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

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Date: Mon, 26 Feb 2024 20:10:07 +0000
From: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To: "ojeda@...nel.org" <ojeda@...nel.org>, "robh+dt@...nel.org"
	<robh+dt@...nel.org>, "krzysztof.kozlowski+dt@...aro.org"
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	"lee@...nel.org" <lee@...nel.org>, "devicetree@...r.kernel.org"
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Subject: Re: [PATCH 0/3] auxdisplay: 7 segment LED display

Hi Alex,

On 27/02/24 05:04, Alexander Dahl wrote:
> Hello Chris,
>
> Am Mon, Feb 26, 2024 at 10:34:20AM +1300 schrieb Chris Packham:
>> 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).
>>
>> [1] - https://scanmail.trustwave.com/?c=20988&d=trbc5eARVo-5gepRnwbAKbQmiGk1bOSpqZDQx9bx7w&u=https%3a%2f%2flore%2ekernel%2eorg%2flkml%2f2a8d19ee-b18b-4b7c-869f-7d601cea30b6%40alliedtelesis%2eco%2enz%2f
> Read that thread out of curiosity and I'm sorry if I'm late to the
> party, but I wondered why this is limited to LEDs connected to GPIOs?
>
> Would it be possible to somehow stack this on top of some existing
> LEDs?  I mean you could wire a 7 segment device to almost any LED
> driver IC with enough channels, couldn't you?

Mainly because the GPIO version is the hardware I have. I do wonder how 
this might work with something like the pca9551 which really is just a 
fancy version of the pca9554 on my board. A naive implementation would 
be to configure all the pca9551 pins as GPIOs and use what I have as-is. 
Making a line display out of LED triggers might be another way of doing 
it but not something I really want to pursue.

>
> Greets
> Alex
>
>> Chris Packham (3):
>>    auxdisplay: Add 7 segment LED display driver
>>    dt-bindings: auxdisplay: Add bindings for generic 7 segment LED
>>    ARM: dts: marvell: Add 7 segment LED display on x530
>>
>>   .../auxdisplay/generic,gpio-7seg.yaml         |  40 +++++
>>   .../boot/dts/marvell/armada-385-atl-x530.dts  |  13 +-
>>   drivers/auxdisplay/Kconfig                    |   7 +
>>   drivers/auxdisplay/Makefile                   |   1 +
>>   drivers/auxdisplay/seg-led.c                  | 152 ++++++++++++++++++
>>   5 files changed, 212 insertions(+), 1 deletion(-)
>>   create mode 100644 Documentation/devicetree/bindings/auxdisplay/generic,gpio-7seg.yaml
>>   create mode 100644 drivers/auxdisplay/seg-led.c
>>
>> -- 
>> 2.43.2
>>
>>