linux-kernel - Re: [PATCH] configfs: change depends -> select SYSFS

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Message-ID: <1295223733.2998.8.camel@mulgrave.site>
Date:	Sun, 16 Jan 2011 18:22:12 -0600
From:	James Bottomley <James.Bottomley@...e.de>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
Cc:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Joel Becker <jlbec@...lplan.org>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: Re: [PATCH] configfs: change depends -> select SYSFS

On Mon, 2011-01-17 at 00:06 +0100, Stefan Richter wrote:
> On Jan 16 Nicholas A. Bellinger wrote:
> > On Sun, 2011-01-16 at 14:11 +0100, Stefan Richter wrote:
> > > On Jan 15 Nicholas A. Bellinger wrote:
> > > > This patch changes configfs to select SYSFS to fix the following:
> > > > 
> > > > warning: (TARGET_CORE && GFS2_FS) selects CONFIGFS_FS which has unmet direct dependencies (SYSFS)
> > > 
> > > Why don't you fix target-core's Kconfig instead?
> > 
> > The thought here was that since modern configfs is mounted
> > at /sys/kernel/config/, selecting SYSFS by default when building
> > CONFIGFS_FS made the most sense for existing configfs consumers.
> 
> I for one think that layered "select" directives will open too many cans
> of worms.

select, since we have it, should be clean ... as in if you select
something, you don't have to expose yourself to a huge pile of missing
depends that only show up in obscure configurations.

> Best don't use select at all.

The object of select is not to trip up the user.  If we used a purely
depend based configuration, the user would have to know to select, say,
the right SCSI transport classes before they get presented with drivers.
It's completely correct, since transport classes are internal
implementations, to have the user select drivers and Kconfig work out
via the select directive what transport classes are needed.

> If you use it, select only options that don't depend on anything else.
> 
> If you feel that people really want you to provide a select for them which
> selects something that in turn depends on other things, then I suggest you
> rather let your own option depend on these lower dependencies:
> 
> config HIGHLEVEL_FEATURE
> 	tristate "some driver"
> 	depends on SYSFS  # because CONFIGFS depends on it
> 	select CONFIGFS

This is what I don't understand.

Actually I think the whole premise of the patch (to get back to the
original topic) is wrong.

TARGET_CORE depends on SCSI; SCSI has to have sysfs to survive ... we
just don't work without it yet we neither select nor depend on it.
SYSFS is only deselectable for embedded anyway, so I think the
configuration which generated this whole argument was likely a bogus one
and consequently, none of the patches are needed (or if they are,
they're the tip of the iceberg).

James

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