On Mon, 2025-09-22 at 15:10 +0200, Nicolas Frattaroli wrote:

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On Monday, 22 September 2025 09:17:27 Central European Summer Time
Jjian Zhou (周建) wrote:

quoted

On Sat, 2025-09-20 at 23:02 -0500, Jassi Brar wrote:

quoted

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On Fri, Sep 19, 2025 at 2:02 PM Nicolas Frattaroli
[off-list ref] wrote:

quoted

On Friday, 19 September 2025 18:32:12 Central European Summer
Time
Jassi Brar wrote:

quoted

On Fri, Sep 19, 2025 at 3:31 AM Chen-Yu Tsai <
wenst@chromium.org>
wrote:

quoted

On Fri, Sep 19, 2025 at 7:50 AM Jassi Brar <
jassisinghbrar@gmail.com> wrote:

quoted

On Thu, Aug 21, 2025 at 9:12 PM Jjian Zhou <
jjian.zhou@mediatek.com> wrote:

.....

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+#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 ?

quoted

+       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-

quoted

con_priv;

Thanks.

An explicit cast would be worse, as at that point you're telling
C to completely ignore any semblance of a type system it has.

     struct mtk_vcp_mbox *priv; 
     priv->dev = dev;
     priv->chans[0].con_priv = priv;
The type of con_priv is "void *". 
Would the conversion mentioned above also have the issue you mentioned?

Thanks.