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Date:   Fri, 27 Sep 2019 00:38:49 +0200
From:   Lukasz Majewski <lukma@denx.de>
To:     Mark Brown <broonie@kernel.org>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Colin Ian King <colin.king@canonical.com>,
        linux-spi <linux-spi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: spi: Add call to spi_slave_abort() function when spidev driver
 is released
Message-ID: <20190927003849.0c9e4335@jawa>
In-Reply-To: <20190926151752.GU2036@sirena.org.uk>
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Hi Mark, Geert,

> On Thu, Sep 26, 2019 at 04:06:45PM +0200, Lukasz Majewski wrote:
> > > On Thu, Sep 26, 2019 at 2:49 PM Lukasz Majewski <lukma@denx.de>
> > > wrote: =20
>=20
> > > > The question is if we shall call the spi_slave_abort() when
> > > > cleaning up spi after releasing last reference, or each time
> > > > release callback is called ?   =20
>=20
> > > TBH, I don't know.  Is it realistic that there are multiple
> > > opens? =20
>=20
> > I'm using on my setup only one test program to use /dev/spidevX.Y
> > and /dev/spidevA.B (loopback with wired connection). =20
>=20
> > However, you also shall be able to connect via ssh and run the same
> > setup in parallel... =20
>=20
> It doesn't seem entirely realistic, but I can imagine cases like
> fork()/exec() where we end up with two copies of the file open
> but end up immediately closing one.
>=20
> > > That means the abort is called only for the last user.
> > > And only if the underlying device still exists.  Which means that
> > > if it has disappeared (how can that happen? spidev unbind?), =20
>=20
> > In my case, I just disconnect some SPI signals and the test program
> > just hangs. I do need to ctrl+c to stop it (or use timeout).  =20
>=20
> > From my debugging the .release callback is called each time the
> > program is aborted (either with ctrl+c or timeout). =20
>=20
> Should be on file close IIRC.

Any ideas on how to solve this issue?

Maybe, it would be sufficient for now to move the spi_slave_abort() in
spi_release() before we decrease (spidev->users--) the use count?


Best regards,

Lukasz Majewski

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