linux-kernel - Re: [PATCH] cxl: fix FWCTL dependency

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Message-ID: <67cf2f01dac80_11511294e@dwillia2-xfh.jf.intel.com.notmuch>
Date: Mon, 10 Mar 2025 11:27:13 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Arnd Bergmann <arnd@...nel.org>, Davidlohr Bueso <dave@...olabs.net>,
	Jonathan Cameron <jonathan.cameron@...wei.com>, Dave Jiang
	<dave.jiang@...el.com>, Alison Schofield <alison.schofield@...el.com>,
	"Vishal Verma" <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
	"Dan Williams" <dan.j.williams@...el.com>, Li Ming <ming.li@...omail.com>,
	"Jason Gunthorpe" <jgg@...pe.ca>
CC: Arnd Bergmann <arnd@...db.de>, Robert Richter <rrichter@....com>, "Mike
 Rapoport (Microsoft)" <rppt@...nel.org>, Masahiro Yamada
	<masahiroy@...nel.org>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cxl: fix FWCTL dependency

Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The 'FWCTL' subsystem is selected by CXL_FEATURES, which is a 'bool' symbol
> with a dependency on CXL_PCI, but referenced by the cxl_core.ko.
> When cxl_core is built-in, but the cxl_pci.ko driver is a loadable mdoule,
> this results in a link failure:
> 
> ld.lld-21: error: undefined symbol: _fwctl_alloc_device
> >>> referenced by features.c:695 (/home/arnd/arm-soc/drivers/cxl/core/features.c:695)
> ld.lld-21: error: undefined symbol: fwctl_register
> >>> referenced by features.c:699 (/home/arnd/arm-soc/drivers/cxl/core/features.c:699)
> ld.lld-21: error: undefined symbol: fwctl_unregister
> >>> referenced by features.c:676 (/home/arnd/arm-soc/drivers/cxl/core/features.c:676)
> 
> Move the 'select' into the symbol that controls the core module instead.
> 
> Fixes: a53a6004e7a5 ("cxl: Add FWCTL support to CXL")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/cxl/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
> index ed49e7e7e5bc..cf1ba673b8c2 100644
> --- a/drivers/cxl/Kconfig
> +++ b/drivers/cxl/Kconfig
> @@ -7,6 +7,7 @@ menuconfig CXL_BUS
>  	select PCI_DOE
>  	select FIRMWARE_TABLE
>  	select NUMA_KEEP_MEMINFO if NUMA_MEMBLKS
> +	select FWCTL if CXL_FEATURES

Looks good,

Reviewed-by: Dan Williams <dan.j.williams@...el.com>

...I tried to find a way to keep it local to the CXL_FEATURES symbol,
but it really is an optional core feature that needs to have the select
from the core module like you have it.

>  	help
>  	  CXL is a bus that is electrically compatible with PCI Express, but
>  	  layers three protocols on that signalling (CXL.io, CXL.cache, and
> @@ -105,7 +106,6 @@ config CXL_MEM
>  config CXL_FEATURES
>  	bool "CXL: Features"
>  	depends on CXL_PCI

Drive-by observation for an additional cleanup that this CXL_PCI
dependency is bogus. If it were real then there would be a circular
dependency between cxl_pci.ko and cxl_core.ko. As is this is just noise
in the Kconfig file since the dependency solver would already be
screaming if this was a true dependency.