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Subject: Re: linux-next: Tree for Apr 19 (bcache)
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        linux-bcache@vger.kernel.org,
        Kent Overstreet <kent.overstreet@gmail.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Linux Next Mailing List <linux-next@vger.kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>
References: <20210419202309.0575ad77@canb.auug.org.au>
 <66d41349-60ba-f27f-5c56-3520a40dd83f@infradead.org>
 <f4ca485d-614b-6924-63bc-0948d087bdc3@suse.de>
 <76e63e74-2237-f672-eb10-edde017bc76e@kernel.dk>
From:   Coly Li <colyli@suse.de>
Message-ID: <061cd630-2740-2da9-cfbe-fd18adb22fdc@suse.de>
Date:   Tue, 20 Apr 2021 12:24:11 +0800
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On 4/20/21 1:50 AM, Jens Axboe wrote:
> On 4/19/21 10:26 AM, Coly Li wrote:
>> On 4/19/21 11:40 PM, Randy Dunlap wrote:
>>> On 4/19/21 3:23 AM, Stephen Rothwell wrote:
>>>> Hi all,
>>>>
>>>> Changes since 20210416:
>>>>
>>>
>>> on x86_64:
>>>
>>> when
>>> # CONFIG_BLK_DEV is not set
>>>
>>>
>>> WARNING: unmet direct dependencies detected for LIBNVDIMM
>>>   Depends on [n]: PHYS_ADDR_T_64BIT [=y] && HAS_IOMEM [=y] && BLK_DEV [=n]
>>>   Selected by [y]:
>>>   - BCACHE_NVM_PAGES [=y] && MD [=y] && BCACHE [=y] && PHYS_ADDR_T_64BIT [=y]
>>>
>>>
>>> Full randconfig file is attached.
>>>
>>
>> I need hint from kbuild expert.
>>
>> My original idea to use "select LIBNVDIMM" is to avoid the
>> BCACHE_NVM_PAGES option to disappear if LIBNVDIMM is not enabled.
>> Otherwise if nvdimm driver is not configure, users won't know there is a
>> BCACHE_NVM_PAGES option unless they read bcache Kconfig file.
> 
> But why? That's exactly how it should work. Just use depends to set the
> dependency.
> 
>> But I see nvdimm's Kconfig, it uses "depends on BLK_DEV", I understand
>> it is acceptable that LIBNVDIMM option to disappear from "make
>> menuconfig" if BLK_DEV is not enabled.
>>
>> For such condition, which one is the proper way to set the dependence ?
>> - Change "select LIBNVDIMM" and "select DAX" to "depends on LIBNVDIMM"
>> and "depends on DAX" in bcache Kconfig
>> - Or change "depends on BLK_DEV" to "select BLK_DEV" in nvdimm Kconfig.
> 
> The former.
> 

Copied. Thanks for the hint. I will post a fix soon.

Coly Li