linux-kernel - Re: [PATCH 1/6] staging: android: binder: Remove some funny && usage

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Message-ID: <63386a3d0906241701o720fa667t662b9e3d4f080397@mail.gmail.com>
Date:	Thu, 25 Jun 2009 02:01:06 +0200
From:	Linus Walleij <linus.ml.walleij@...il.com>
To:	Brian Swetland <swetland@...gle.com>
Cc:	Daniel Walker <dwalker@...o99.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Greg Kroah-Hartman <greg@...ah.com>,
	linux-kernel@...r.kernel.org, hackbod@...roid.com
Subject: Re: [PATCH 1/6] staging: android: binder: Remove some funny && usage

2009/6/25 Brian Swetland <swetland@...gle.com>:
> 2009/6/24 Daniel Walker <dwalker@...o99.com>:
>> On Fri, 2009-06-19 at 17:13 -0700, Arve Hjønnevåg wrote:
>>>
>>> These are mostly questions for the framework team. The binder driver
>>> is there to support our user space code. At some point we used the
>>> driver from www.open-binder.org, but we ran into, and fixed, a lot of
>>> bugs (especially when processes died), so we determined it would be
>>> faster to rewrite the driver from scratch.
>>
>> Is there someone in your framework team that would be willing to respond
>> to these questions ? (I know you added hackbod to the CC, but they
>> aren't responding..)
>
> I guess it depends on the questions -- for good or ill, it's what is
> in use and replacing it with a different mechanism would be a pretty
> huge effort that there's unlikely to be time for in the near future.
> Quite a bit of the userspace framework depends on the binder handling
> the remote reference counting, object lifespan, etc, stuff and it's
> subtle and hairy to debug.  Moving to a different transport is
> possible (it's just software, as they say), but there's a lot of code
> that depends on the behavior that exists today.

What is nice about binder is that is steps in an fills the gap for rapid
buffer-passing IPC, is it really not possible to find common ground
with a D-Bus in-kernel IPC driver now that you're anyway using both
mechanisms and benefiting to both ends?

What I really want to know, is how this relates to the vmsplice() and
other zero-copy buffer passing schemes already in the kernel. I was
sort of dreaming that D-Bus and other IPC could be accelerated on
top of that.

Yours,
Linus Walleij
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