Received-SPF: pass (google.com: domain of linux-kernel+bounces-77888-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Precedence: bulk
MIME-Version: 1.0
References: <1f598a72-dd9f-4c6c-af7f-29751f84bd23@alliedtelesis.co.nz>
 <Zde966nsJ76QOuzm@surfacebook.localdomain> <f5e74774-226a-4678-a6f9-b4f17250ad91@alliedtelesis.co.nz>
 <CAHp75Vfq3Pc+Eo3Z5mhORZwwuKF+Y7_47dTO8qARcfba4nmj2w@mail.gmail.com>
 <9d00e1b1-120b-4c2b-89c5-0ac736bf6441@alliedtelesis.co.nz>
 <CAHp75VdnXtVwrLrcGjnYMfNx7roBvQm9DMr6_ndjZeAbRDbs_Q@mail.gmail.com>
 <2a8d19ee-b18b-4b7c-869f-7d601cea30b6@alliedtelesis.co.nz> <ZdhNlUotGJCklJTs@duo.ucw.cz>
In-Reply-To: <ZdhNlUotGJCklJTs@duo.ucw.cz>
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Fri, 23 Feb 2024 08:53:01 +0100
Message-ID: <CAMuHMdVPcty_O5uwTv6eBNwt_PNviKwjpjmfiOF05tqNW_CA4g@mail.gmail.com>
Subject: Re: Linux support for a 7 segment LED display
To: Pavel Machek <pavel@ucw.cz>
Cc: Chris Packham <Chris.Packham@alliedtelesis.co.nz>, 
	Andy Shevchenko <andy.shevchenko@gmail.com>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, "lee@kernel.org" <lee@kernel.org>, 
	"linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>, 
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Hi Pavel,

On Fri, Feb 23, 2024 at 8:47=E2=80=AFAM Pavel Machek <pavel@ucw.cz> wrote:
> > > Right, but also with some additional properties, like
> > > - type of the indicator (7, 14, etc segments, for now we have only
> > > these two supported)
> > > - use-dot (+1 led per each digit)
> > > - characters (how many digits we have, so we need respective amount o=
f GPIOs)
> > >
> > > With this it's indeed belongs directly to auxdisplay as we have almos=
t
> > > everything is done already there.
> >
> > I've been playing about with this. I've got an auxdisplay driver that's
> > basically working (I won't bother spamming list with it yet). But I'm
> > wondering how I'd represent multiple characters. I kind of feel the
> > natural representation would be something like.
> >
> >          led-7seg {
> >                  compatible =3D "generic,7-segment-on-gpio";
> >                  char-0 {
> >                      segment-gpios =3D <&gpio 0 GPIO_ACTIVE_LOW
> >                                       &gpio 1 GPIO_ACTIVE_LOW
> >                                       &gpio 2 GPIO_ACTIVE_LOW
> >                                       &gpio 3 GPIO_ACTIVE_LOW
> >                                       &gpio 4 GPIO_ACTIVE_LOW
> >                                       &gpio 5 GPIO_ACTIVE_LOW
> >                                       &gpio 6 GPIO_ACTIVE_LOW>;
> >                  };
> >                  char-1 {
> >                      segment-gpios =3D <&gpio 8 GPIO_ACTIVE_LOW
> >                                       &gpio 9 GPIO_ACTIVE_LOW
> >                                       &gpio 10 GPIO_ACTIVE_LOW
> >                                       &gpio 11 GPIO_ACTIVE_LOW
> >                                       &gpio 12 GPIO_ACTIVE_LOW
> >                                       &gpio 13 GPIO_ACTIVE_LOW
> >                                       &gpio 14 GPIO_ACTIVE_LOW>;
> >                  };
> >          };
> >
> > But having those sub-nodes means I can't just use devm_gpiod_get_array(=
)
> > instead I'd have to use device_for_each_child_node() and
> > devm_fwnode_gpiod_get_index(). Am I missing something? I could do away
> > with the sub-nodes and have properties like "segment-0-gpios",
> > "segment-1-gpios" but that feels awkward.
>
> One solution would be to treat separate digits as separata devices
> :-).

That's definitely an option, but would prevent you from having a
single display using auxdisplay/line-display.

> Other would be saying you don't have hardware for that, and make it
> someone else's future problem.

;-)

Gr{oetje,eeting}s,

                        Geert

--=20
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k=
org

In personal conversations with technical people, I call myself a hacker. Bu=
t
when I'm talking to journalists I just say "programmer" or something like t=
hat.
                                -- Linus Torvalds