linux-kernel - Re: [PATCH v4 3/5] serial: sc16is7xx: split into core and I2C/SPI parts (core)

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Date: Tue, 23 Apr 2024 09:14:10 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, peterz@...radead.org,
 mingo@...nel.org, linux-kernel@...r.kernel.org,
 linux-serial@...r.kernel.org, andy.shevchenko@...il.com, Hugo Villeneuve
 <hvilleneuve@...onoff.com>
Subject: Re: [PATCH v4 3/5] serial: sc16is7xx: split into core and I2C/SPI
 parts (core)

On Tue, 23 Apr 2024 12:01:23 +0200
Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> Hi Hugo,
> 
> On Tue, Apr 9, 2024 at 5:48 PM Hugo Villeneuve <hugo@...ovil.com> wrote:
> > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> >
> > Split the common code from sc16is7xx driver and move the I2C and SPI bus
> > parts into interface-specific source files.
> >
> > sc16is7xx becomes the core functions which can support multiple bus
> > interfaces like I2C and SPI.
> >
> > No functional changes intended.
> >
> > Also simplify and improve Kconfig entries.
> >   - Capitalize SPI keyword for consistency
> >   - Display list of supported ICs each on a separate line (and aligned) to
> >     facilitate locating a specific IC model
> >   - Add Manufacturer name at start of description string
> >   - Add UART keyword to description string
> >
> > Suggested-by: Andy Shevchenko <andy.shevchenko@...il.com>
> > Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> 
> Thanks for your patch, which is now commit d49216438139bca0
> ("serial: sc16is7xx: split into core and I2C/SPI parts (core)")
> in tty-next (next-20240415 and later).
> 
> > --- a/drivers/tty/serial/Kconfig
> > +++ b/drivers/tty/serial/Kconfig
> > @@ -1021,41 +1021,30 @@ config SERIAL_SCCNXP_CONSOLE
> >           Support for console on SCCNXP serial ports.
> >
> >  config SERIAL_SC16IS7XX_CORE
> > -       tristate
> > -
> > -config SERIAL_SC16IS7XX
> > -       tristate "SC16IS7xx serial support"
> > +       tristate "NXP SC16IS7xx UART support"
> 
> Hence this replaces SERIAL_SC16IS7XX_CORE by SERIAL_SC16IS7XX,
> so arch/mips/configs/cu1??0-neo_defconfig needs to updated.

Hi Geert,
yes you are right, sorry I missed that.

> 
> >         select SERIAL_CORE
> > -       depends on (SPI_MASTER && !I2C) || I2C
> > +       select SERIAL_SC16IS7XX_SPI if SPI_MASTER
> > +       select SERIAL_SC16IS7XX_I2C if I2C
> 
> So if SPI_MASTER or I2C is enabled, the corresponding SERIAL_SC16IS7XX_*
> subdriver can no longer be disabled?  According to
> https://lore.kernel.org/all/20240403123501.8ef5c99f65a40ca2c10f635a@hugovil.com/
> you did want to support that?

Just to clarify, SPI subdriver will be disabled if
SPI_MASTER is disabled, even if I2C is enabled, and vice versa.

It was not my original intention, V1 of the patch offered the
possibility to enable/disable each subdriver individually, but Andy
pointed out that was maybe not the standard/usual/recommended way of
defining it, and to look into what other subsystems were doing,
especially iio. After some research, I settled on this approach as a
compromise.


Hugo.

> 
> >         help
> > -         This selects support for SC16IS7xx serial ports.
> > -         Supported ICs are SC16IS740, SC16IS741, SC16IS750, SC16IS752,
> > -         SC16IS760 and SC16IS762. Select supported buses using options below.
> > +         Core driver for NXP SC16IS7xx UARTs.
> > +         Supported ICs are:
> > +
> > +           SC16IS740
> > +           SC16IS741
> > +           SC16IS750
> > +           SC16IS752
> > +           SC16IS760
> > +           SC16IS762
> > +
> > +         The driver supports both I2C and SPI interfaces.
> >
> >  config SERIAL_SC16IS7XX_I2C
> > -       bool "SC16IS7xx for I2C interface"
> > -       depends on SERIAL_SC16IS7XX
> > -       depends on I2C
> > -       select SERIAL_SC16IS7XX_CORE if SERIAL_SC16IS7XX
> > -       select REGMAP_I2C if I2C
> > -       default y
> > -       help
> > -         Enable SC16IS7xx driver on I2C bus,
> > -         If required say y, and say n to i2c if not required,
> > -         Enabled by default to support oldconfig.
> > -         You must select at least one bus for the driver to be built.
> > +       tristate
> > +       select REGMAP_I2C
> >
> >  config SERIAL_SC16IS7XX_SPI
> > -       bool "SC16IS7xx for spi interface"
> > -       depends on SERIAL_SC16IS7XX
> > -       depends on SPI_MASTER
> > -       select SERIAL_SC16IS7XX_CORE if SERIAL_SC16IS7XX
> > -       select REGMAP_SPI if SPI_MASTER
> > -       help
> > -         Enable SC16IS7xx driver on SPI bus,
> > -         If required say y, and say n to spi if not required,
> > -         This is additional support to existing driver.
> > -         You must select at least one bus for the driver to be built.
> > +       tristate
> > +       select REGMAP_SPI
> >
> >  config SERIAL_TIMBERDALE
> >         tristate "Support for timberdale UART"
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> -- 
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
>