Johannes Berg wrote:

On Fri, 2007-06-29 at 13:51 +0200, Patrick McHardy wrote:

quoted

Do multicast groups have to have a seperate name? Or would it suffice
to have them associated with the genl family and be able to find out
the starting group number? In that case something like

struct genl_mc_groups {
struct genl_family *family or char *family_name or similar;
unsigned int group_off;
unsigned int group_num;
unsigned long groups[];
};

seems to make more sense since you only need a single struct
per family.

Hm. For me that'd work too but Jamal wanted dynamically allocated groups
if I understood him correctly. I'm not too concerned with that case, I'd
think most people know the groups up-front. On the other hand, I can see
something like a group per netdev or whatever other instance too.

Maybe use a mix. Use the bitmap, but allow families to register
multiple of them. In the common case it would only be a single
one, but it would be possible to register groups dynamically.

quoted

Why would you care about holes? If you really want to use sparse
bitmaps that would complicate the code a lot.

No, not sparse bitmaps, but the bitmap could have a hole when a family
goes away, and we could reuse that group number later. If we have it in
a bitmap we know without checking all group IDs.

Right.