linux-kernel - Re: [PATCH 0/3] auxdisplay: 7 segment LED display

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Message-ID: <CAHp75Vc3NFULXByhAv=1bq0aPsbH+_zVypQwaDGNrtafj+xGaw@mail.gmail.com>
Date: Tue, 27 Feb 2024 02:58:23 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc: "ojeda@...nel.org" <ojeda@...nel.org>, "robh+dt@...nel.org" <robh+dt@...nel.org>, 
	"krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>, 
	"conor+dt@...nel.org" <conor+dt@...nel.org>, "andrew@...n.ch" <andrew@...n.ch>, 
	"gregory.clement@...tlin.com" <gregory.clement@...tlin.com>, 
	"sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>, 
	"geert@...ux-m68k.org" <geert@...ux-m68k.org>, "pavel@....cz" <pavel@....cz>, "lee@...nel.org" <lee@...nel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, 
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>
Subject: Re: [PATCH 0/3] auxdisplay: 7 segment LED display

On Tue, Feb 27, 2024 at 2:52 AM Chris Packham
<Chris.Packham@...iedtelesis.co.nz> wrote:
> On 26/02/24 15:23, Andy Shevchenko wrote:
> > On Sun, Feb 25, 2024 at 11:34 PM Chris Packham
> > <chris.packham@...iedtelesis.co.nz> wrote:
> >> This series adds a driver for a 7 segment LED display.
> >>
> >> I'd like to get some feedback on how this could be extended to support >1
> >> character. The driver as presented is sufficient for my hardware which only has
> >> a single character display but I can see that for this to be generically useful
> >> supporting more characters would be desireable.
> >>
> >> Earlier I posted an idea that the characters could be represended by
> >> sub-nodes[1] but there doesn't seem to be a way of having that and keeping the
> >> convenience of using devm_gpiod_get_array() (unless I've missed something).
> > It seems you didn't know that the tree for auxdisplay has been changed.
> > Can you rebase your stuff on top of
> > https://scanmail.trustwave.com/?c=20988&d=vfbb5fnU59kvIREfdD-21Pab30bpMpuTM2Ipv28now&u=https%3a%2f%2fgit%2ekernel%2eorg%2fpub%2fscm%2flinux%2fkernel%2fgit%2fandy%2flinux-auxdisplay%2egit%2flog%2f%3fh%3dfor-next%3f
> > It will reduce your code base by ~50%.
> >
> > WRT subnodes, you can go with device_for_each_child_node() and
> > retrieve gpio array per digit. It means you will have an array of
> > arrays of GPIOs.
>
> So would the following work?
>
>      count = device_get_child_node_count(dev);
>      struct gpio_descs **chars  = devm_kzalloc(dev, sizeof(*chars) *
> count, GFP_KERNEL);
>
>      i = 0;
>      device_for_each_child_node(dev, child) {
>          chars[i] = devm_gpiod_get_array(dev, "segment", GPIOD_OUT_LOW);

I see what you meant earlier.
This should be devm_fwnode_gpiod_get_index(), but we lack the _array
variant of it...

Dunno what to do, maybe adding the _array variant is the good move,
maybe something else.

>      }
>
> I haven't used the child. The devm_gpiod_get_array() will be looking at
> the fwnode of the parent.


-- 
With Best Regards,
Andy Shevchenko