A struct/class defined inside a call to a macro won't have its documentation picked up. For example:

/** ... */
PACKED(
struct A {
    /** ... */
    int x;
});

Or even:

PACKED(
/** ... */
struct A {
    /** ... */
    int x;
});

The following configuration I tried didn't help either:
ENABLE_PREPROCESSING = YES
PREDEFINED = PACKED(type)=type
MACRO_EXPANSION = YES

One workaround is to manually mark the documentation comments themselves, i.e. via @class, etc, but this is too tedious and error-prone.

The concrete source code I'm trying to document is this:
- macro: https://github.com/marciof/Eon/blob/master/library/util.h#L207
- struct: https://github.com/marciof/Eon/blob/master/core/architecture/x86/multiboot/Boot_Device.h#L21

This occurs on both Windows 7 64-bit and Kubuntu 10.10 32/64-bit.