linux-kernel - Re: [RFC v1] tree-wide: remove "select FW

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Message-ID: <20150522222200.GP23057@wotan.suse.de>
Date:	Sat, 23 May 2015 00:22:00 +0200
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	josh@...htriplett.org
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Takashi Iwai <tiwai@...e.de>, Paul Bolle <pebolle@...cali.nl>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Borislav Petkov <bp@...en8.de>,
	Greg KH <gregkh@...uxfoundation.org>,
	"David S. Miller" <davem@...emloft.net>, clemens@...isch.de,
	JBottomley@...n.com, David Airlie <airlied@...ux.ie>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Marcel Holtmann <marcel@...tmann.org>,
	"Gustavo F. Padovan" <gustavo@...ovan.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	Mikael Starvik <starvik@...s.com>,
	Jesper Nilsson <jesper.nilsson@...s.com>,
	Imre Kaloz <kaloz@...nwrt.org>, khalasa@...p.pl,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Arnd Bergmann <arnd@...db.de>, 3chas3@...il.com,
	Jiri Slaby <jslaby@...e.cz>, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	mcgrof@...not-panic.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v1] tree-wide: remove "select FW_LOADER" uses

On Fri, May 22, 2015 at 02:43:57PM -0700, josh@...htriplett.org wrote:
> On Fri, May 22, 2015 at 09:28:14PM +0200, Luis R. Rodriguez wrote:
> > So the question still stands -- are there any kconfig options which
> > depend on EXPERT which enable folks to screw up run time (not just driver
> > tweaks?
> 
> I don't think it should be possible

OK, thanks!

> > So unless I'm missing a corner case, it would seem replacing "select FW_LOADER"
> > with "depends on FW_LOADER" is a reasonable option so far. The subtleties lie
> > then now in since EXPERT is used by most distributions, everyone is an expert,
> > and:
> > 
> >   a) Do we want to be consistent about ensuring run time sanity of EXPERT?
> >   b) Should we split EXPERT into tweak / possible run time break options?
> 
> "depends on FW_LOADER" and "select FW_LOADER" are equivalent from the
> point of view of what configs they allow; they differ in how the
> dependency is shown in UIs.
>
> However, from the sounds of things, you want to add a dependency to
> FW_LOADER.

Nope the recursive case was that a new component which depends on
FW_LOADER ended up selecting CRYPTO, and it turns out another driver
which depends on FW_LOADER also depended on CRYPTO so that in turn
creates a recursive dependency.

> So in that case, yeah, switch to depends rather than
> rewriting Kconfig, unless you're feeling really ambitious.

OK so switching to "depends on" is the winning contender so far.

> > > > Note that not changing this means we *will* eventually run into the
> > > > recursive dependency issue later, either with my FW API change patches
> > > > or some other future feature. Likewise for any other kconfig option
> > > > with similar semantics.
> 
> By "recursive dependency issue", I'm guessing that someone wants to make
> FW_LOADER depend on something else, which breaks because "select"
> doesn't know how to recurse?

Kind of, the issue actually was a new component which depends on FW_LOADER
and has crypto dependencies. Since the qat crypto driver selects FW_LOADER
but also has a set of crypto dependencies that creates a recursive dependency
loop.

> Ideally, someone should teach Kconfig to handle recursive dependencies,
> but in the meantime using "depends" makes sense.

Doesn't sound like anyone is that enthusiastic about that.

So... shall we just switch to "depends on" tree-wide then for FW_LOADER?

  Luis
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