linux-kernel - Re: [PATCH] i2c: i801: add I2C

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Message-ID: <a24a2a8a-2be9-414d-8378-668ba4408c71@roeck-us.net>
Date: Mon, 8 Apr 2024 04:42:10 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Arnd Bergmann <arnd@...db.de>
Cc: Arnd Bergmann <arnd@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
	Wim Van Sebroeck <wim@...ux-watchdog.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Jean Delvare <jdelvare@...e.de>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org
Subject: Re: [PATCH] i2c: i801: add I2C_MUX dependency

On Sat, Apr 06, 2024 at 05:45:57PM +0200, Arnd Bergmann wrote:
> On Sat, Apr 6, 2024, at 15:08, Guenter Roeck wrote:
> > On Fri, Apr 05, 2024 at 04:27:43PM +0200, Arnd Bergmann wrote:
> >> 
> >> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> >> index 1872f1995c77..2619018dd756 100644
> >> --- a/drivers/i2c/busses/Kconfig
> >> +++ b/drivers/i2c/busses/Kconfig
> >> @@ -108,6 +108,7 @@ config I2C_HIX5HD2
> >>  config I2C_I801
> >>  	tristate "Intel 82801 (ICH/PCH)"
> >>  	depends on PCI
> >> +	depends on I2C_MUX || I2C_MUX_GPIO=n
> >>  	select P2SB if X86
> >>  	select CHECK_SIGNATURE if X86 && DMI
> >>  	select I2C_SMBUS
> >> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> >> index 0b0df3fe1efd..4dfb3773e6e2 100644
> >> --- a/drivers/watchdog/Kconfig
> >> +++ b/drivers/watchdog/Kconfig
> >> @@ -1301,8 +1301,6 @@ config ITCO_WDT
> >>  	select WATCHDOG_CORE
> >>  	depends on I2C || I2C=n
> >>  	depends on MFD_INTEL_PMC_BXT || !MFD_INTEL_PMC_BXT
> >> -	select LPC_ICH if !EXPERT
> >> -	select I2C_I801 if !EXPERT && I2C
> >
> > Sorry, I don't understand why LPC_ICH and I2C_I801 are neither a dependency
> > nor need to be selected. What if both LPC_ICH=n and I2C_I801=n, or if one is
> > selected but the other is needed to connect to the watchdog ?
> 
> The Kconfig dependencies are only required if there is a compile-time
> dependencies. In this case, both LPC_ICH and I2C_I801 create a
> platform device that is consumed by ITCO_WDT, but it could in
> theory work with any other such driver providing the device.
> 
> It would be fine to make this explicit by adding
> 'depends on LPC_ICH || I2C_I801' to enforce that the watchdog
> driver can only be selected on if at least one of these
> is present, but we have a lot of examples where we don't
> spell out this type of dependency.
> 

Yes, I know, there are lots of inconsistencies in the kernel and its
configuration. That should not be an excuse to making it worse.

Guenter