Re: [PATCH 3/6] iio: imx7d_adc: Use devm_iio_device_register()

[Andrey Smirnov]

On Sun, Apr 7, 2019 at 4:07 AM Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
>
> On Wed,  3 Apr 2019 00:03:22 -0700
> Andrey Smirnov <andrew.smirnov@xxxxxxxxx> wrote:
>
> > Use devm_iio_device_register() and drop explicit call to
> > iio_device_unregister().
> >
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
> > Cc: Jonathan Cameron <jic23@xxxxxxxxxx>
> > Cc: Hartmut Knaack <knaack.h@xxxxxx>
> > Cc: Lars-Peter Clausen <lars@xxxxxxxxxx>
> > Cc: Peter Meerwald-Stadler <pmeerw@xxxxxxxxxx>
> > Cc: Chris Healy <cphealy@xxxxxxxxx>
> > Cc: linux-iio@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> 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