From: Heiner Kallweit <hkallweit1@gmail.com>
To: "Krzysztof Kozlowski" <krzk@kernel.org>,
"Robin Murphy" <robin.murphy@arm.com>,
"Rob Herring" <robh+dt@kernel.org>,
"Krzysztof Kozlowski" <krzysztof.kozlowski@canonical.com>,
"Andreas Färber" <afaerber@suse.de>,
"Miguel Ojeda" <ojeda@kernel.org>
Cc: "linux-spi@vger.kernel.org" <linux-spi@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"open list:ARM/Amlogic Meson..."
<linux-amlogic@lists.infradead.org>,
Jerome Brunet <jbrunet@baylibre.com>,
Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
Kevin Hilman <khilman@baylibre.com>,
Neil Armstrong <narmstrong@baylibre.com>,
Geert Uytterhoeven <geert+renesas@glider.be>
Subject: Re: [PATCH v5 2/6] dt-bindings: auxdisplay: Add Titan Micro Electronics TM1628
Date: Wed, 30 Mar 2022 07:54:29 +0200 [thread overview]
Message-ID: <5fde764f-4caf-8017-3cbd-3918f3390b6a@gmail.com> (raw)
In-Reply-To: <80937566-6455-b1bf-0a5d-a7b54dd3adc5@gmail.com>
On 23.03.2022 21:33, Heiner Kallweit wrote:
> On 21.03.2022 09:34, Krzysztof Kozlowski wrote:
>> On 18/03/2022 21:50, Robin Murphy wrote:
>>> On 2022-02-25 21:13, Heiner Kallweit wrote:
>>>> Add a YAML schema binding for TM1628 auxdisplay
>>>> (7/11-segment LED) controller.
>>>>
>>>> This patch is partially based on previous work from
>>>> Andreas Färber <afaerber@suse.de>.
>>>>
>>>> Co-developed-by: Andreas Färber <afaerber@suse.de>
>>>> Signed-off-by: Andreas Färber <afaerber@suse.de>
>>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>>>> ---
>>>> v5:
>>>> - add vendor prefix to driver-specific properties
>>>> ---
>>>> .../bindings/auxdisplay/titanmec,tm1628.yaml | 92 +++++++++++++++++++
>>>> 1 file changed, 92 insertions(+)
>>>> create mode 100644 Documentation/devicetree/bindings/auxdisplay/titanmec,tm1628.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/auxdisplay/titanmec,tm1628.yaml b/Documentation/devicetree/bindings/auxdisplay/titanmec,tm1628.yaml
>>>> new file mode 100644
>>>> index 000000000..2a1ef692c
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/auxdisplay/titanmec,tm1628.yaml
>>>> @@ -0,0 +1,92 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/auxdisplay/titanmec,tm1628.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: Titan Micro Electronics TM1628 LED controller
>>>> +
>>>> +maintainers:
>>>> + - Andreas Färber <afaerber@suse.de>
>>>> + - Heiner Kallweit <hkallweit1@gmail.com>
>>>> +
>>>> +allOf:
>>>> + - $ref: /schemas/spi/spi-peripheral-props.yaml#
>>>> +
>>>> +properties:
>>>> + compatible:
>>>> + const: titanmec,tm1628
>>>> +
>>>> + reg:
>>>> + maxItems: 1
>>>> +
>>>> + titanmec,grid:
>>>> + description:
>>>> + Mapping of display digit position to grid number.
>>>> + This implicitly defines the display size.
>>>> + $ref: /schemas/types.yaml#/definitions/uint8-array
>>>> + minItems: 1
>>>> + maxItems: 7
>>>> +
>>>> + titanmec,segment-mapping:
>>>> + description:
>>>> + Mapping of 7 segment display segments A-G to bit numbers 1-12.
>>>> + $ref: /schemas/types.yaml#/definitions/uint8-array
>>>> + minItems: 7
>>>> + maxItems: 7
>>>> +
>>>> + "#address-cells":
>>>> + const: 2
>>>> +
>>>> + "#size-cells":
>>>> + const: 0
>>>> +
>>>> +required:
>>>> + - compatible
>>>> + - reg
>>>
>>> Would it be fair to say that "spi-lsb-first" and "spi-3wire" are also
>>> required? The chips aren't configurable so won't exactly be usable any
>>> other way. Furthermore I believe the transmission format actually works
>>> out equivalent to SPI mode 3, so should warrant "spi-cpha" and
>>> "spi-cpol" as well.
>>>
>>>> +
>>>> +patternProperties:
>>>> + "^.*@[1-7],([1-9]|1[0-6])$":
>>>> + type: object
>>>> + $ref: /schemas/leds/common.yaml#
>>>> + unevaluatedProperties: false
>>>> + description: |
>>>> + Properties for a single LED.
>>>> +
>>>> + properties:
>>>> + reg:
>>>> + description: |
>>>> + 1-based grid number, followed by 1-based segment bit number.
>>>> + maxItems: 1
>>>> +
>>>> + required:
>>>> + - reg
>>>
>>> I'm concerned that this leaves us no room to support the additional
>>> keypad functionality in future. Having now double-checked a datasheet,
>>> the inputs are also a two-dimensional mux (sharing the segment lines),
>>> so the device effectively has two distinct but numerically-overlapping
>>> child address spaces - one addressed by (grid,segment) and the other by
>>> (segment,key).
>>>
>>> Rob, Krysztof, any thoughts on the best DT idiom to leave accommodation
>>> for that? I'm thinking either require an intermediate node to contain
>>> each notional address space, or perhaps add another leading address cell
>>> to select between them? I don't believe any of these things have further
>>> functionality beyond that.
>>
>> I think intermediate nodes - leds, keys - are more appropriate, because
>> it is self-describing. Additional address space number would require
>> decoding this "0" or "1" into LED/key. For complex devices - like PMICs
>> with regulators, RTC and clocks - we already have such patterns.
>>
> Then it's just the question who can implement such an intermediate node
> based on what has been done so far.
>
As it is now it seems we end up with empty hands again and have to wait
further two years for the next one to make an attempt.
That's a pity because for most users the relevant use cases are supported.
>> Best regards,
>> Best regards,
>> Krzysztof
>
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next prev parent reply other threads:[~2022-03-30 5:56 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-25 21:09 [PATCH v5 0/6] auxdisplay: Add support for the Titanmec TM1628 7 segment display controller Heiner Kallweit
2022-02-25 21:10 ` [PATCH v5 1/6] dt-bindings: vendor-prefixes: Add Titan Micro Electronics Heiner Kallweit
2022-02-25 21:13 ` [PATCH v5 2/6] dt-bindings: auxdisplay: Add Titan Micro Electronics TM1628 Heiner Kallweit
2022-03-04 23:07 ` Rob Herring
2022-03-18 20:50 ` Robin Murphy
2022-03-21 8:12 ` Geert Uytterhoeven
2022-04-19 22:31 ` Robin Murphy
2022-03-21 8:34 ` Krzysztof Kozlowski
2022-03-23 20:33 ` Heiner Kallweit
2022-03-30 5:54 ` Heiner Kallweit [this message]
2022-04-19 23:04 ` Robin Murphy
2022-04-20 16:27 ` Heiner Kallweit
2022-03-21 8:28 ` Krzysztof Kozlowski
2022-02-25 21:16 ` [PATCH v5 3/6] docs: ABI: document tm1628 attribute display_text Heiner Kallweit
2022-02-25 21:20 ` [PATCH v5 4/6] auxdisplay: add support for Titanmec TM1628 7 segment display controller Heiner Kallweit
2022-02-25 21:22 ` [PATCH v5 5/6] arm64: dts: meson-gxl-s905w-tx3-mini: add support for the 7 segment display Heiner Kallweit
2022-02-25 21:22 ` [PATCH v5 6/6] MAINTAINERS: Add entry for tm1628 auxdisplay driver Heiner Kallweit
2022-03-08 18:32 ` [PATCH v5 0/6] auxdisplay: Add support for the Titanmec TM1628 7 segment display controller Heiner Kallweit
2022-03-16 0:38 ` Robin Murphy
2022-03-16 21:19 ` Heiner Kallweit
2022-03-17 20:08 ` Robin Murphy
2022-03-17 21:49 ` Heiner Kallweit
2022-03-18 20:13 ` Robin Murphy
2022-04-23 20:57 ` Miguel Ojeda
2022-04-24 9:06 ` Heiner Kallweit
2022-05-12 12:46 ` Robin Murphy
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