linux-kernel - Re: [PATCH v10 1/5] serdev: Make .remove in struct serdev_device

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Message-ID: <20171104170548.vkkgp363k2piyufx@earth>
Date:   Sat, 4 Nov 2017 18:05:48 +0100
From:   Sebastian Reichel <sebastian.reichel@...labora.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        Rob Herring <robh@...nel.org>, cphealy@...il.com,
        Guenter Roeck <linux@...ck-us.net>,
        Lucas Stach <l.stach@...gutronix.de>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Lee Jones <lee.jones@...aro.org>, Pavel Machek <pavel@....cz>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH v10 1/5] serdev: Make .remove in struct
 serdev_device_driver optional

Hi Greg,

On Sat, Nov 04, 2017 at 12:24:31PM +0100, Greg Kroah-Hartman wrote:
> On Tue, Oct 31, 2017 at 09:36:52AM -0700, Andrey Smirnov wrote:
> > Using devres infrastructure it is possible to write a serdev driver
> > that doesn't have any code that needs to be called as a part of
> > .remove. Add code to make .remove optional.
> 
> What about manual unbind from userspace through sysfs?  You need to have
> a remove function.  All drivers need that, to not have it is pretty lazy :)

Resources,that have been requested via devres are free'd by the
devres framework after the driver specific remove function. This
also works for manual unbind.

If *all* driver resources are allocated using devres, you will end
up with an empty remove function. In that case it makes sense to
remove it completly. This is what quite a few (mainline) i2c and
spi drivers actually do.

-- Sebastian

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