linux-kernel - Re: [PATCH v3 03/11] iio: buffer-dma: Get rid of outgoing queue

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Message-ID: <1f63ffced9ed18309401af9a885310e1715b6538.camel@crapouillou.net>
Date:   Tue, 18 Apr 2023 10:08:21 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Vinod Koul <vkoul@...nel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Nuno Sá <noname.nuno@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v3 03/11] iio: buffer-dma: Get rid of outgoing queue

Hi Jonathan,

Le dimanche 16 avril 2023 à 15:24 +0100, Jonathan Cameron a écrit :
> On Mon,  3 Apr 2023 17:47:52 +0200
> Paul Cercueil <paul@...pouillou.net> wrote:
> 
> > The buffer-dma code was using two queues, incoming and outgoing, to
> > manage the state of the blocks in use.
> > 
> > While this totally works, it adds some complexity to the code,
> > especially since the code only manages 2 blocks. It is much easier
> > to
> > just check each block's state manually, and keep a counter for the
> > next
> > block to dequeue.
> > 
> > Since the new DMABUF based API wouldn't use the outgoing queue
> > anyway,
> > getting rid of it now makes the upcoming changes simpler.
> > 
> > With this change, the IIO_BLOCK_STATE_DEQUEUED is now useless, and
> > can
> > be removed.
> > 
> > Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> > 
> > ---
> > v2: - Only remove the outgoing queue, and keep the incoming queue,
> > as we
> >       want the buffer to start streaming data as soon as it is
> > enabled.
> >     - Remove IIO_BLOCK_STATE_DEQUEUED, since it is now functionally
> > the
> >       same as IIO_BLOCK_STATE_DONE.
> 
> I'm not that familiar with this code, but with my understanding this
> makes
> sense.   I think it is independent of the earlier patches and is a
> useful
> change in it's own right.  As such, does it make sense to pick this
> up
> ahead of the rest of the series? I'm assuming that discussion on the
> rest will take a while.  No great rush as too late for the coming
> merge
> window anyway.

Actually, you can pick patches 3 to 6 (when all have been acked). They
add write support for buffer-dma implementations; which is a dependency
for the rest of the patchset, but they can live on their own.

Cheers,
-Paul