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

[Lee Jones <lee@kernel.org>]

On Thu, 12 Jun 2025, Ming Yu wrote:

> 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.

Not sure I understand.

> 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);
> }

No that would be way worse.

-- 
Lee Jones [李琼斯]