Multiboot 2 Header Tags: How many and in what sequence?

Multiboot 2 Header Tags: How many and in what sequence?

[Hans Ulrich Niedermann]

The Multiboot2 specification specifies a number of header tags which an
OS image can define and which the bootloader needs to parse.

However, the spec does not mention in which order an OS image should
contain MB2 header tags:

  * Ascending numerical order of the 'type' value? (This could only
    happen if you discount the type=0 termination tag.)

  * The order from the specification?

  * No order at all?

Also, there is no mention of whether MB2 header tags are permitted to
appear multiple times in the OS image. Reasonable use cases could be:

  * Two Information Request tags, one with the values the OS image
    absolutely requires which has the optional bit cleared, and one
    with values the OS image would like to know but does not really
    need and which does have the optional bit set.

  * Multiple "framebuffer tags" requesting multiple graphics modes in
    e.g. descending order or preference.

Does anyone have any insights into this?

Uli