linux-kernel - Re: [PATCH] mbox: qcom: avoid unused-variable warning

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Message-Id: <20190927182604.79F3E217D7@mail.kernel.org>
Date:   Fri, 27 Sep 2019 11:26:03 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Andy Gross <agross@...nel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mbox: qcom: avoid unused-variable warning

Quoting Geert Uytterhoeven (2019-09-26 06:07:13)
> Hi Stephen,
> 
> On Fri, Sep 20, 2019 at 11:06 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > Quoting Arnd Bergmann (2019-09-20 12:27:50)
> > > On Fri, Sep 20, 2019 at 6:45 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > > > > @@ -54,11 +60,6 @@ static int qcom_apcs_ipc_probe(struct platform_device *pdev)
> > > > >         void __iomem *base;
> > > > >         unsigned long i;
> > > > >         int ret;
> > > > > -       const struct of_device_id apcs_clk_match_table[] = {
> > > >
> > > > Does marking it static here work too? It would be nice to limit the
> > > > scope of this variable to this function instead of making it a global.
> > > > Also, it might be slightly smaller code size if that works.
> > >
> > > No, I just tried and the warning returned.
> 
> It's there for the convenience for the user, so he doesn't have to add it
> himself explicitly.
> 
> > ("of/device: Nullify match table in of_match_device() for CONFIG_OF=n"),
> > but it's been 5 years! Surely we can revert this change now that commit
> > 219a7bc577e6 ("spi: rspi: Use of_device_get_match_data() helper") is
> > merged.
> 
> Right, the particular error case in the RSPI driver can no longer happen.
> 
> Calling of_device_get_match_data() is the better solution anyway, as
> that uses the match table stored in dev->driver->of_match_table, so
> there's no need to pass the table explicitly, and conditionally.
> 
> Hence...
> 
> > --- a/drivers/leds/leds-pca9532.c
> > +++ b/drivers/leds/leds-pca9532.c
> > @@ -472,7 +472,7 @@ pca9532_of_populate_pdata(struct device *dev, struct device_node *np)
> >         int i = 0;
> >         const char *state;
> >
> > -       match = of_match_device(of_pca9532_leds_match, dev);
> > +       match = of_match_device(of_match_ptr(of_pca9532_leds_match), dev);
> >         if (!match)
> >                 return ERR_PTR(-ENODEV);
> 
> Please convert to of_device_get_match_data() instead of adding
> of_match_ptr() invocations...

How is this workable? I left it as of_match_device() because the value
returned may be 0 for the enum and that looks the same as NULL.

> 
> > @@ -525,7 +525,7 @@ static int pca9532_probe(struct i2c_client *client,
> >                         dev_err(&client->dev, "no platform data\n");
> >                         return -EINVAL;
> >                 }
> > -               of_id = of_match_device(of_pca9532_leds_match,
> > +               of_id = of_match_device(of_match_ptr(of_pca9532_leds_match),
> 
> Likewise.
> 
> > --- a/sound/soc/jz4740/jz4740-i2s.c
> > +++ b/sound/soc/jz4740/jz4740-i2s.c
> > @@ -503,7 +503,7 @@ static int jz4740_i2s_dev_probe(struct platform_device *pdev)
> >         if (!i2s)
> >                 return -ENOMEM;
> >
> > -       match = of_match_device(jz4740_of_matches, &pdev->dev);
> > +       match = of_match_device(of_match_ptr(jz4740_of_matches), &pdev->dev);
> 
> Given of_device_get_match_data() returns NULL, not an error code, even
> this one could use of_device_get_match_data().
>