Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753359AbdHWFg5 (ORCPT ); Wed, 23 Aug 2017 01:36:57 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:35088 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436AbdHWFg4 (ORCPT ); Wed, 23 Aug 2017 01:36:56 -0400 Date: Tue, 22 Aug 2017 22:37:00 -0700 From: Greg KH To: John Stultz Cc: Jisheng Zhang , devel@driverdev.osuosl.org, Riley Andrews , lkml , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] binder: let ANDROID_BINDER_IPC_32BIT be selectable on 32bit ARM Message-ID: <20170823053700.GC23426@kroah.com> References: <20170808110305.2748-1-jszhang@marvell.com> <20170823015108.GA18228@kroah.com> <20170823103420.6ffb5ce7@xhacker> <20170823110151.4c704574@xhacker> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3740 Lines: 81 On Tue, Aug 22, 2017 at 08:14:10PM -0700, John Stultz wrote: > On Tue, Aug 22, 2017 at 8:01 PM, Jisheng Zhang wrote: > > On Tue, 22 Aug 2017 19:57:04 -0700 John Stultz wrote: > > > >> On Tue, Aug 22, 2017 at 7:56 PM, John Stultz wrote: > >> > On Tue, Aug 22, 2017 at 7:34 PM, Jisheng Zhang wrote: > >> >> On Tue, 22 Aug 2017 18:51:08 -0700 Greg KH wrote: > >> >> > >> >>> On Tue, Aug 08, 2017 at 07:03:05PM +0800, Jisheng Zhang wrote: > >> >>> > As noted in commit d0bdff0db809 ("staging: Fix build issues with new > >> >>> > binder API"), we can add back the choice for 32bit ARM "once a 64bit > >> >>> > __get_user_asm_* implementation is merged." Commit e38361d032f1 ("ARM: > >> >>> > 8091/2: add get_user() support for 8 byte types") has added the > >> >>> > support, so it's time to let ANDROID_BINDER_IPC_32BIT be selectable on > >> >>> > 32bit ARM > >> >>> > >> >>> Ok, but: > >> >>> > >> >>> > > >> >>> > Signed-off-by: Jisheng Zhang > >> >>> > --- > >> >>> > drivers/android/Kconfig | 2 +- > >> >>> > 1 file changed, 1 insertion(+), 1 deletion(-) > >> >>> > > >> >>> > diff --git a/drivers/android/Kconfig b/drivers/android/Kconfig > >> >>> > index 832e885349b1..aca5dc30b97b 100644 > >> >>> > --- a/drivers/android/Kconfig > >> >>> > +++ b/drivers/android/Kconfig > >> >>> > @@ -32,7 +32,7 @@ config ANDROID_BINDER_DEVICES > >> >>> > therefore logically separated from the other devices. > >> >>> > > >> >>> > config ANDROID_BINDER_IPC_32BIT > >> >>> > - bool > >> >>> > + bool "Use old (Android 4.4 and earlier) 32-bit binder API" > >> >>> > depends on !64BIT && ANDROID_BINDER_IPC > >> >>> > >> >>> You don't actually change the depends line :( > >> >>> > >> >>> Please fix up, and test it, and then resend. > >> >> > >> >> IHOM, the dependency is correct: 64bit platforms don't support > >> >> ANDROID_BINDER_IPC_32BIT. What do you think? > >> > > >> > I think this indicates the commit message is unclear. > >> > > >> > Part of it is that the config is inverted from the description. The > >> > patch doesn't enable the 32bit legacy binder ABI on 32bit systems, it > >> > just allows the option to be unselected, so that the 64bit ABI will be > >> > used on 32bit systems. > >> > > >> > Conceptually I don't have an objection to the change (though maybe try > >> > to rework the commit message), but I don't have anything to actually > >> > test it on right now, so I'm hesitant to ack it. > >> > >> It might also be good to add some detail as to the motivation for this > >> change? What benefit does it bring to 32bit platforms to use the newer > >> 64bit ABI? > >> > > > > To be honest, the motivation is just to add one more choice for 32bit > > platform and let the code be tested under 32bit platform. Maybe we > > could then remove ANDROID_BINDER_IPC_32BIT and the related code after > > some time? > > I'm mixed. It would be nice to deprecate the old 32bit ABI, but binder > is a real Linux kernel interface now, so we don't break compatibility > (at least if it affects anyone - which may be questionable here - not > sure there's many upstream 32bit platforms concerned with running > legacy Android builds). But just adding the extra option just means > there's yet another configuration to test and to keep working. So you > may want to articulate the benefits better to make this worth the > effort of doing a full transition. Future versions of Android "might" be changing if they support, or not, all of the different combinations of 32/64 bit apis. So maybe we should wait until a real solid direction with regards to this is published before worrying about dropping anything... thanks, greg k-h