linux-kernel - Re: [PATCH v12 0/6] Driver for at91 usart in spi mode

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Message-ID: <20180911093917.GL2494@piout.net>
Date:   Tue, 11 Sep 2018 11:39:17 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Radu Pirea <radu_nicolae.pirea@....ro>, robh+dt@...nel.org,
        mark.rutland@....com, nicolas.ferre@...rochip.com,
        gregkh@...uxfoundation.org, broonie@...nel.org, jslaby@...e.com,
        richard.genoud@...il.com, davem@...emloft.net,
        mchehab+samsung@...nel.org, akpm@...ux-foundation.org,
        arnd@...db.de, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org, linux-spi@...r.kernel.org
Subject: Re: [PATCH v12 0/6] Driver for at91 usart in spi mode

On 11/09/2018 10:33:56+0100, Lee Jones wrote:
> On Tue, 04 Sep 2018, Radu Pirea wrote:
> > Radu Pirea (6):
> >   MAINTAINERS: add at91 usart mfd driver
> >   dt-bindings: add binding for atmel-usart in SPI mode
> >   mfd: at91-usart: added mfd driver for usart
> >   MAINTAINERS: add at91 usart spi driver
> >   spi: at91-usart: add driver for at91-usart as spi
> >   tty/serial: atmel: change the driver to work under at91-usart mfd
> > 
> >  .../bindings/{serial => mfd}/atmel-usart.txt  |  25 +-
> >  MAINTAINERS                                   |  16 +
> >  drivers/mfd/Kconfig                           |   9 +
> >  drivers/mfd/Makefile                          |   1 +
> >  drivers/mfd/at91-usart.c                      |  71 +++
> >  drivers/spi/Kconfig                           |   8 +
> >  drivers/spi/Makefile                          |   1 +
> >  drivers/spi/spi-at91-usart.c                  | 432 ++++++++++++++++++
> >  drivers/tty/serial/Kconfig                    |   1 +
> >  drivers/tty/serial/atmel_serial.c             |  42 +-
> >  include/dt-bindings/mfd/at91-usart.h          |  17 +
> >  11 files changed, 606 insertions(+), 17 deletions(-)
> >  rename Documentation/devicetree/bindings/{serial => mfd}/atmel-usart.txt (76%)
> >  create mode 100644 drivers/mfd/at91-usart.c
> >  create mode 100644 drivers/spi/spi-at91-usart.c
> >  create mode 100644 include/dt-bindings/mfd/at91-usart.h
> 
> Seeing as this patch-set has caused some issues this morning, I took
> the liberty to peruse back into its history to figure out where things
> started to go wrong.  I also re-reviewed the MFD driver - and I'm glad
> I did!
> 
> My Acked-by has been attached to the MFD portion since v5, which is
> why the code hasn't caught my eye before today.  I reviewed the
> relocation of the *binding document* (serial => mfd with no changes)
> in v4 and nothing else.  It appears as though you mistakenly added it
> to the *MFD driver* instead.  This explains my confusion in v10 when I
> told you I'd already reviewed the binding document.
> 
> As I said, I have re-reviewed the MFD driver and I'm afraid to say
> that I do not like what I see.  Besides the missing header file and
> the whitespace tabbing errors, I do not agree with the implementation.
> Using MFD as a shim to hack around driver selection is not a valid
> use-case.
> 
> What's stopping you from just using the compatible string directly to
> select which driver you need to probe?
> 

Then you'd have multiple compatible strings for the same IP which is a
big no-no.


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com