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Date: Fri, 11 Mar 2016 03:17:14 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Christoph Hellwig <hch@infradead.org>,
        Ulf Hansson <ulf.hansson@linaro.org>, Tejun Heo <tj@kernel.org>,
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Subject: Re: [PATCH RFC 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O
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On Sat, Mar 05, 2016 at 07:18:30PM +0700, Linus Walleij wrote:
> Depends on what time horizon and target I'd say. Paolo was in contact with
> the MMC/SD subsystem maintainer Ulf Hansson. (e)MMC/SD are both
> synchronous command-response-based protocols, and as of today
> single-channel. So everone's smartphone and tablet etc are today
> single-channel. I don't know if there is even a protocol change coming
> to augment this, the only duct-tapeish solution I've heard about is
> command queueing which is basically a kind of pipelining of requests.

We use blkj-mq for single queue devices as well, in fact most consumers
are single queue.  MMC is a prime candidate that hould move over soon.