linux-kernel - Re: [PATCH] cramfs: fix MTD dependency

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Message-ID: <CAK8P3a268Aq2bsPRmUmLbVFD7xQLUj49b+5yhYhC8ugbk-V4pA@mail.gmail.com>
Date:   Wed, 15 Nov 2017 15:44:18 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cramfs: fix MTD dependency

On Fri, Nov 10, 2017 at 6:01 PM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> On Fri, 10 Nov 2017, Arnd Bergmann wrote:
>
>> On Fri, Nov 10, 2017 at 5:35 PM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
>> > On Fri, 10 Nov 2017, Arnd Bergmann wrote:
>> >
>> >> With CONFIG_MTD=m and CONFIG_CRAMFS=y, we now get a link failure:
>> >>
>> >> fs/cramfs/inode.o: In function `cramfs_mount':
>> >> inode.c:(.text+0x220): undefined reference to `mount_mtd'
>> >> fs/cramfs/inode.o: In function `cramfs_mtd_fill_super':
>> >> inode.c:(.text+0x6d8): undefined reference to `mtd_point'
>> >> inode.c:(.text+0xae4): undefined reference to `mtd_unpoint'
>> >>
>> >> This adds a more specific Kconfig dependency to avoid the
>> >> broken configuration. Alternatively we could make CRAMFS
>> >> itself depend on "MTD || !MTD" with a similar result.
>> >>
>> >> Fixes: 99c18ce580c6 ("cramfs: direct memory access support")
>> >> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> >> ---
>> >>  fs/cramfs/Kconfig | 1 +
>> >>  1 file changed, 1 insertion(+)
>> >>
>> >> diff --git a/fs/cramfs/Kconfig b/fs/cramfs/Kconfig
>> >> index f937082f3244..58e2fe40b2a0 100644
>> >> --- a/fs/cramfs/Kconfig
>> >> +++ b/fs/cramfs/Kconfig
>> >> @@ -34,6 +34,7 @@ config CRAMFS_BLOCKDEV
>> >>  config CRAMFS_MTD
>> >>       bool "Support CramFs image directly mapped in physical memory"
>> >>       depends on CRAMFS && MTD
>> >> +     depends on CRAMFS=m || MTD=y
>> >
>> > I think the following is better:
>> >
>> > diff --git a/fs/cramfs/Kconfig b/fs/cramfs/Kconfig
>> > index f937082f32..a00740c668 100644
>> > --- a/fs/cramfs/Kconfig
>> > +++ b/fs/cramfs/Kconfig
>> > @@ -33,7 +33,7 @@ config CRAMFS_BLOCKDEV
>> >
>> >  config CRAMFS_MTD
>> >         bool "Support CramFs image directly mapped in physical memory"
>> > -       depends on CRAMFS && MTD
>> > +       depends on CRAMFS && (CRAMFS <= MTD)
>> >         default y if !CRAMFS_BLOCKDEV
>> >         help
>> >           This option allows the CramFs driver to load data directly from
>>
>> I've never seen that syntax, what does it mean?
>
> In the Kconfig language: n < m < y. Therefore (m < y) is true and
> (y < m) is false.

I see. However, since I didn't recognize that syntax, and it doesn't seem
to be used much, I would still prefer my original suggestion, which
I think is more common.

      Arnd