linux-kernel - Re: [PATCH v4 19/19] auxdisplay: ht16k33: Add LED support

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Message-ID: <CAMuHMdVdB3spJxZ5QVdSV0j8ZxNSZDjcX5B_kGitxyLLdyCwLg@mail.gmail.com>
Date:   Wed, 28 Jul 2021 09:39:15 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Robin van der Gracht <robin@...tonic.nl>,
        Rob Herring <robh+dt@...nel.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Paul Burton <paulburton@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@....cz>, Marek Behun <marek.behun@....cz>,
        Arnd Bergmann <arnd@...db.de>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-leds <linux-leds@...r.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 19/19] auxdisplay: ht16k33: Add LED support

Hi Randy,

On Tue, Jul 27, 2021 at 11:05 PM Randy Dunlap <rdunlap@...radead.org> wrote:
> On 7/27/21 7:04 AM, Geert Uytterhoeven wrote:
> > Instantiate a single LED based on the "led" subnode in DT.
> > This allows the user to control display brightness and blinking (backed
> > by hardware support) through the LED class API and triggers, and exposes
> > the display color.  The LED will be named
> > "auxdisplay:<color>:<function>".
> >
> > When running in dot-matrix mode and if no "led" subnode is found, the
> > driver falls back to the traditional backlight mode, to preserve
> > backwards compatibility.
> >
> > Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > ---
> > v4:
> >   - Add missing select LEDS_CLASS,

> Since LEDS_CLASS depends on NEW_LEDS, does this also need to
> select NEW_LEDS?

Right, I missed that.  It needs to select both NEW_LEDS and LED_CLASS.
Do I need to resend the whole series, or can this be fixed while
applying?

> and similar for INPUT_MATRIXKMAP: it depends on INPUT.

HT16K33 already depends on INPUT.

> However, selecting (enabling) an entire subsystem is not a
> preferable thing to do.

Unfortunately we have no choice, unless we untangle the depends/select
web first:

HT16K33 depends on NEW_LEDS, select LEDS_CLASS:

    drivers/leds/Kconfig:9:error: recursive dependency detected!
    drivers/leds/Kconfig:9:     symbol NEW_LEDS is selected by SENSORS_APPLESMC
    drivers/hwmon/Kconfig:324:  symbol SENSORS_APPLESMC depends on HWMON
    drivers/hwmon/Kconfig:6:    symbol HWMON is selected by EEEPC_LAPTOP
    drivers/platform/x86/Kconfig:305:   symbol EEEPC_LAPTOP depends on
ACPI_VIDEO

HT16K33 depends on LEDS_CLASS:

    drivers/leds/Kconfig:17:error: recursive dependency detected!
    drivers/leds/Kconfig:17:    symbol LEDS_CLASS depends on NEW_LEDS
    drivers/leds/Kconfig:9:     symbol NEW_LEDS is selected by SENSORS_APPLESMC
    drivers/hwmon/Kconfig:324:  symbol SENSORS_APPLESMC depends on HWMON
    drivers/hwmon/Kconfig:6:    symbol HWMON is selected by EEEPC_LAPTOP
    drivers/platform/x86/Kconfig:305:   symbol EEEPC_LAPTOP depends on
ACPI_VIDEO

> > --- a/drivers/auxdisplay/Kconfig
> > +++ b/drivers/auxdisplay/Kconfig
> > @@ -176,6 +176,7 @@ config HT16K33
> >       select FB_SYS_IMAGEBLIT
> >       select INPUT_MATRIXKMAP
> >       select FB_BACKLIGHT
> > +     select LEDS_CLASS
> >       select LINEDISP
> >       help
> >         Say yes here to add support for Holtek HT16K33, RAM mapping 16*8

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds