Re: [PATCH 4/8] pci: consolidate PCI config entry in drivers/pci

[Masahiro Yamada]

On Sun, Oct 14, 2018 at 12:11 AM Christoph Hellwig <hch@xxxxxx> wrote:
>
> There is no good reason to duplicate the PCI menu in every architecture.
> Instead provide a selectable HAS_PCI symbol that indicates availability
> of PCI support and the handle the rest in drivers/pci.


I think HAVE_ is a preferred prefix in this case according to this doc:
https://github.com/masahir0y/linux/blob/v4.19-rc4/Documentation/kbuild/kconfig-language.txt#L448


It is true we have some options with HAS_ prefix,
but the majority is HAVE_.

masahiro@pug:~/ref/linux$ find . -name 'Kconfig*' | xargs grep 'config
HAS_' | wc
      9      18     355
masahiro@pug:~/ref/linux$ find . -name 'Kconfig*' | xargs grep 'config
HAVE_' | wc
    177     354    8182





> Note that for powerpc we now select HAS_PCI globally instead of the
> convoluted mess of conditional or or non-conditional support per board,
> similar to what we do e.g. on x86.  For alpha PCI is selected for the
> non-jensen configs as it was the default before, and a lot of code does
> not compile without PCI enabled.  On other architectures with limited
> PCI support that wasn't as complicated I've left the selection as-is.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---



> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 6fa6f92edb7f..0713375e1127 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -168,10 +168,16 @@ config PPC
>         select GENERIC_CPU_VULNERABILITIES      if PPC_BARRIER_NOSPEC
>         select GENERIC_IRQ_SHOW
>         select GENERIC_IRQ_SHOW_LEVEL
> +       select GENERIC_PCI_IOMAP                if PCI
>         select GENERIC_SMP_IDLE_THREAD
>         select GENERIC_STRNCPY_FROM_USER
>         select GENERIC_STRNLEN_USER
>         select GENERIC_TIME_VSYSCALL
> +       # Platforms that what PCI turned unconditionally just do select PCI
> +       # in their config node, otherwise allow the user to enable it.
> +       # This means we can enable PCI even on platforms that don't support
> +       # it, which is harmless except for wasted memory.
> +       select HAS_PCI


If you do this for entire powerpc,
the other 'select HAS_PCI' addtions to
arch/powerpc/platforms/*/Kconfig look redundant.





> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index a344980287a5..6eb31a0698ac 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -38,6 +38,7 @@ config RISCV
>         select RISCV_ISA_A if SMP
>         select SPARSE_IRQ
>         select SYSCTL_EXCEPTION_TRACE
> +       select HAS_PCI
>         select HAVE_ARCH_TRACEHOOK
>         select MODULES_USE_ELF_RELA if MODULES
>         select THREAD_INFO_IN_TASK
> @@ -216,28 +217,12 @@ source "kernel/Kconfig.hz"
>
>  endmenu
>
> -menu "Bus support"
> -
> -config PCI
> -       bool "PCI support"
> -       select PCI_MSI


I think this 'select PCI_MSI' for riscv was lost.




> -       help
> -         This feature enables support for PCI bus system. If you say Y
> -         here, the kernel will include drivers and infrastructure code
> -         to support PCI bus devices.
> -
> -         If you don't know what to do here, say Y.
> -
>  config PCI_DOMAINS
>         def_bool PCI
>
>  config PCI_DOMAINS_GENERIC
>         def_bool PCI
>
> -source "drivers/pci/Kconfig"
> -
> -endmenu
> -
>  menu "Power management options"
>
>  source kernel/power/Kconfig



> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 1a0be022f91d..7cbc656f47e7 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -113,6 +113,7 @@ config X86
>         select GENERIC_STRNLEN_USER
>         select GENERIC_TIME_VSYSCALL
>         select HARDLOCKUP_CHECK_TIMESTAMP       if X86_64
> +       select HAS_PCI
>         select HAVE_ACPI_APEI                   if ACPI
>         select HAVE_ACPI_APEI_NMI               if ACPI
>         select HAVE_ALIGNED_STRUCT_PAGE         if SLUB
> @@ -2567,15 +2568,6 @@ endmenu
>
>  menu "Bus options (PCI etc.)"
>
> -config PCI
> -       bool "PCI support"
> -       default y


The default is y for x86 (and xtensa as well).

With this patch, the default will be flipped.

I think most of people want to use PCI for x86,
and this change will make people upset.

Will you update arch/{x86,xtensa}/configs/*_defconfig?






> -       ---help---
> -         Find out whether you have a PCI motherboard. PCI is the name of a
> -         bus system, i.e. the way the CPU talks to the other stuff inside
> -         your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
> -         VESA. If you have PCI, say Y, otherwise N.
> -
>  choice
>         prompt "PCI access mode"
>         depends on X86_32 && PCI
> @@ -2658,8 +2650,6 @@ config PCI_CNB20LE_QUIRK
>
>           You should say N unless you know you need this.
>
> -source "drivers/pci/Kconfig"
> -
>  config ISA_BUS
>         bool "ISA bus support on modern systems" if EXPERT
>         help
> diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
> index b9ad83a0ee5d..22abeb236863 100644
> --- a/arch/xtensa/Kconfig
> +++ b/arch/xtensa/Kconfig
> @@ -20,6 +20,7 @@ config XTENSA
>         select GENERIC_PCI_IOMAP
>         select GENERIC_SCHED_CLOCK
>         select GENERIC_STRNCPY_FROM_USER if KASAN
> +       select HAS_PCI
>         select HAVE_ARCH_KASAN if MMU
>         select HAVE_DEBUG_KMEMLEAK
>         select HAVE_DMA_CONTIGUOUS
> @@ -384,21 +385,6 @@ config XTENSA_CALIBRATE_CCOUNT
>  config SERIAL_CONSOLE
>         def_bool n
>
> -menu "Bus options"
> -
> -config PCI
> -       bool "PCI support"
> -       default y
> -       help
> -         Find out whether you have a PCI motherboard. PCI is the name of a
> -         bus system, i.e. the way the CPU talks to the other stuff inside
> -         your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
> -         VESA. If you have PCI, say Y, otherwise N.
> -
> -source "drivers/pci/Kconfig"
> -
> -endmenu
> -
>  menu "Platform options"
>
>  choice
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index ab4d43923c4d..059573823387 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -1,7 +1,11 @@
>  # SPDX-License-Identifier: GPL-2.0
>  menu "Device Drivers"
>
> +# Keep I/O buses first
> +
>  source "drivers/amba/Kconfig"
> +source "drivers/pci/Kconfig"
> +
>
>  source "drivers/base/Kconfig"
>
> diff --git a/drivers/parisc/Kconfig b/drivers/parisc/Kconfig
> index 5a48b5606110..5bbfea1a019c 100644
> --- a/drivers/parisc/Kconfig
> +++ b/drivers/parisc/Kconfig
> @@ -63,17 +63,6 @@ config ISA
>           If you want to plug an ISA card into your EISA bus, say Y here.
>           Most people should say N.
>
> -config PCI
> -       bool "PCI support"
> -       help
> -         All recent HP machines have PCI slots, and you should say Y here
> -         if you have a recent machine.  If you are convinced you do not have
> -         PCI slots in your machine (eg a 712), then you may say "N" here.
> -         Beware that some GSC cards have a Dino onboard and PCI inside them,
> -         so it may be safest to say "Y" anyway.
> -
> -source "drivers/pci/Kconfig"
> -
>  config GSC_DINO
>         bool "GSCtoPCI/Dino PCI support"
>         depends on PCI && GSC
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index 56ff8f6d31fc..229a518b68cd 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -3,6 +3,18 @@
>  # PCI configuration
>  #
>
> +config HAS_PCI
> +       bool
> +
> +menuconfig PCI
> +       bool "PCI support"
> +       depends on HAS_PCI
> +
> +       help
> +         This option enables support for the PCI local bus, including
> +         support for PCI-X and the fundations for PCI Express support.
> +         Say 'Y' here unless you know what you are doing.
> +
>  source "drivers/pci/pcie/Kconfig"
>
>  config PCI_MSI
> --
> 2.19.1
>


--
Best Regards
Masahiro Yamada