[PATCH v10 07/24] mailbox: Add RISC-V SBI message proxy (MPXY) based mailbox driver

[Anup Patel]

Hi Paul,

On Thu, Sep 25, 2025 at 5:57 AM Paul Walmsley <pjw at kernel.org> wrote:
>
> On Mon, 18 Aug 2025, Anup Patel wrote:
>
> > Add a mailbox controller driver for the new SBI message proxy extension
> > which is part of the SBI v3.0 specification.
> > ---
> >  drivers/mailbox/Kconfig               |  11 +
> >  drivers/mailbox/Makefile              |   2 +
> >  drivers/mailbox/riscv-sbi-mpxy-mbox.c | 994 ++++++++++++++++++++++++++
> >  3 files changed, 1007 insertions(+)
> >  create mode 100644 drivers/mailbox/riscv-sbi-mpxy-mbox.c
> >
> > diff --git a/drivers/mailbox/riscv-sbi-mpxy-mbox.c b/drivers/mailbox/riscv-sbi-mpxy-mbox.c
> > new file mode 100644
> > index 000000000000..21404baa6df0
> > --- /dev/null
> > +++ b/drivers/mailbox/riscv-sbi-mpxy-mbox.c
>
> [ ... ]
>
> > +
> > +static int mpxy_mbox_populate_channels(struct mpxy_mbox *mbox)
> > +{
> > +     u32 i, *channel_ids __free(kfree) = NULL;
> > +     struct mpxy_mbox_channel *mchan;
> > +     int rc;
> > +
> > +     /* Find-out of number of channels */
> > +     rc = mpxy_get_channel_count(&mbox->channel_count);
> > +     if (rc)
> > +             return dev_err_probe(mbox->dev, rc, "failed to get number of MPXY channels\n");
> > +     if (!mbox->channel_count)
> > +             return dev_err_probe(mbox->dev, -ENODEV, "no MPXY channels available\n");
> > +
> > +     /* Allocate and fetch all channel IDs */
> > +     channel_ids = kcalloc(mbox->channel_count, sizeof(*channel_ids), GFP_KERNEL);
>
> Should this be devm_kcalloc() ?
>

The usage of channel_ids array is limited only to this function
(mpxy_mbox_populate_channels()) hence we are using scoped
kcalloc() so that channel_ids will be automatically freed when
mpxy_mbox_populate_channels() returns.
(Refer, "__free(kfree)" attribute in the channel_ids declaration)

The scope of memory allocated using devm_kcalloc() is the entire
lifespan of the device which is not needed for channel_ids.

Regards,
Anup