Message-ID: <1412100559.21730.30.camel@x220>
Date:	Tue, 30 Sep 2014 20:09:19 +0200
From:	Paul Bolle <pebolle@...cali.nl>
To:	"Yann E. MORIN" <yann.morin.1998@...e.fr>
Cc:	Michal Marek <mmarek@...e.cz>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/1] kconfig: warn if an unknown symbol is selected

This is an attempt to make a recurring kconfig issue more visible:
select statements for unknown, or unreachable, Kconfig symbols. See,
I've submitted quite a few patches that remove statements like
    select BOGUS

One of the annoying properties of kconfig is that select statements like
that are silently treated as a nop. That makes them surprisingly easy to
stay unnoticed. Some of them are caught by my local "800 line perl
monster", but not all. But perhaps silently skipping these statements is
actually considered a feature. I think it is not.

Anyhow, I've tweaked kconfig to warn about them. Then I ran kconfig on
all (500+) in tree defconfig files as of next-20140930. These are the
select statements it warns about when doing that.

The most interesting are 8 (CPU_IDLE), 10 (PREEMPT_COUNT) and 11
(ZONE_DMA).

1) arch/arm/Kconfig:429:warning: 'ARCH_EFM32' selects unknown symbol 'NO_DMA'

Unknown on arm. Patch submitted.

2) arch/arm/mach-meson/Kconfig:11:warning: 'MACH_MESON6' selects unknown symbol 'MESON6_TIMER'

Clearly bogus select. But Kconfig symbol MESON6_TIMER is apparently
queued.

3) arch/arm/mach-mvebu/Kconfig:40:warning: 'MACH_ARMADA_375' selects unknown symbol 'ARM_ERRATA_753970'
   arch/arm/mach-mvebu/Kconfig:55:warning: 'MACH_ARMADA_38X' selects unknown symbol 'ARM_ERRATA_753970'

Typo. Patch is being discussed for some time now.

4) arch/arm/mach-shmobile/Kconfig:39:warning: 'ARCH_SHMOBILE_MULTI' selects unknown symbol 'ARCH_HAS_OPP'

Unfinished Kconfig cleanup. Patches submitted and/or queued.

5) arch/hexagon/Kconfig:22:warning: 'HEXAGON' selects unknown symbol 'NO_IOPORT_MAP'

Unknown on hexagon. Patch submitted and already Acked.

6) arch/powerpc/platforms/44x/Kconfig:217:warning: 'AKEBONO' selects unknown symbol 'IBM_EMAC_RGMII_WOL'
   arch/powerpc/platforms/44x/Kconfig:223:warning: 'AKEBONO' selects unknown symbol 'MMC_SDHCI_OF_476GTR'

Clearly bogus selects. One symbol might be queued. Not sure why the
other select hasn't been removed.

7) arch/score/Kconfig:24:warning: 'ARCH_SCORE7' selects unknown symbol 'SYS_SUPPORTS_32BIT_KERNEL'
   arch/score/Kconfig:28:warning: 'MACH_SPCT6600' selects unknown symbol 'SYS_SUPPORTS_32BIT_KERNEL'
   arch/score/Kconfig:32:warning: 'SCORE_SIM' selects unknown symbol 'SYS_SUPPORTS_32BIT_KERNEL'

Bogus. Submitted a patch long ago. Nothing happened.

8) drivers/acpi/Kconfig:165:warning: 'ACPI_PROCESSOR' selects unknown symbol 'CPU_IDLE'

Unreachable for eg ia64. Perhaps fixed by:
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -162,7 +162,7 @@ config ACPI_DOCK
 config ACPI_PROCESSOR
        tristate "Processor"
        select THERMAL
-       select CPU_IDLE
+       select CPU_IDLE if (ARM || ARM64 || MIPS || PPC || X86 || SUPERH)
        default y
        help
          This driver installs ACPI as the idle handler for Linux and uses
 
9) drivers/irqchip/Kconfig:16:warning: 'ARM_GIC_V3' selects unknown symbol 'MULTI_IRQ_HANDLER'
   drivers/irqchip/Kconfig:8:warning: 'ARM_GIC' selects unknown symbol 'MULTI_IRQ_HANDLER'

MULTI_IRQ_HANDLER is arm specific. So arm64 builds trigger this.
Suggested fix:
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -5,7 +5,7 @@ config IRQCHIP
 config ARM_GIC
        bool
        select IRQ_DOMAIN
-       select MULTI_IRQ_HANDLER
+       select MULTI_IRQ_HANDLER if ARM
 
 config GIC_NON_BANKED
        bool
@@ -13,7 +13,6 @@ config GIC_NON_BANKED
 config ARM_GIC_V3
        bool
        select IRQ_DOMAIN
-       select MULTI_IRQ_HANDLER
 
 config ARM_NVIC
        bool

10) lib/Kconfig.debug:1008:warning: 'DEBUG_ATOMIC_SLEEP' selects unknown symbol 'PREEMPT_COUNT'

Not all architectures have PREEMPT_COUNT. Maybe fixed by:
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1005,7 +1005,7 @@ config DEBUG_LOCKDEP
 
 config DEBUG_ATOMIC_SLEEP
        bool "Sleep inside atomic section checking"
-       select PREEMPT_COUNT
+       select PREEMPT_COUNT if !(ALPHA || FRV || HEXAGON || UML)
        depends on DEBUG_KERNEL
        help
          If you say Y here, various routines which may sleep will become very

Not sure, however.

11) sound/pci/Kconfig:158:warning: 'SND_AZT3328' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:28:warning: 'SND_ALS300' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:466:warning: 'SND_EMU10K1' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:482:warning: 'SND_EMU10K1X' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:516:warning: 'SND_ES1938' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:528:warning: 'SND_ES1968' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:53:warning: 'SND_ALI5451' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:615:warning: 'SND_ICE1712' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:703:warning: 'SND_MAESTRO3' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:812:warning: 'SND_SONICVIBES' selects unknown symbol 'ZONE_DMA'
    sound/pci/Kconfig:824:warning: 'SND_TRIDENT' selects unknown symbol 'ZONE_DMA'

Seen on parisc and sh. Tricky. See commit 80ab8eae70e5 ("ALSA: Enable
CONFIG_ZONE_DMA for smaller PCI DMA masks"). Nice quote from Andrew
Morton about adding these selects (instead of fixing the underlying
problem):
    But then we'll just forget about it :(

(https://bugzilla.kernel.org/show_bug.cgi?id=68221#c19 ).

Comments welcome!

Paul Bolle (1):
  kconfig: warn if an unknown symbol is selected

 scripts/kconfig/conf.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

-- 
1.9.3

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