Re: [PATCH net-next v4 5/8] mfd: zl3073x: Add functions to work with register mailboxes

[Ivan Vecera]

On 25. 04. 25 12:17 odp., Lee Jones wrote:
> On Fri, 25 Apr 2025, Ivan Vecera wrote:
>
> > On 25. 04. 25 8:55 dop., Lee Jones wrote:
> > > On Thu, 24 Apr 2025, Ivan Vecera wrote:
> > >
> > > > On 24. 04. 25 9:29 odp., Andrew Lunn wrote:
> > > > > > Yes, PHC (PTP) sub-driver is using mailboxes as well. Gpio as well for some
> > > > > > initial configuration.
> > > > >
> > > > > O.K, so the mailbox code needs sharing. The question is, where do you
> > > > > put it.
> > > >
> > > > This is crucial question... If I put the MB API into DPLL sub-driver
> > > > then PTP sub-driver will depend on it. Potential GPIO sub-driver as
> > > > well.
> > > >
> > > > There could be some special library module to provide this for
> > > > sub-drivers but is this what we want? And if so where to put it?
> > >
> > > MFD is designed to take potentially large, monolithic devices and split
> > > them up into smaller, more organised chunks, then Linusify them.  This
> > > way, area experts (subsystem maintainers) get to concern themselves only
> > > with the remit to which they are most specialised / knowledgable.  MFD
> > > will handle how each of these areas are divided up and create all of the
> > > shared resources for them.  On the odd occasion it will also provide a
> > > _small_ API that the children can use to talk to the parent device.
> > >
> > > However .... some devices, like yours, demand an API which is too
> > > complex to reside in the MFD subsystem itself.  This is not the first
> > > time this has happened and I doubt it will be the last.  My first
> > > recommendation is usually to place all of the comms in drivers/platform,
> > > since, at least in my own mind, if a complex API is required, then the
> > > device has become almost platform-like.  There are lots of examples of
> > > H/W comm APIs in there already for you to peruse.
> >
> > OK, I will do it differently... Will drop MB API at all from MFD and
> > just expose the additional mutex from MFD for multi-op access.
> > Mailboxes will be handled directly by sub-devices.
> >
> > Short description:
> > MFD exposes:
> > zl3073x_{read,write}_u{8,16,32,48}() & zl3073x_poll_u8()
> > - to read/write/poll registers
> > - they checks that multiop_lock is taken when caller is accessing
> >    registers from Page 10 and above
> >
> > zl3073x_multiop_{lock,unlock}()
> > - to protect operation where multiple reads, writes and poll is required
> >    to be done atomically

Or maybe just define zl3073x_dev.multiop_lock and allow callers to use

guard(mutex)(zldev->multiop_lock)
--or--
scoped_guard(mutex)(zldev_multiop_lock) {
...
}

> Looks sensible.  If this is aligned with the discussions that have been
> taking place between you and Andrew.  Let's see the code before we make
> any binding agreements.  =:)