53 lines
1.5 KiB
C
53 lines
1.5 KiB
C
/*
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* PD Buddy Firmware Library - USB Power Delivery for everyone
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* Copyright 2017-2018 Clayton G. Hobbs
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef PDB_MSG_H
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#define PDB_MSG_H
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#include <stdint.h>
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/*
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* PD message union
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*
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* This can be safely read from or written to in any form without any
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* transformations because everything in the system is little-endian.
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*
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* Two bytes of padding are required at the start to prevent problems due to
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* alignment. Specifically, without the padding, &obj[0] != &bytes[2], making
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* the statement in the previous paragraph invalid.
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*/
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union pd_msg {
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struct {
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uint8_t _pad1[2];
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uint8_t bytes[30];
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} __attribute__((packed));
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struct {
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uint8_t _pad2[2];
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uint16_t hdr;
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union {
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uint32_t obj[7];
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struct {
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uint16_t exthdr;
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uint8_t data[26];
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};
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};
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} __attribute__((packed));
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};
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#endif /* PDB_MSG_H */
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