Re: [PATCH v3 4/5] HID: mcp2221: switch i2c registration to devm functions

From: Matt Ranostay <matt.ranostay@konsulko.com>
To: Jonathan Cameron <jic23@kernel.org>
Cc: gupt21@gmail.com, linux-iio@vger.kernel.org,
	linux-input@vger.kernel.org, linux-i2c@vger.kernel.org
Subject: Re: [PATCH v3 4/5] HID: mcp2221: switch i2c registration to devm functions
Date: Sun, 18 Sep 2022 12:01:42 -0700	[thread overview]
Message-ID: <CAJCx=gkiHSyCUcU8+3+G8JMYoY4ucxFBOJojQUsRFGbipw7ZKQ@mail.gmail.com> (raw)
In-Reply-To: <20220918163933.0e52b581@jic23-huawei>

On Sun, Sep 18, 2022 at 8:39 AM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Mon, 12 Sep 2022 10:32:01 -0700
> Matt Ranostay <matt.ranostay@konsulko.com> wrote:
>
> > Switch from i2c_add_adapter() to resource managed devm_i2c_add_adapter()
> > for matching rest of driver initialization, and more concise code.
> >
> > Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
>
> This doesn't necessarily make things worse, but I'm not keen on the
> potential ordering issues that result form mixed devm / non-devm
> in this function.  It's too hard too think about!
>
> Easiest way to avoid people staring at the code to figure out if
> there are nasty issues would be to take the whole thing devm
> with a couple of devm_add_action_or_reset() to handle the
> hid_hw_stop()/hid_hw_close() at right points in the error / remove
> flows.

Good idea. Even if .remove() may be valid with the device resource
management it is a bit confusing.

- Matt

>
> Jonathan
>
>
> > ---
> >  drivers/hid/hid-mcp2221.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
> > index de52e9f7bb8c..29e69576c3d4 100644
> > --- a/drivers/hid/hid-mcp2221.c
> > +++ b/drivers/hid/hid-mcp2221.c
> > @@ -873,7 +873,7 @@ static int mcp2221_probe(struct hid_device *hdev,
> >                       "MCP2221 usb-i2c bridge on hidraw%d",
> >                       ((struct hidraw *)hdev->hidraw)->minor);
> >
> > -     ret = i2c_add_adapter(&mcp->adapter);
> > +     ret = devm_i2c_add_adapter(&hdev->dev, &mcp->adapter);
> >       if (ret) {
> >               hid_err(hdev, "can't add usb-i2c adapter: %d\n", ret);
> >               goto err_i2c;
> > @@ -884,7 +884,7 @@ static int mcp2221_probe(struct hid_device *hdev,
> >       mcp->gc = devm_kzalloc(&hdev->dev, sizeof(*mcp->gc), GFP_KERNEL);
> >       if (!mcp->gc) {
> >               ret = -ENOMEM;
> > -             goto err_gc;
> > +             goto err_i2c;
> >       }
> >
> >       mcp->gc->label = "mcp2221_gpio";
> > @@ -900,12 +900,10 @@ static int mcp2221_probe(struct hid_device *hdev,
> >
> >       ret = devm_gpiochip_add_data(&hdev->dev, mcp->gc, mcp);
> >       if (ret)
> > -             goto err_gc;
> > +             goto err_i2c;
> >
> >       return 0;
> >
> > -err_gc:
> > -     i2c_del_adapter(&mcp->adapter);
> >  err_i2c:
> >       hid_hw_close(mcp->hdev);
> >  err_hstop:
> > @@ -917,7 +915,6 @@ static void mcp2221_remove(struct hid_device *hdev)
> >  {
> >       struct mcp2221 *mcp = hid_get_drvdata(hdev);
> >
> > -     i2c_del_adapter(&mcp->adapter);
> >       hid_hw_close(mcp->hdev);
> >       hid_hw_stop(mcp->hdev);
> >  }
>