On Thu, Sep 11, 2014 at 12:49:22PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Sep 11, 2014 at 05:35:27PM +0200, Jiri Olsa escreveu:
> > On Thu, Sep 11, 2014 at 12:23:30PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Thu, Sep 11, 2014 at 04:59:45PM +0200, Jiri Olsa escreveu:
> > > > On Thu, Sep 11, 2014 at 10:29:11AM -0300, Arnaldo Carvalho de Melo
> > > > wrote:
> > > > > But then I had no use whatsoever for the ->ptr one at this point, so I
> > > > > just nuked it, to keep _just_ what is used _right now_, and added the
> > > > > comment to the changelog :-)
>
> > > > if we are treeting tools/lib/api as 'external' lib, I think we should
> > > > use 'void *' for priv and let the user retype it to whatever he wants
>
> > > > but I dont care/insist here too much.. it just seems strange to me ;-)
> > >
> > > Ok, so perhaps it should be:
> > >
> > > struct fdarray {
> > > ...
> > > union {
> > > int idx;
> > > } *priv;
> > > ...
> > > }
> > >
> > > And then perf's evlist will use:
> > >
> > > fda->priv[fd].idx;
> > >
> > > Then, when we get the need for a pointer, we can go there and
> > > add it to the union.
> > >
> > > This will make tools/lib/api/fd/ a little bit more friendly to
> > > use outside the kernel sources, since then a new version will be source
> > > code compatible (but not necessarily binary compatible).
> >
> > you lost me ;-)
> >
> > could you please make an example of the !compatibility you mentioned?
>
> If I leave it as is now, when I add that void * pointer to each entry in
> fdarray->priv[], I will have to change fdarray's users, i.e. right now I
> will have to go and change evlist.h, i.e. every place that has:
>
> fda->priv[fd];
>
> will have to be changed to:
>
> fda->priv[fd].idx;
>
> If I instead change it to:
>
> struct fdarray {
> ...
> union {
> int idx;
> } *priv;
> ...
> }
>
> Then I will not have to change anything when I add that void * pointer
> to the union.
I dont think there's any trouble like that if you keep
just void* priv pointer and let users to store there
whatever they like
>
> > > If we commit to that we can't just go on and change all its
> > > users as we can now do for things like 'struct sk_buff', 'struct sock'
> > > and any other kernel data structures.
> > > There are costs in making it 'external' in the sense you're
> > > implying. I want to make it a bit less 'external' (in your sense), at
> > > least while we initially implement new stuff like this one.
>
> > and the costs?
>
> > also I did not mean that union above, what I meant was:
>
> > struct fdarray {
> > ...
> > void *priv;
> > ...
> > }
>
> Yeah, that is what I am trying to avoid. This will make it use
> sizeof(void *) for each entry, and I have no use for that right now. All
> I need is sizeof(int) for each entry.
hm? but you're using pointer (int*) not int .. size will be sizeof(unsigned
long) anyway
jirka
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