Re: [PATCH v3 2/2] mailbox: Make mbox_send_message() return error code when tx fails

[Joonwon Kang <joonwonkang@google.com>]

> On Fri, Apr 17, 2026 at 3:43 AM Joonwon Kang <joonwonkang@google.com> wrote:
> >
> > > On Fri, Apr 3, 2026 at 10:19 AM Joonwon Kang <joonwonkang@google.com> wrote:
> > > >
> > > > > On Thu, Apr 2, 2026 at 12:07 PM Joonwon Kang <joonwonkang@google.com> wrote:
> > > > > >
> > > > > > When the mailbox controller failed transmitting message, the error code
> > > > > > was only passed to the client's tx done handler and not to
> > > > > > mbox_send_message(). For this reason, the function could return a false
> > > > > > success. This commit resolves the issue by introducing the tx status and
> > > > > > checking it before mbox_send_message() returns.
> > > > > >
> > > > > Can you please share the scenario when this becomes necessary? This
> > > > > can potentially change the ground underneath some clients, so we have
> > > > > to be sure this is really useful.
> > > >
> > > > I would say the problem here is generic enough to apply to all the cases where
> > > > the send result needs to be checked. Since the return value of the send API is
> > > > not the real send result, any users who believe that this blocking send API
> > > > will return the real send result could fall for that. For example, users may
> > > > think the send was successful even though it was not actually. I believe it is
> > > > uncommon that users have to register a callback solely to get the send result
> > > > even though they are using the blocking send API already. Also, I guess there
> > > > is no special reason why only the mailbox send API should work this way among
> > > > other typical blocking send APIs. For these reasons, this patch makes the send
> > > > API return the real send result. This way, users will not need to register the
> > > > redundant callback and I think the return value will align with their common
> > > > expectation.
> > > >
> > > Clients submit a message into the Mailbox subsystem to be sent out to
> > > the remote side which can happen immediately or later.
> > > If submission fails, clients get immediately notified. If transmission
> > > fails (which is now internal to the subsystem) it is reported to the
> > > client by a callback.
> > > If the API was called mbox_submit_message (which it actually is)
> > > instead of mbox_send_message, there would be no confusion.
> > > We can argue how good/bad the current implementation is, but the fact
> > > is that it is here. And I am reluctant to cause churn without good
> > > reason.
> > > Again, as I said, any, _legal_, setup scenario will help me come over
> > > my reluctance.
> > >
> > > Thanks
> > > Jassi
> >
> > Hi Jassi, can we continue discussing this issue from where we left off last
> > time?
> >
> Long passionate essays are difficult to read, so I haven't yet. A
> simple description of some setup that you think is not supported, will
> keep the discussion focused.
> If your platform is supported but you think the api is not clear,
> updates to the documentation are welcome

Sorry that it was hard for you to read. The long form was to explain what is
misaligned and problematic with data and examples for better understanding
because your previous long essays did not make much sense to me. Please go
through it and let me know if anything is unclear to you. In the mean time, I
will prepare a new version of patch with some update to the API doc.

Thanks,
Joonwon Kang