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

Nicolas Frattaroli
2025-09-19T19:02:30Z

On Friday, 19 September 2025 18:32:12 Central European Summer Time Jassi Brar wrote:
> On Fri, Sep 19, 2025 at 3:31 AM Chen-Yu Tsai <wenst@chromium.org> wrote:
> >
> > On Fri, Sep 19, 2025 at 7:50 AM Jassi Brar <jassisinghbrar@gmail.com> wrote:
> > >
> > > On Thu, Aug 21, 2025 at 9:12 PM Jjian Zhou <jjian.zhou@mediatek.com> wrote:
> > >
> > > .....
> > >
> > > > +#include <linux/module.h>
> > > > +#include <linux/of.h>
> > > > +#include <linux/platform_device.h>
> > > > +#include <linux/slab.h>
> > > > +
> > > > +struct mtk_vcp_mbox_priv {
> > > Maybe 'mtk_vcp_mbox' is a more appropriate name ?
> > >
> > > > + 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.

"In this case if nobody ever reorders members you can avoid a
preprocessor macro that will get optimised away" is pointless
nitpicking. It's a strictly worse way to do the same thing.

Why bikeshed the use of container_of of all things?