linux-kernel - Re: [PATCH v3 1/2] binder: Add default binder devices through binderfs when configured

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Message-ID: <CA+wgaPNjfvcVvcDB9ZBWupLegHchZ3AxYibBV8BPFE9SrPymtg@mail.gmail.com>
Date:   Fri, 9 Aug 2019 13:08:01 -0700
From:   Hridya Valsaraju <hridya@...gle.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 1/2] binder: Add default binder devices through
 binderfs when configured

On Fri, Aug 9, 2019 at 11:22 AM Christian Brauner
<christian.brauner@...ntu.com> wrote:
>
> On Fri, Aug 09, 2019 at 04:50:16PM +0200, Greg Kroah-Hartman wrote:
> > On Thu, Aug 08, 2019 at 03:27:25PM -0700, Hridya Valsaraju wrote:
> > > Currently, since each binderfs instance needs its own
> > > private binder devices, every time a binderfs instance is
> > > mounted, all the default binder devices need to be created
> > > via the BINDER_CTL_ADD IOCTL.
> >
> > Wasn't that a design goal of binderfs?
>
> Sure, but if you solely rely binderfs to be used to provide binder
> devices having them pre-created on each mount makes quite some sense,
> imho.
>
> >
> > > This patch aims to
> > > add a solution to automatically create the default binder
> > > devices for each binderfs instance that gets mounted.
> > > To achieve this goal, when CONFIG_ANDROID_BINDERFS is set,
> > > the default binder devices specified by CONFIG_ANDROID_BINDER_DEVICES
> > > are created in each binderfs instance instead of global devices
> > > being created by the binder driver.
> >
> > This is going to change how things work today, what is going to break
> > because of this change?
> >
> > I don't object to this, except for the worry of changing the default
> > behavior.
>
> This is something that Hridya and Todd can speak better to given that
> they suggested this change. :)
> From my perspective, binderfs binder devices and the regular binder
> driver are mostly used mutually exclusive in practice atm so that this
> change has little chance of breaking anyone.

As Christian says, we do not anticipate the change to break any
existing use cases since binderfs binder devices and regular binder
devices are generally not used simultaneously. Hopefully, there are
not a lot of unusual use cases since binderfs itself is relatively new
as well :)


>
> Now I really need to go back to vacation time - which I suck at
> apparently. :)
>
> Christian