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

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Message-ID: <nycvar.YSQ.7.76.1711101158530.28715@knanqh.ubzr>
Date:   Fri, 10 Nov 2017 12:01:28 -0500 (EST)
From:   Nicolas Pitre <nicolas.pitre@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cramfs: fix MTD dependency

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.


Nicolas