linux-kernel - Re: [RFC PATCH] ALSA: core: Add DMA share buffer support

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Message-ID: <CAMz4ku+eiqPAETMhGJ3=fQKfzJEORvjmr+51-oJZ5B5AyQcvkw@mail.gmail.com>
Date:   Mon, 28 Jan 2019 13:48:22 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Leo Yan <leo.yan@...aro.org>,
        Mark Brown <broonie@...nel.org>, alsa-devel@...a-project.org,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>, bgoswami@...eaurora.org,
        sr@...x.de, gustavo@...eddedor.com,
        Phil Burk <philburk@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        mchehab+samsung@...nel.org, sboyd@...nel.org,
        Vinod Koul <vkoul@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        anna-maria@...utronix.de, Jon Corbet <corbet@....net>,
        Jeffery Miller <jmiller@...erware.com>,
        Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
        joe@...ches.com, Takashi Sakamoto <o-takashi@...amocchi.jp>,
        colyli@...e.de, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] ALSA: core: Add DMA share buffer support

On Fri, 25 Jan 2019 at 21:04, Takashi Iwai <tiwai@...e.de> wrote:
> > >
> > > Erm, obviously it's not enough.  Each attach / detach needs to manage
> > > the refcount, too, for covering the cases above.  It can re-use the
> > > PCM mmap_refount, though.
> >
> > But we've used the DMA buffer file's refcounting to manage the DMA
> > buffer. So is this not enough?
>
> Unless you manage the PCM substream refcount (or block the state
> change), the PCM stream itself can be released (or re-setup) freely.
>

OK. Thanks for your comments.

-- 
Baolin Wang
Best Regards