linux-kernel - Re: [PATCH v4 7/7] backlight: gpio: pull gpio_backlight_initial_power

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Message-ID: <20191002144028.6lljre76zxd52oui@holly.lan>
Date:   Wed, 2 Oct 2019 15:40:28 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jacopo Mondi <jacopo@...ndi.org>, linux-sh@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v4 7/7] backlight: gpio: pull
 gpio_backlight_initial_power_state() into probe

On Wed, Oct 02, 2019 at 01:46:17PM +0200, Bartosz Golaszewski wrote:
> śr., 2 paź 2019 o 12:33 Daniel Thompson <daniel.thompson@...aro.org> napisał(a):
> >
> > On Tue, Oct 01, 2019 at 02:58:37PM +0200, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > >
> > > The probe function in the gpio-backlight driver is quite short. If we
> > > pull gpio_backlight_initial_power_state() into probe we can drop two
> > > more fields from struct gpio_backlight and shrink the driver code.
> > >
> > > Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > > ---
> > >  drivers/video/backlight/gpio_backlight.c | 36 ++++++++----------------
> > >  1 file changed, 12 insertions(+), 24 deletions(-)
> > >
> > > diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c
> > > index 6247687b6330..37ec184f0c5c 100644
> > > --- a/drivers/video/backlight/gpio_backlight.c
> > > +++ b/drivers/video/backlight/gpio_backlight.c
> > > @@ -17,11 +17,8 @@
> > >  #include <linux/slab.h>
> > >
> > >  struct gpio_backlight {
> > > -     struct device *dev;
> > >       struct device *fbdev;
> > > -
> > >       struct gpio_desc *gpiod;
> > > -     int def_value;
> > >  };
> > >
> > >  static int gpio_backlight_update_status(struct backlight_device *bl)
> > > @@ -53,41 +50,24 @@ static const struct backlight_ops gpio_backlight_ops = {
> > >       .check_fb       = gpio_backlight_check_fb,
> > >  };
> > >
> > > -static int gpio_backlight_initial_power_state(struct gpio_backlight *gbl)
> >
> > I'm inclined to view deleting this function as removing a comment (e.g.
> > the function name helps us to read the code)!
> >
> 
> Right, but why not just add a comment then?

I guess you could add a comment but keeping it pulled out in a function
makes it easier to compare against equivalent code in other drivers
(such as pwm_bl).


Daniel.


> The probe function is 50
> lines long, there's really no need to split it. This will get inlined
> anyway too.
> 
> Bart
> 
> > Removing the variables from the context structure is good but why not
> > just pass them to the function and let the compiler decided whether or
> > not to inline.
> >
> >
> > Daniel.
> >
> >
> > > -{
> > > -     struct device_node *node = gbl->dev->of_node;
> > > -
> > > -     /* Not booted with device tree or no phandle link to the node */
> > > -     if (!node || !node->phandle)
> > > -             return gbl->def_value ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
> > > -
> > > -     /* if the enable GPIO is disabled, do not enable the backlight */
> > > -     if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
> > > -             return FB_BLANK_POWERDOWN;
> > > -
> > > -     return FB_BLANK_UNBLANK;
> > > -}
> > > -
> > > -
> > >  static int gpio_backlight_probe(struct platform_device *pdev)
> > >  {
> > >       struct device *dev = &pdev->dev;
> > >       struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
> > > +     struct device_node *of_node = dev->of_node;
> > >       struct backlight_properties props;
> > >       struct backlight_device *bl;
> > >       struct gpio_backlight *gbl;
> > > -     int ret;
> > > +     int ret, def_value;
> > >
> > >       gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
> > >       if (gbl == NULL)
> > >               return -ENOMEM;
> > >
> > > -     gbl->dev = dev;
> > > -
> > >       if (pdata)
> > >               gbl->fbdev = pdata->fbdev;
> > >
> > > -     gbl->def_value = device_property_read_bool(dev, "default-on");
> > > +     def_value = device_property_read_bool(dev, "default-on");
> > >
> > >       gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
> > >       if (IS_ERR(gbl->gpiod)) {
> > > @@ -109,7 +89,15 @@ static int gpio_backlight_probe(struct platform_device *pdev)
> > >               return PTR_ERR(bl);
> > >       }
> > >
> > > -     bl->props.power = gpio_backlight_initial_power_state(gbl);
> > > +     /* Not booted with device tree or no phandle link to the node */
> > > +     if (!of_node || !of_node->phandle)
> > > +             bl->props.power = def_value ? FB_BLANK_UNBLANK
> > > +                                         : FB_BLANK_POWERDOWN;
> > > +     else if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
> > > +             bl->props.power = FB_BLANK_POWERDOWN;
> > > +     else
> > > +             bl->props.power = FB_BLANK_UNBLANK;
> > > +
> > >       bl->props.brightness = 1;
> > >
> > >       backlight_update_status(bl);
> > > --
> > > 2.23.0
> > >