soc: qcom: Introduce QMI encoder/decoder

Add the helper library for encoding and decoding QMI encoded messages.
The implementation is taken from lib/qmi_encdec.c of the Qualcomm kernel
(msm-3.18).

Modifications has been made to the public API, source buffers has been
made const and the debug-logging part was omitted, for now.

Acked-by: Chris Lew <clew@codeaurora.org>
Tested-by: Chris Lew <clew@codeaurora.org>
Tested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

include/linux/soc/qcom/qmi.h

@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2012-2014, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2017, Linaro Ltd.
+ */
+#ifndef __QMI_HELPERS_H__
+#define __QMI_HELPERS_H__
+
+#include <linux/types.h>
+
+/**
+ * qmi_header - wireformat header of QMI messages
+ * @type:	type of message
+ * @txn_id:	transaction id
+ * @msg_id:	message id
+ * @msg_len:	length of message payload following header
+ */
+struct qmi_header {
+	u8 type;
+	u16 txn_id;
+	u16 msg_id;
+	u16 msg_len;
+} __packed;
+
+#define QMI_REQUEST	0
+#define QMI_RESPONSE	2
+#define QMI_INDICATION	4
+
+#define QMI_COMMON_TLV_TYPE 0
+
+enum qmi_elem_type {
+	QMI_EOTI,
+	QMI_OPT_FLAG,
+	QMI_DATA_LEN,
+	QMI_UNSIGNED_1_BYTE,
+	QMI_UNSIGNED_2_BYTE,
+	QMI_UNSIGNED_4_BYTE,
+	QMI_UNSIGNED_8_BYTE,
+	QMI_SIGNED_2_BYTE_ENUM,
+	QMI_SIGNED_4_BYTE_ENUM,
+	QMI_STRUCT,
+	QMI_STRING,
+};
+
+enum qmi_array_type {
+	NO_ARRAY,
+	STATIC_ARRAY,
+	VAR_LEN_ARRAY,
+};
+
+/**
+ * struct qmi_elem_info - describes how to encode a single QMI element
+ * @data_type:	Data type of this element.
+ * @elem_len:	Array length of this element, if an array.
+ * @elem_size:	Size of a single instance of this data type.
+ * @array_type:	Array type of this element.
+ * @tlv_type:	QMI message specific type to identify which element
+ *		is present in an incoming message.
+ * @offset:	Specifies the offset of the first instance of this
+ *		element in the data structure.
+ * @ei_array:	Null-terminated array of @qmi_elem_info to describe nested
+ *		structures.
+ */
+struct qmi_elem_info {
+	enum qmi_elem_type data_type;
+	u32 elem_len;
+	u32 elem_size;
+	enum qmi_array_type array_type;
+	u8 tlv_type;
+	u32 offset;
+	struct qmi_elem_info *ei_array;
+};
+
+#define QMI_RESULT_SUCCESS_V01			0
+#define QMI_RESULT_FAILURE_V01			1
+
+#define QMI_ERR_NONE_V01			0
+#define QMI_ERR_MALFORMED_MSG_V01		1
+#define QMI_ERR_NO_MEMORY_V01			2
+#define QMI_ERR_INTERNAL_V01			3
+#define QMI_ERR_CLIENT_IDS_EXHAUSTED_V01	5
+#define QMI_ERR_INVALID_ID_V01			41
+#define QMI_ERR_ENCODING_V01			58
+#define QMI_ERR_INCOMPATIBLE_STATE_V01		90
+#define QMI_ERR_NOT_SUPPORTED_V01		94
+
+/**
+ * qmi_response_type_v01 - common response header (decoded)
+ * @result:	result of the transaction
+ * @error:	error value, when @result is QMI_RESULT_FAILURE_V01
+ */
+struct qmi_response_type_v01 {
+	u16 result;
+	u16 error;
+};
+
+extern struct qmi_elem_info qmi_response_type_v01_ei[];
+
+void *qmi_encode_message(int type, unsigned int msg_id, size_t *len,
+			 unsigned int txn_id, struct qmi_elem_info *ei,
+			 const void *c_struct);
+
+int qmi_decode_message(const void *buf, size_t len,
+		       struct qmi_elem_info *ei, void *c_struct);
+
+#endif