Re: [PATCH v5 2/2] mailbox: mediatek: Add mtk-vcp-mailbox driver

Jassi Brar
2025-09-23T13:17:16Z

On Mon, Sep 22, 2025 at 2:17 AM Jjian Zhou (周建) <Jjian.Zhou@mediatek.com> wrote:
>

> > > > > >
> > > > > > > + void __iomem *base;
> > > > > > > + struct device *dev;
> > > > > > > + struct mbox_controller mbox;
> > > > > > > + const struct mtk_vcp_mbox_cfg *cfg;
> > > > > > > + struct mtk_ipi_info ipi_recv;
> > > > > >
> > > > > > Maybe also have "struct mbox_chan chan[1]; " so that you
> > > > > > don't have to
> > > > > > allocate one during the probe.
> > > > > > Also if you have "struct mbox_controller mbox;" as the first
> > > > > > member,
> > > > > > you could simply typecast that to get this structure.
> > > > > > Something like "struct mpfs_mbox" in mailbox-mpfs.c
> > > > >
> > > > > I read somewhere that this way of subclassing is not
> > > > > recommended.
> > > > > Instead the base class should explicitly not be the first
> > > > > member.
> > > > > And then container_of() should be used.
> > > > >
> > > > > I don't remember where I read this though. But I think the
> > > > > explicit
> > > > > container_of() is easier for understanding the intent.
> > > > >
> > > >
> > > > And how does container_of() work ? :)
> > > > typcasting the first member to its parent is the simplest form of
> > > > container_of.
> > > >
> > > > -j
> > > >
> > > >
> > >
> > > Which is why it's completely equivalent and since code is supposed
> > > to communicate meaning to humans, container_of should be used.
> > >
> >
> > Nobody is suggesting typecasting cfg, dev or anything else.
> > Typecasting between mailbox controllers is fine and arguably easier
> > on
> > the eyes than using a container_of.
> >
> > -j
>
> OK. How about:
> struct mtk_vcp_mbox *priv = (struct mtk_vcp_mbox *)chan->con_priv;
>
You don't need to typecast a void *. So simply do
struct mtk_vcp_mbox *priv = chan->con_priv;