl_ext_manifest_hdr *)fw->data;
+
+	if (hdr->id == SKL_EXT_MANIFEST_HEADER_MAGIC) {
+		fw->size -= hdr->len;
+		fw->data += hdr->len;
+	}
+
+	return 0;
+}