From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valdis.Kletnieks@vt.edu Subject: Re: kbuild: fixing the select problem Date: Thu, 06 May 2010 12:47:07 -0400 Message-ID: <28312.1273164427@localhost> References: <1273096160.23208.35.camel@mulgrave.site> <1273151844.23208.48.camel@mulgrave.site> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1273164427_4019P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Your message of "Thu, 06 May 2010 09:17:24 EDT." <1273151844.23208.48.camel@mulgrave.site> Sender: linux-kbuild-owner@vger.kernel.org To: James Bottomley Cc: Geert Uytterhoeven , linux-arch@vger.kernel.org, linux-kernel , Sam Ravnborg , linux-kbuild@vger.kernel.org, Randy Dunlap List-Id: linux-arch.vger.kernel.org --==_Exmh_1273164427_4019P Content-Type: text/plain; charset=us-ascii On Thu, 06 May 2010 09:17:24 EDT, James Bottomley said: > On Thu, 2010-05-06 at 08:47 +0200, Geert Uytterhoeven wrote: > > On Wed, May 5, 2010 at 23:49, James Bottomley > > wrote: > > > [Sam: I know you don't maintain kbuild anymore, but since you have the > > > most experience, if you could find time to comment, I'd be grateful] > > > > > > The select problem is that the kbuild select directive will turn a > > > symbol on without reference to its dependencies. This, in turn, means > > > that either selected symbols must select their dependencies, or that > > > people using select have to be aware of the selected symbol's dependency > > > and build those dependencies into their symbol (leading to duplication > > > and the possibility of getting the dependencies out of sync). We use > > > select for the scsi transport classes, so we run into this problem in > > > SCSI quite a lot. > > > > > > I think the correct fix is to make a symbol that selects another symbol > > > automatically inherit all of the selected symbol's dependencies. > > > > What if there's a good reason the selected symbol has this dependency? > > E.g. it depends on a critical feature not available? Like CONFIG_HAS_IOMEM? > > I don't quite understand the question. If a selected symbol has a > critical dependency which is config'd to N then the build usually > breaks ... that's what I'm calling the select problem. I thought > CONFIG_HAS_IOMEM was usually selected by the architecture, though. In > the new proposal, we wouldn't be able to generate the invalid > configuration in the first place. I think Geert is asking "If the arch says CONFIG_HAS_IOMEM=n, but some driver does a 'select CONFIG_FOO' which then (under your proposal) forces the value CONFIG_BAR=y, which eventually ends up with CONFIG_HAS_IOMEM=y, what should the behavior be?" (I suspect the right answer here is "one of the symbols is buggy and its 'select' should be a 'depends' instead", but somebody else better double-check that conclusion - I'm hardly a Kconfig expert). --==_Exmh_1273164427_4019P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFL4vKLcC3lWbTT17ARAgE5AJ43psqTT7rYy0JcknGfXKbMiJD5ugCeORV6 7EXqMun2Vq5ohJHT4EhZFEI= =X0zm -----END PGP SIGNATURE----- --==_Exmh_1273164427_4019P-- From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lennier.cc.vt.edu ([198.82.162.213]:55257 "EHLO lennier.cc.vt.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759158Ab0EFQr1 (ORCPT ); Thu, 6 May 2010 12:47:27 -0400 Subject: Re: kbuild: fixing the select problem In-Reply-To: Your message of "Thu, 06 May 2010 09:17:24 EDT." <1273151844.23208.48.camel@mulgrave.site> From: Valdis.Kletnieks@vt.edu References: <1273096160.23208.35.camel@mulgrave.site> <1273151844.23208.48.camel@mulgrave.site> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1273164427_4019P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Thu, 06 May 2010 12:47:07 -0400 Message-ID: <28312.1273164427@localhost> Sender: linux-arch-owner@vger.kernel.org List-ID: To: James Bottomley Cc: Geert Uytterhoeven , linux-arch@vger.kernel.org, linux-kernel , Sam Ravnborg , linux-kbuild@vger.kernel.org, Randy Dunlap Message-ID: <20100506164707.t7rfXNBWqO-kNmblaXxOh3lrJtnUxMJWIrrOa7BUGwI@z> --==_Exmh_1273164427_4019P Content-Type: text/plain; charset=us-ascii On Thu, 06 May 2010 09:17:24 EDT, James Bottomley said: > On Thu, 2010-05-06 at 08:47 +0200, Geert Uytterhoeven wrote: > > On Wed, May 5, 2010 at 23:49, James Bottomley > > wrote: > > > [Sam: I know you don't maintain kbuild anymore, but since you have the > > > most experience, if you could find time to comment, I'd be grateful] > > > > > > The select problem is that the kbuild select directive will turn a > > > symbol on without reference to its dependencies. This, in turn, means > > > that either selected symbols must select their dependencies, or that > > > people using select have to be aware of the selected symbol's dependency > > > and build those dependencies into their symbol (leading to duplication > > > and the possibility of getting the dependencies out of sync). We use > > > select for the scsi transport classes, so we run into this problem in > > > SCSI quite a lot. > > > > > > I think the correct fix is to make a symbol that selects another symbol > > > automatically inherit all of the selected symbol's dependencies. > > > > What if there's a good reason the selected symbol has this dependency? > > E.g. it depends on a critical feature not available? Like CONFIG_HAS_IOMEM? > > I don't quite understand the question. If a selected symbol has a > critical dependency which is config'd to N then the build usually > breaks ... that's what I'm calling the select problem. I thought > CONFIG_HAS_IOMEM was usually selected by the architecture, though. In > the new proposal, we wouldn't be able to generate the invalid > configuration in the first place. I think Geert is asking "If the arch says CONFIG_HAS_IOMEM=n, but some driver does a 'select CONFIG_FOO' which then (under your proposal) forces the value CONFIG_BAR=y, which eventually ends up with CONFIG_HAS_IOMEM=y, what should the behavior be?" (I suspect the right answer here is "one of the symbols is buggy and its 'select' should be a 'depends' instead", but somebody else better double-check that conclusion - I'm hardly a Kconfig expert). --==_Exmh_1273164427_4019P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFL4vKLcC3lWbTT17ARAgE5AJ43psqTT7rYy0JcknGfXKbMiJD5ugCeORV6 7EXqMun2Vq5ohJHT4EhZFEI= =X0zm -----END PGP SIGNATURE----- --==_Exmh_1273164427_4019P--