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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOoeyxV-E_HQOBu0Pzfy0b0yJ2qbrW_C8pATCTWE4+PXqvHL6g@mail.gmail.com>
Date: Fri, 13 Jun 2025 09:54:56 +0800
From: Ming Yu <a0282524688@...il.com>
To: Lee Jones <lee@...nel.org>
Cc: linus.walleij@...aro.org, brgl@...ev.pl, andi.shyti@...nel.org, 
	mkl@...gutronix.de, mailhol.vincent@...adoo.fr, andrew+netdev@...n.ch, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	wim@...ux-watchdog.org, linux@...ck-us.net, jdelvare@...e.com, 
	alexandre.belloni@...tlin.com, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org, 
	linux-can@...r.kernel.org, netdev@...r.kernel.org, 
	linux-watchdog@...r.kernel.org, linux-hwmon@...r.kernel.org, 
	linux-rtc@...r.kernel.org, linux-usb@...r.kernel.org, 
	Ming Yu <tmyu0@...oton.com>
Subject: Re: [PATCH v12 1/7] mfd: Add core driver for Nuvoton NCT6694

Lee Jones <lee@...nel.org> 於 2025年6月12日 週四 下午11:23寫道：
>
> On Thu, 12 Jun 2025, Ming Yu wrote:
>
> > Dear Lee,
> >
> > Thank you for reviewing,
> >
> > Lee Jones <lee@...nel.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.
>

As far as I know, if I maintain the IDA in the sub-drivers and use
multiple MFD_CELL_NAME("nct6694-gpio") entries in the MFD, the first
NCT6694 device bound to the GPIO driver will receive IDs 0~15.
However, when a second NCT6694 device is connected to the system, it
will receive IDs 16~31.
Because of this behavior, I switched back to using platform_device->id.

> > 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.
>


Thanks,
Ming