Message-ID: <20250502080754.GD3865826@google.com>
Date: Fri, 2 May 2025 09:07:54 +0100
From: Lee Jones <lee@...nel.org>
To: Ming Yu <a0282524688@...il.com>
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 v10 1/7] mfd: Add core driver for Nuvoton NCT6694

On Fri, 02 May 2025, Ming Yu wrote:

> Dear Lee,
> 
> Thank you for your review. I have a few questions and would appreciate
> your advice.
> 
> Lee Jones <lee@...nel.org> 於 2025年5月1日 週四 下午8:22寫道：
> >
> > On Wed, 23 Apr 2025, a0282524688@...il.com wrote:
> >
> > > From: Ming Yu <tmyu0@...oton.com>
> > >
> > > The Nuvoton NCT6694 provides an USB interface to the host to
> > > access its features.
> > >
> > > Sub-devices can use the USB functions nct6694_read_msg() and
> > > nct6694_write_msg() to issue a command. They can also request
> > > interrupt that will be called when the USB device receives its
> > > interrupt pipe.
> > >
> > > Signed-off-by: Ming Yu <tmyu0@...oton.com>
> > > ---
> >
> > v10 and no change log?  Please add a change log.
> >
> 
> The change log is currently available at
> https://patchwork.ozlabs.org/project/rtc-linux/cover/20250423094058.1656204-1-tmyu0@nuvoton.com/
> I will move the relevant entries into each individual patch in the
> next revision.
> 
> > >  MAINTAINERS                 |   6 +
> > >  drivers/mfd/Kconfig         |  15 ++
> > >  drivers/mfd/Makefile        |   2 +
> > >  drivers/mfd/nct6694.c       | 387 ++++++++++++++++++++++++++++++++++++
> > >  include/linux/mfd/nct6694.h | 101 ++++++++++
> > >  5 files changed, 511 insertions(+)
> > >  create mode 100644 drivers/mfd/nct6694.c
> > >  create mode 100644 include/linux/mfd/nct6694.h
> > >
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index fa1e04e87d1d..b2dfcc063f88 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -17358,6 +17358,12 @@ F:   drivers/nubus/
> > >  F:   include/linux/nubus.h
> > >  F:   include/uapi/linux/nubus.h
> > >
> > > +NUVOTON NCT6694 MFD DRIVER
> > > +M:   Ming Yu <tmyu0@...oton.com>
> > > +S:   Supported
> > > +F:   drivers/mfd/nct6694.c
> > > +F:   include/linux/mfd/nct6694.h
> > > +
> > >  NVIDIA (rivafb and nvidiafb) FRAMEBUFFER DRIVER
> > >  M:   Antonino Daplas <adaplas@...il.com>
> > >  L:   linux-fbdev@...r.kernel.org
> > > diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> > > index 22b936310039..cd4d826a7fcb 100644
> > > --- a/drivers/mfd/Kconfig
> > > +++ b/drivers/mfd/Kconfig
> > > @@ -1058,6 +1058,21 @@ config MFD_MENF21BMC
> > >         This driver can also be built as a module. If so the module
> > >         will be called menf21bmc.
> > >
> > > +config MFD_NCT6694
> > > +     tristate "Nuvoton NCT6694 support"
> > > +     select MFD_CORE
> > > +     depends on USB
> > > +     help
> > > +       This enables support for the Nuvoton USB device NCT6694, which shares
> > > +       peripherals.
> > > +       The Nuvoton NCT6694 is a peripheral expander with 16 GPIO chips,
> > > +       6 I2C controllers, 2 CANfd controllers, 2 Watchdog timers, ADC,
> > > +       PWM, and RTC.
> > > +       This driver provides core APIs to access the NCT6694 hardware
> > > +       monitoring and control features.
> > > +       Additional drivers must be enabled to utilize the specific
> > > +       functionalities of the device.
> > > +
> > >  config MFD_OCELOT
> > >       tristate "Microsemi Ocelot External Control Support"
> > >       depends on SPI_MASTER
> > > diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> > > index 948cbdf42a18..471dc1f183b8 100644
> > > --- a/drivers/mfd/Makefile
> > > +++ b/drivers/mfd/Makefile
> > > @@ -120,6 +120,8 @@ obj-$(CONFIG_MFD_MC13XXX) += mc13xxx-core.o
> > >  obj-$(CONFIG_MFD_MC13XXX_SPI)        += mc13xxx-spi.o
> > >  obj-$(CONFIG_MFD_MC13XXX_I2C)        += mc13xxx-i2c.o
> > >
> > > +obj-$(CONFIG_MFD_NCT6694)    += nct6694.o
> > > +
> > >  obj-$(CONFIG_MFD_CORE)               += mfd-core.o
> > >
> > >  ocelot-soc-objs                      := ocelot-core.o ocelot-spi.o
> > > diff --git a/drivers/mfd/nct6694.c b/drivers/mfd/nct6694.c
> > > new file mode 100644
> > > index 000000000000..2480ca56f350
> > > --- /dev/null
> > > +++ b/drivers/mfd/nct6694.c
> > > @@ -0,0 +1,387 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Copyright (C) 2024 Nuvoton Technology Corp.
> > > + *
> > > + * Nuvoton NCT6694 core driver using USB interface to provide
> > > + * access to the NCT6694 hardware monitoring and control features.
> > > + *
> > > + * The NCT6694 is an integrated controller that provides GPIO, I2C,
> > > + * CAN, WDT, HWMON and RTC management.
> > > + *
> >
> > Superfluous blank line.
> >
> 
> Remove it in v11.
> 
> > > + */
> > > +
> > > +#include <linux/bits.h>
> > > +#include <linux/interrupt.h>
> > > +#include <linux/irq.h>
> > > +#include <linux/irqdomain.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/mfd/core.h>
> > > +#include <linux/mfd/nct6694.h>
> > > +#include <linux/module.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/usb.h>
> > > +
> > > +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),
> >
> > These are all identical.
> >
> > I thought you were going to use PLATFORM_DEVID_AUTO?  In fact, you are
> > already using PLATFORM_DEVID_AUTO since you are calling
> > mfd_add_hotplug_devices().  So you don't need this IDs.
> >
> > MFD_CELL_NAME() should do.
> >
> 
> Yes, it uses PLATFORM_DEVID_AUTO, but in my implementation, the
> sub-devices use cell->id instead of platform_device->id, so it doesn't
> affect the current behavior.
> However, if you think there's a better approach or that this should be
> changed for consistency or correctness, I'm happy to update it, please
> let me know your recommendation.
> 
> When using MFD_CELL_NAME(), the platform_device->id for the GPIO
> devices is assigned values from 1 to 16, and for the I2C devices from
> 1 to 6, but I need the ID offset to start from 0 instead.

Oh no, don't do that.  mfd_cell isn't supposed to be used outside of MFD.

Just use the platform_device id-- if you really need to start from 0.

As an aside, I'm surprised numbering starts from 1.

-- 
Lee Jones [李琼斯]

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