linux-kernel - Re: [PATCH v5 1/2] dax: introduce CONFIG_DAX

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Message-ID: <CAPcyv4h9BaNutbs+D3KAox9sv9A72k1NhNs-ftHhQXU21+DYAQ@mail.gmail.com>
Date:   Fri, 29 Sep 2017 07:47:05 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Mike Snitzer <snitzer@...hat.com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        dm-devel@...hat.com, Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Bart Van Assche <Bart.VanAssche@....com>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>
Subject: Re: [PATCH v5 1/2] dax: introduce CONFIG_DAX_DRIVER

On Thu, Sep 28, 2017 at 11:11 PM, Michael Ellerman <mpe@...erman.id.au> wrote:
> Dan Williams <dan.j.williams@...el.com> writes:
>
>> In support of allowing device-mapper to compile out idle/dead code when
>> there are no dax providers in the system, introduce the DAX_DRIVER
>> symbol. This is selected by all leaf drivers that device-mapper might be
>> layered on top. This allows device-mapper to conditionally 'select DAX'
>> only when a provider is present.
>>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: Michael Ellerman <mpe@...erman.id.au>
>> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
>> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
>> Cc: Gerald Schaefer <gerald.schaefer@...ibm.com>
>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Cc: Mike Snitzer <snitzer@...hat.com>
>> Cc: Bart Van Assche <Bart.VanAssche@....com>
>> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>> ---
>>  arch/powerpc/platforms/Kconfig |    1 +
>>  drivers/block/Kconfig          |    1 +
>>  drivers/dax/Kconfig            |    4 +++-
>>  drivers/nvdimm/Kconfig         |    1 +
>>  drivers/s390/block/Kconfig     |    1 +
>>  5 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
>> index 4fd64d3f5c44..4561340c1f92 100644
>> --- a/arch/powerpc/platforms/Kconfig
>> +++ b/arch/powerpc/platforms/Kconfig
>> @@ -296,6 +296,7 @@ config AXON_RAM
>>       tristate "Axon DDR2 memory device driver"
>>       depends on PPC_IBM_CELL_BLADE && BLOCK
>>       select DAX
>> +     select DAX_DRIVER
>
>
> I would have thought you'd want to replace the select of DAX with
> a select of DAX_DRIVER?

Me too ;-)

> With the driver selecting both there's no need for the core to select
> DAX, because all the DAX drivers have done it already.

Thanks, yes, I'll fix that up.