[PATCH 0/8] membuff: Add tests and update to support a flag for empty/full

[Simon Glass]

Hi Rasmus,

On Tue, 4 Mar 2025 at 11:55, Rasmus Villemoes <ravi at prevas.dk> wrote:
>
> On Tue, Mar 04 2025, Simon Glass <sjg at chromium.org> wrote:
>
> > Hi Rasmus,
> >
> > On Fri, 18 Oct 2024 at 08:55, Simon Glass <sjg at chromium.org> wrote:
> >>
> >> Hi Rasmus,
> >>
> >> On Fri, 18 Oct 2024 at 01:05, Rasmus Villemoes <ravi at prevas.dk> wrote:
> >> >
> >> > On tor, okt 17 2024, Simon Glass <sjg at chromium.org> wrote:
> >> >
> >> > >
> >> > >   membuf: Support a flag for being full
> >> > >
> >> >
> >> > No, that is the worst of all worlds, especially with it being a
> >> > build-time flag. The right implementation is the one where the head and
> >> > tail indices are free-running, where you get such a "flag" for
> >> > free, because you're not wasting the top bits of the indices.
> >> >
> >> > https://www.snellman.net/blog/archive/2016-12-13-ring-buffers/
> >>
> >> >
> >> > If you want to do the churn of renaming anyway, I suggest doing it by
> >> > adding an implementation using the proper scheme under the new name,
> >> > switch users over, and dropping the old. IMO, this series as-is brings
> >> > no value (except for the tests, of course).
> >>
> >> OK. Do you think this series gets us closer to that, or further away?
> >
> > I didn't get a response to this (which is not a problem, I miss things
> > all the time). Anyway I don't like the power-of-two restriction and
> > you can see my other responses above. I've applied this to my tree as
> > I want to have the tests in place.
>
> I stand by my earlier comments that this is the wrong way to implement a
> circular buffer. I hope Tom doesn't pull this.

OK. Are you saying that you think it should only support power-of-two
sizes, or something else? What specifically do you want?

This series:
- adds tests
- renames to membuf
- shows how we could switch to using an empty/full flag instead of
leaving an empty slot, so we can see the code-size image
- does all this without requiring the size to be a power of two (which
limits its usefulness IMO)

Regards,
Simon