linux-kernel - Re: [PATCH 3/6] iio: imx7d_adc: Use devm_iio_device

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Date:   Sat, 13 Apr 2019 18:04:08 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     linux-iio@...r.kernel.org, Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Chris Healy <cphealy@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/6] iio: imx7d_adc: Use devm_iio_device_register()

On Sun, Apr 7, 2019 at 4:07 AM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Wed,  3 Apr 2019 00:03:22 -0700
> Andrey Smirnov <andrew.smirnov@...il.com> wrote:
>
> > Use devm_iio_device_register() and drop explicit call to
> > iio_device_unregister().
> >
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> > Cc: Jonathan Cameron <jic23@...nel.org>
> > Cc: Hartmut Knaack <knaack.h@....de>
> > Cc: Lars-Peter Clausen <lars@...afoo.de>
> > Cc: Peter Meerwald-Stadler <pmeerw@...erw.net>
> > Cc: Chris Healy <cphealy@...il.com>
> > Cc: linux-iio@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> No to this one.  The thing to think about is the resulting order
> of the unwinding that happens in remove.
>
> Do take a look at the code flow, but in short what happens is:
>
> 1. driver.remove()
> 2. Devm release functions run in the opposite order to they were
>    called during setup.
>
> The upshot of the change you just made here is that we turn the power
> off to the device before we remove the userspace interfaces, giving
> potentially interesting failures..
>
> There are two options to avoid this:
>
> 1. Make everything use devm_ calls (often using devm_add_action_or_reset
> for the ones that don't have their own versions).
>
> 2. Stop using devm managed functions at the first non devm_ call that needs
> unwinding.  From that point onwards in probe / remove you have to do everything
> manually.
>

Yeah, missed the ordering proble, sorry about that. I'll re-order
changes such that this conversion happens last to avoid said problem
in v2.

Thanks,
Andrey Smirnov