From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3tCHps1R3qzDvMQ for ; Tue, 8 Nov 2016 03:25:09 +1100 (AEDT) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3tCHpr5FjWz9vFF for ; Tue, 8 Nov 2016 03:25:08 +1100 (AEDT) Date: Mon, 7 Nov 2016 09:25:05 -0700 From: Alex Williamson To: Michael Ellerman Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, aik@ozlabs.ru, gwshan@linux.vnet.ibm.com Subject: Re: [PATCH] vfio: Fix build break when SPAPR_TCE_IOMMU=n Message-ID: <20161107092505.429f07d6@t450s.home> In-Reply-To: <87zilblmcd.fsf@concordia.ellerman.id.au> References: <1478238521-32203-1-git-send-email-mpe@ellerman.id.au> <81900126-f1aa-b480-c2fa-f0fa04d625c1@redhat.com> <87zilblmcd.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 07 Nov 2016 19:34:42 +1100 Michael Ellerman wrote: > Paolo Bonzini writes: > > On 04/11/2016 06:48, Michael Ellerman wrote: > >> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig > >> index da6e2ce77495..6b51a4ebed8a 100644 > >> --- a/drivers/vfio/Kconfig > >> +++ b/drivers/vfio/Kconfig > >> @@ -6,12 +6,12 @@ config VFIO_IOMMU_TYPE1 > >> config VFIO_IOMMU_SPAPR_TCE > >> tristate > >> depends on VFIO && SPAPR_TCE_IOMMU > >> - default n > >> + default VFIO > > > > No need to depend on VFIO since you already have it in "default". depends and defaults are different beasts though, if VFIO is not enabled and we're not on a powerpc system with SPAPR, VFIO_IOMMU_SPAPR_TCE should not be selectable, not just default to 'n'. > > True, I can take that out. > > > (I assume you cannot use "default y" because "depends on" doesn't downgrade > > "y" to "m" when VFIO is a module. > > Correct. > > > A shorthand is > > > > def_tristate VFIO && SPAPR_TCE_IOMMU > > Yep. My experience though is that a lot of folks don't really know what > that means. So I prefer to spell it out with an explicit type, depends > and default. > > But I'll respin it that way if Alex prefers the shorter style. Perhaps I'm one of those people. Non-powerpc archs should not have an option to select this, which is why the depends is there, AIUI. So long as we don't start exposing options that aren't relevant to a platform, I'm flexible on what shorthands we use, but you may need to teach me about them first. Thanks, Alex