linux-kernel - Re: [PATCH v6 3/9] backlight: gpio: explicitly set the direction of the GPIO

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Message-ID: <CAMRc=Md99q+67FAduiixQQs6BVtLXNrC=KbicsuBsB2Jp4O7dw@mail.gmail.com>
Date:   Mon, 21 Oct 2019 14:21:21 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Daniel Thompson <daniel.thompson@...aro.org>
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 list <linux-sh@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v6 3/9] backlight: gpio: explicitly set the direction of
 the GPIO

pon., 21 paź 2019 o 12:45 Daniel Thompson <daniel.thompson@...aro.org>
napisał(a):
>
> On Sat, Oct 19, 2019 at 10:35:50AM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> > The GPIO backlight driver currently requests the line 'as is', without
> > acively setting its direction. This can lead to problems: if the line
> > is in input mode by default, we won't be able to drive it later when
> > updating the status and also reading its initial value doesn't make
> > sense for backlight setting.
> >
> > Request the line 'as is' initially, so that we can read its value
> > without affecting it but then change the direction to output explicitly
> > when setting the initial brightness.
> >
> > Also: check the current direction and only read the value if it's output.
> >
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>
> Intent looks good to me but...
>
> > ---
> >  drivers/video/backlight/gpio_backlight.c | 23 ++++++++++++++++++-----
> >  1 file changed, 18 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c
> > index 3955b513f2f8..a36ac3a45b81 100644
> > --- a/drivers/video/backlight/gpio_backlight.c
> > +++ b/drivers/video/backlight/gpio_backlight.c
> > @@ -25,9 +25,8 @@ struct gpio_backlight {
> >       int def_value;
> >  };
> >
> > -static int gpio_backlight_update_status(struct backlight_device *bl)
> > +static int gpio_backlight_get_curr_brightness(struct backlight_device *bl)
>
> This function does not get the current brightness (e.g. what the
> hardware is currently doing). Given we've just nuked the function that
> *did* get the current brightness from the hardware this isn't an
> acceptable name.
>
> Would like something like calc_brightness() or get_next_brightness().
>

Fair enough, the latter sounds good in this case.

Bart