Re: [PATCH v12 1/7] mfd: Add core driver for Nuvoton NCT6694

Ming Yu
2025-06-12T14:41:07Z

Dear Lee,

Thank you for reviewing,

Lee Jones <lee@kernel.org> 於 2025年6月12日 週四 下午10:00寫道：
>
...
> > +static const struct mfd_cell nct6694_devs[] = {
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 0),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 1),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 2),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 3),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 4),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 5),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 6),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 7),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 8),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 9),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 10),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 11),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 12),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 13),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 14),
> > + MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 15),
> > +
> > + MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 0),
> > + MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 1),
> > + MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 2),
> > + MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 3),
> > + MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 4),
> > + MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 5),
>
> Why have we gone back to this silly numbering scheme?
>
> What happened to using IDA in the child driver?
>

In a previous version, I tried to maintain a static IDA in each
sub-driver. However, I didn’t consider the case where multiple NCT6694
devices are bound to the same driver — in that case, the IDs are not
fixed and become unusable for my purpose.

I’ve since realized that using pdev->id avoids the need for cell->id,
so I reverted to the earlier approach.

That said, do you think it would be a better solution to manage all
the IDAs centrally within the driver? For example:
in nct6694.c
struct nct6694 {
struct device *dev;

struct ida gpio_ida;
struct ida i2c_ida;
struct ida can_ida;
struct ida wdt_ida;
};

static int nct6694_probe(struct platform_device *pdev)
{
ida_init(&nct6694->gpio_ida);
...
}

in gpio-nct6694.c
static int nct6694_gpio_probe(struct platform_device *pdev)
{
id = ida_alloc(&nct6694->gpio_ida, GFP_KERNEL);
}

Best regards,
Ming