Improved text display abilities

[Lurker00]

Tested on H96 MAX X3 with FD6551, but should work with any supported controller, because high level API is used.

1. Adds an ability to display

• "boot" on start, until the service starts displaying time;
• "----" when the driver is closed by the service;
• "stop" on the driver remove;
• "shut" on system shutdown.

Parameters vfd_show_boot and vfd_show_stop make those features optional. Default values are 1 (display).

2. Attribute "text" allows to display any supported text, e.g.

echo "text" > /sys/class/leds/openvfd/text

Of course, if the service is running, it will change the display back to time in a second.

3. Support for using indicators without the service.

Writing to /sys/class/leds/openvfd/led_on and /sys/class/leds/openvfd/led_off only changes internal bit mask. Full display update is required for indicators to change. The driver keeps the last data sent to the display and re-sends it when an indicator needs to be updated.

4. Logging improved and extended.

[hbiyik]

thats a great PR, tested and can verify all works as expected on my FD650.

i have a suggestion to make module parameters, shut, boot, stop as charp so that it can be configured for branding or multilingual purposes.

if the parameter is not set or empty value, then nothing to be shows.

[Lurker00]

i have a suggestion to make module parameters, shut, boot, stop as charp

I don't believe it worth additional efforts for both development and further deployment:

• The number of available characters is very limited.
• Such type of the parameters require explicit set their values for every use. The current state is "drop-in" solution.

Also take into account that these words are used only during short periods of a device life cycle. In between, any text can be displayed via text attribute.