linux-kernel - Re: [PATCH] binder: let ANDROID_BINDER_IPC

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Message-ID: <20170824094412.1d73da94@xhacker>
Date:   Thu, 24 Aug 2017 09:44:12 +0800
From:   Jisheng Zhang <jszhang@...vell.com>
To:     Rob Herring <robh@...nel.org>
CC:     John Stultz <john.stultz@...aro.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Riley Andrews <riandrews@...roid.com>,
        <devel@...verdev.osuosl.org>, lkml <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] binder: let ANDROID_BINDER_IPC_32BIT be selectable on
 32bit ARM

On Wed, 23 Aug 2017 13:48:47 -0500 Rob Herring wrote:

> On Tue, Aug 22, 2017 at 9:57 PM, John Stultz <john.stultz@...aro.org> wrote:
> > On Tue, Aug 22, 2017 at 7:56 PM, John Stultz <john.stultz@...aro.org> wrote:  
> >> On Tue, Aug 22, 2017 at 7:34 PM, Jisheng Zhang <jszhang@...vell.com> 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 <jszhang@...vell.com>
> >>>> > ---
> >>>> >  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?  
> 
> It allows running the same 32-bit userspace build whether the kernel
> is 64-bit or 32-bit.
> 

Oh, yes, this is a good "motivation" which can be added into the commit msg.

thanks for the inspiration.