Re: [PATCH v2 5/6] auxdisplay: add support for Titanmec TM1628 7 segment display controller

[Heiner Kallweit <hkallweit1@xxxxxxxxx>]

On 22.02.2022 09:19, Geert Uytterhoeven wrote:
> Hi Heiner,
> 
> On Mon, Feb 21, 2022 at 9:26 PM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
>> This patch 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.
>>
>> Tested-by: Christian Hewitt <christianshewitt@xxxxxxxxx>
>> Signed-off-by: Andreas Färber <afaerber@xxxxxxx>
>> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> 
> Thanks for your patch!
> 
>> --- /dev/null
>> +++ b/drivers/auxdisplay/tm1628.c
> 
>> +static int tm1628_show_text(struct tm1628 *s)
>> +{
>> +       static SEG7_CONVERSION_MAP(map_seg7, MAP_ASCII7SEG_ALPHANUM);
> 
> This mapping can not be overridden by the user.  Is there any
> specific reason you didn't make the mapping configurable from sysfs,
> cfr. map_seg7_{show,store}() in include/uapi/linux/map_to_7segment.h?
> 

The more features an initial driver version includes, the more discussion
topics pop up and make it less likely that we end up with at least something.
I think there's a reason why the driver was resting since the initial
attempt 2 yrs ago. Therefore I'd like to keep it as a MVP. 
If somebody should have the need for add-on features, then they can be
added later.

> Gr{oetje,eeting}s,
> 
>                         Geert
> 

Heiner

> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds