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From:   Baolin Wang <baolin.wang@linaro.org>
Date:   Mon, 28 Jan 2019 13:48:22 +0800
Message-ID: <CAMz4ku+eiqPAETMhGJ3=fQKfzJEORvjmr+51-oJZ5B5AyQcvkw@mail.gmail.com>
Subject: Re: [RFC PATCH] ALSA: core: Add DMA share buffer support
To:     Takashi Iwai <tiwai@suse.de>
Cc:     Jaroslav Kysela <perex@perex.cz>, Leo Yan <leo.yan@linaro.org>,
        Mark Brown <broonie@kernel.org>, alsa-devel@alsa-project.org,
        Arnd Bergmann <arnd@arndb.de>,
        Kees Cook <keescook@chromium.org>, bgoswami@codeaurora.org,
        sr@denx.de, gustavo@embeddedor.com,
        Phil Burk <philburk@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        mchehab+samsung@kernel.org, sboyd@kernel.org,
        Vinod Koul <vkoul@kernel.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        anna-maria@linutronix.de, Jon Corbet <corbet@lwn.net>,
        Jeffery Miller <jmiller@neverware.com>,
        Charles Keepax <ckeepax@opensource.wolfsonmicro.com>,
        joe@perches.com, Takashi Sakamoto <o-takashi@sakamocchi.jp>,
        colyli@suse.de, LKML <linux-kernel@vger.kernel.org>
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On Fri, 25 Jan 2019 at 21:04, Takashi Iwai <tiwai@suse.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