linux-kernel - Re: spi: Add call to spi_slave_abort() function when spidev driver is released

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Message-ID: <20190926151752.GU2036@sirena.org.uk>
Date:   Thu, 26 Sep 2019 08:17:52 -0700
From:   Mark Brown <broonie@...nel.org>
To:     Lukasz Majewski <lukma@...x.de>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Colin Ian King <colin.king@...onical.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: spi: Add call to spi_slave_abort() function when spidev driver
 is released

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@...x.de> wrote:

> > > 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 ?  

> > TBH, I don't know.  Is it realistic that there are multiple opens?

> I'm using on my setup only one test program to use /dev/spidevX.Y and
> /dev/spidevA.B (loopback with wired connection).

> However, you also shall be able to connect via ssh and run the same
> setup in parallel...

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.

> > 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?),

> 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). 

> From my debugging the .release callback is called each time the program
> is aborted (either with ctrl+c or timeout).

Should be on file close IIRC.

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