linux-kernel - Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver

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Message-ID: <CAK8P3a3OBUZC2nxaQ2wyL9EeT3gzXUX9sfJ+ZJfJUiJK_3ZkrA@mail.gmail.com>
Date:   Tue, 23 Mar 2021 10:27:58 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Jie Deng <jie.deng@...el.com>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Linux I2C <linux-i2c@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Wolfram Sang <wsa@...nel.org>,
        Jason Wang <jasowang@...hat.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        conghui.chen@...el.com, kblaiech@...lanox.com,
        jarkko.nikula@...ux.intel.com,
        Sergey Semin <Sergey.Semin@...kalelectronics.ru>,
        Mike Rapoport <rppt@...nel.org>, loic.poulain@...aro.org,
        Tali Perry <tali.perry1@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        yu1.wang@...el.com, shuo.a.liu@...el.com,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver

On Tue, Mar 23, 2021 at 9:33 AM Jie Deng <jie.deng@...el.com> wrote:
>
> On 2021/3/23 15:27, Viresh Kumar wrote:
>
> > On 23-03-21, 22:19, Jie Deng wrote:
> >> +static int __maybe_unused virtio_i2c_freeze(struct virtio_device *vdev)
> >> +{
> >> +    virtio_i2c_del_vqs(vdev);
> >> +    return 0;
> >> +}
> >> +
> >> +static int __maybe_unused virtio_i2c_restore(struct virtio_device *vdev)
> >> +{
> >> +    return virtio_i2c_setup_vqs(vdev->priv);
> >> +}
> > Sorry for not looking at this earlier, but shouldn't we enclose the above two
> > within #ifdef CONFIG_PM_SLEEP instead and drop the __maybe_unused ?
>
>
> I remembered I was suggested to use "__maybe_unused" instead of "#ifdef".
>
> You may check this https://lore.kernel.org/patchwork/patch/732981/
>
> The reason may be something like that.

I usually recommend the use of __maybe_unused for the suspend/resume
callbacks for drivers that use SIMPLE_DEV_PM_OPS() or similar helpers
that hide the exact conditions under which the functions get called.

In this driver, there is an explicit #ifdef in the reference to the
functions, so
it would make sense to use the same #ifdef around the definition.

A better question to ask is whether you could use the helpers instead,
and drop the other #ifdef.

       Arnd