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3.1.3 General tag structure

Tags constitutes a buffer of structures following each other padded when necessary in order for each tag to start at 8-bytes aligned address. Tags are terminated by a tag of type ‘0’ and size ‘8’. Every structure has following format:

        +-------------------+
u16     | type              |
u16     | flags             |
u32     | size              |
        +-------------------+

type’ is divided into 2 parts. Lower contains an identifier of contents of the rest of the tag. ‘size’ contains the size of tag including header fields. If bit ‘0’ of ‘flags’ (also known as ‘optional’) is set, the bootloader may ignore this tag if it lacks relevant support. Tags are terminated by a tag of type ‘0’ and size ‘8’.