linux-kernel - Re: [PATCH] EDAC, {skx|i10nm}_edac: Fix randconfig build error

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Date:   Fri, 15 Mar 2019 22:03:43 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        James Morse <james.morse@....com>,
        Qiuxu Zhuo <qiuxu.zhuo@...el.com>, linux-edac@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] EDAC, {skx|i10nm}_edac: Fix randconfig build error

On Fri, Mar 15, 2019 at 7:11 PM Luck, Tony <tony.luck@...el.com> wrote:
>
> On Fri, Mar 15, 2019 at 07:02:06PM +0100, Borislav Petkov wrote:
> > On Fri, Mar 15, 2019 at 10:49:56AM -0700, Luck, Tony wrote:
> > > Yes - Qiuxu did that already ... patch reposted below.
> >
> > ... to which Arnd said that it were fragile because it might break if it
> > includes a THIS_MODULE reference. So I'd say we won't do that then. And
> > keep it strictly a library.
> >
> > Right?
>
> What is your definition of "library"?
>
> fsl_ddr_edac.c seems to have the same potential for breakage
> if someone makes a change to that, then it will hit the same
> problem.

I think they are a bit safer because CONFIG_EDAC_LAYERSCAPE and
CONFIG_EDAC_MPC85XX are mutually exclusive (one is only
on powerpc, the other is only on ARM). It would break though if
one were to make them build with CONFIG_COMPILE_TEST,
or if another driver gets added that for ARM.

I just thought about a possible Kconfig solution some more, and
had this idea:

diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
index 47eb4d13ed5f..70080926329f 100644
--- a/drivers/edac/Kconfig
+++ b/drivers/edac/Kconfig
@@ -235,6 +235,7 @@ config EDAC_SKX
        depends on ACPI_NFIT || !ACPI_NFIT # if ACPI_NFIT=m, EDAC_SKX can't be y
        select DMI
        select ACPI_ADXL
+       select EDAC_SKX_COMMON
        help
          Support for error detection and correction the Intel
          Skylake server Integrated Memory Controllers. If your
@@ -247,12 +248,20 @@ config EDAC_I10NM
        depends on ACPI_NFIT || !ACPI_NFIT # if ACPI_NFIT=m,
EDAC_I10NM can't be y
        select DMI
        select ACPI_ADXL
+       select EDAC_SKX_COMMON
        help
          Support for error detection and correction the Intel
          10nm server Integrated Memory Controllers. If your
          system has non-volatile DIMMs you should also manually
          select CONFIG_ACPI_NFIT.

+config EDAC_SKX_COMMON
+       tristate
+       help
+         This is an internal helper symbol to ensure that all variants
+         of the EDAC_SKX driver are either built-in or modular, as mixing
+         the two causes link time problems.
+
 config EDAC_PND2
        tristate "Intel Pondicherry2"
        depends on PCI && X86_64 && X86_MCE_INTEL
diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
index 89ad4a84a0f6..01134051f5bf 100644
--- a/drivers/edac/Makefile
+++ b/drivers/edac/Makefile
@@ -58,10 +58,14 @@ layerscape_edac_mod-y                       :=
fsl_ddr_edac.o layerscape_edac.o
 obj-$(CONFIG_EDAC_LAYERSCAPE)          += layerscape_edac_mod.o

 skx_edac-y                             := skx_common.o skx_base.o
-obj-$(CONFIG_EDAC_SKX)                 += skx_edac.o
+ifdef CONFIG_EDAC_SKX
+obj-$(CONFIG_EDAC_SKX_COMMON)          += skx_edac.o
+endif

 i10nm_edac-y                           := skx_common.o i10nm_base.o
+ifdef CONFIG_EDAC_I10NM
 obj-$(CONFIG_EDAC_SKX_COMMON)           += i10nm_edac.o
+endif

 obj-$(CONFIG_EDAC_MV64X60)             += mv64x60_edac.o
 obj-$(CONFIG_EDAC_CELL)                        += cell_edac.o

Basically I cheat Kconfig, so if one driver is built-in and
the other is a loadable module, we compile both as built-in.


        Arnd