linux-kernel - Re: [PATCH v3] mfd: ch341: add driver for the WCH CH341 in I2C/GPIO mode

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Date:   Tue, 15 Mar 2022 14:58:51 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     frank zago <frank@...o.net>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Jan-Niklas Burfeind <kernel@...ionpri.me>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Wolfram Sang <wsa@...nel.org>, Johan Hovold <johan@...nel.org>,
        linux-usb@...r.kernel.org, gunar@...orcht.net
Subject: Re: [PATCH v3] mfd: ch341: add driver for the WCH CH341 in I2C/GPIO
 mode

On Sun, 13 Mar 2022, frank zago wrote:

> The CH341 is a multifunction chip, presenting 3 different USB PID. One
> of these functions is for I2C/SPI/GPIO. This new driver manages I2C
> and GPIO.
> 
> The I2C interface can run at 4 different speeds. This driver currently
> only offer 100MHz. Tested with a variety of I2C sensors, and the IIO
> subsystem.
> 
> The GPIO interface offers 16 GPIOs. 6 are read/write, and 10 are
> read-only.
> 
> Signed-off-by: frank zago <frank@...o.net>
> ---
> 
> Changes from v2:
>   - bug fixes
>   - more robust USB enumeration
>   - Changed to an MFD driver as suggested

Perhaps you should have engaged with me before potentially wasting
your valuable time.

MFD is designed to take a parent platform driver and split it out into
various sub-systems.  If you don't use the MFD Core API (which is the
case here) it is not an MFD.  MFD is not a dumping ground for
collections of random device drivers.

I have no problem with you placing registration and core code inside
MFD (that *is* what it was designed for), but the leaf 'functionality'
should be placed in more appropriate locations.

I2C  => drivers/i2c
SPI  => drivers/spi
GPIO => drivers/gpio (or perhaps drivers/pinctrl)
USB  => drivers/usb
UART => drivers/tty/serial

Etc ... Find places for everything.

Anything left over, give to Greg (drivers/misc). :)

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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