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

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Message-ID: <35e0b5cf-f7d8-4329-8dba-1098ed9451dd@gmail.com>
Date: Fri, 5 Apr 2024 21:18:37 +0200
From: Heiner Kallweit <hkallweit1@...il.com>
To: Arnd Bergmann <arnd@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
 Wim Van Sebroeck <wim@...ux-watchdog.org>, Guenter Roeck
 <linux@...ck-us.net>, Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: Arnd Bergmann <arnd@...db.de>,
 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 05.04.2024 16:27, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> When I2C_MUX is a loadable module but I2C_I801 is built-in, the newly
> added notifier function causes a link error:
> 
> x86_64-linux-ld: drivers/i2c/busses/i2c-i801.o: in function `i801_notifier_call':
> i2c-i801.c:(.text+0x1f5): undefined reference to `i2c_root_adapter'
> 
> This code is only built if I2C_MUX_GPIO is also enabled, so add a
> conditional dependency that allows building the driver as before if the
> GPIO part is disabled, but otherwise require the linker dependency at
> Kconfig level.
> 
> With the added dependency, the driver cannot be selected by a builtin
> ITCO_WDT driver when I2C_MUX_GPIO is a loadable module, so remove
> the 'select' statement in that driver as well. This was apparently
> never needed at compile-time, and the watchdog driver just needs either
> the LPC or the I2C drivers, but never both.
> 
> Configurations that rely on the implied 'select' from the watchdog
> driver now need to enable all three.
> 

Question is whether we really want that I2C_MUX restricts the choice for
I2C_I801. Alternatively we can skip building the mux part in the problem case.
The mux part can be used on very few old Asus systems with > 8 memory slots only.
Proposal I sent:
https://lore.kernel.org/all/4dhfyaefnw2rtx5q7aaum6pfwha5o3vs65iqcrj2ghps34ubtw@b3bw3gggudjs/T/

Note also the CI bot tags, as the problem was reported by a CI bot before.

> Fixes: 71b494e043d2 ("i2c: i801: Call i2c_register_spd for muxed child segments")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/i2c/busses/Kconfig | 1 +
>  drivers/watchdog/Kconfig   | 2 --
>  2 files changed, 1 insertion(+), 2 deletions(-)
> 
> 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
>  	help
>  	  Hardware driver for the intel TCO timer based watchdog devices.
>  	  These drivers are included in the Intel 82801 I/O Controller