Re: [PATCH v5 0/6] auxdisplay: Add support for the Titanmec TM1628 7 segment display controller

[Heiner Kallweit <hkallweit1@xxxxxxxxx>]

On 16.03.2022 01:38, Robin Murphy wrote:
> On 2022-02-25 21:09, Heiner Kallweit wrote:
>> This series adds support for the Titanmec TM1628 7 segment display
>> controller. It's based on previous RFC work from Andreas Färber.
>> The RFC version placed the driver in the LED subsystem, but this was
>> NAK'ed by the LED maintainer. Therefore I moved the driver to
>> /drivers/auxdisplay what seems most reasonable to me.
>>
>> Further changes to the RFC version:
>> - Driver can be built also w/o LED class support, for displays that
>>    don't have any symbols to be exposed as LED's.
>> - Simplified the code and rewrote a lot of it.
>> - Driver is now kind of a MVP, but functionality should be sufficient
>>    for most use cases.
>> - Use the existing 7 segment support in uapi/linux/map_to_7segment.h
>>    as suggested by Geert Uytterhoeven.
>>
>> Note: There's a number of chips from other manufacturers that are
>>        almost identical, e.g. FD628, SM1628. Only difference I saw so
>>        far is that they partially support other display modes.
>>        TM1628: 6x12, 7x11
>>        SM1628C: 4x13, 5x12, 6x11, 7x10
>>        For typical displays on devices using these chips this
>>        difference shouldn't matter.
>>
>> Successfully tested on a TX3 Mini TV box that has an SM1628C and a
>> display with 4 digits and 7 symbols.
> 
> FWIW I gave this a go on my Beelink A1, which has an AiP1618 and a clock display which would mapped like so:
> 
>     titanmec,segment-mapping = /bits/ 8 <1 2 3 13 12 5 4>;
>     titanmec,grid = /bits/ 8 <5 4 2 1>;
> 
> (grid 3 segment 2 is used for a colon in the middle)
> 
> If I bodge around the lack of support for non-contiguous grids, it does otherwise work fairly well, other than being 6-segment displays because it needs to be in display mode 1 to drive SEG13 rather than GRID6. I wonder if we could be a bit cleverer about picking a display mode based on the grid/segment numbers used?
> 
Definitely this could be one future extension. It could also consider that there's a number of more or less
identical chips from other vendors that differ primarily in the supported display modes.

> I also have a couple of those TM1638 breakout boards with 8 digits, 8 single LEDs and 8 buttons that I might have a go with too. Have you given any thought to how the DT binding might support inputs as well? (The best time to be future-proof is before it's merged...)
> 
With regards to inputs at least I have no plans because I have no hw supporting input.
Since the first attempts to support this LED driver hw two years have been passed w/o any tangible (mainline) result.
Therefore I want to keep the initial version a MVP. Wanting to have too many features in an initial version
may result in longer discussions until maintainer or I give up.
Important is that user space interface / DT bindings are flexible enough so that future extensions don't have to break
existing users. And I think that's the case.

> Cheers,
> Robin.
> 

Heiner

>> v2:
>> - (re-)add Andreas' SoB to two patches
>> - fix YAML issues
>> - include ctype.h explicitly
>> - add info message in probe()
>>
>> v3:
>> - remove patch 1 because it has been applied via the SPI tree already
>> - fix remaining YAML issues in patch 2
>> - follow Miguel's suggestion on usage of Co-Developed-by
>>
>> v4:
>> - add patch for MAINTAINERS entry
>> - incorporate Miguel's review comments
>> - Replace Co-Developed-by with Co-developed-by (checkpatch)
>> v5:
>> - add vendor prefix to driver-specific dt properties
>>
>> Andreas Färber (1):
>>    dt-bindings: vendor-prefixes: Add Titan Micro Electronics
>>
>> Heiner Kallweit (5):
>>    dt-bindings: auxdisplay: Add Titan Micro Electronics TM1628
>>    docs: ABI: document tm1628 attribute display-text
>>    auxdisplay: add support for Titanmec TM1628 7 segment display
>>      controller
>>    arm64: dts: meson-gxl-s905w-tx3-mini: add support for the 7 segment
>>      display
>>    MAINTAINERS: Add entry for tm1628 auxdisplay driver
>>
>>   .../testing/sysfs-devices-auxdisplay-tm1628   |   7 +
>>   .../bindings/auxdisplay/titanmec,tm1628.yaml  |  92 +++++
>>   .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
>>   MAINTAINERS                                   |   7 +
>>   .../dts/amlogic/meson-gxl-s905w-tx3-mini.dts  |  59 +++
>>   drivers/auxdisplay/Kconfig                    |  11 +
>>   drivers/auxdisplay/Makefile                   |   1 +
>>   drivers/auxdisplay/tm1628.c                   | 376 ++++++++++++++++++
>>   8 files changed, 555 insertions(+)
>>   create mode 100644 Documentation/ABI/testing/sysfs-devices-auxdisplay-tm1628
>>   create mode 100644 Documentation/devicetree/bindings/auxdisplay/titanmec,tm1628.yaml
>>   create mode 100644 drivers/auxdisplay/tm1628.c
>>