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

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Message-ID: <20230501172502.125e4859@jic23-huawei>
Date:   Mon, 1 May 2023 17:25:02 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
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

On Tue, 18 Apr 2023 10:08:21 +0200
Paul Cercueil <paul@...pouillou.net> wrote:

> 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.

Remind me of that in the cover letter for v4.

Thanks,

Jonathan

> 
> Cheers,
> -Paul