ledtrig-tty: add additional tty state evaluation

Changes in v4:
- Merging patch 3/4 into patch number 4/4 from previous series, because
  it fixes a problem that does not exist upstream. This was a note from
  the build robot regarding my change that I added with previous series.
  This change was never upstream and therefore this is not relevant.
- Update the commit message of patch 1/3 of this series, that this commit
  also changes the 'ndashes' to simple dashes. There were no changes, so
  I add the 'Reviewed-by' that the commit received before.
- With this patchset version I have reworked my implementation for the
  evaluation of the additional line state, so that this changes becomes
  smaller. As basis I have used the staged commits from Christian Marangi
  that makes this changes to the netdev trigger. This has already been
  applied to 'for-leds-next-next' by Lee Jones. I adapted this to the
  tty trigger.
  Convert device attr to macro:
  https://git.kernel.org/pub/scm/linux/kernel/git/lee/leds....
  Unify sysfs and state handling:
  https://git.kernel.org/pub/scm/linux/kernel/git/lee/leds....

Changes in v3:
- Add missing 'kernel test robot' information to the commit message.
- Additional information added to the commit message

Changes in v2:
- rename new function from tty_get_mget() to tty_get_tiocm() as
  requested by 'Jiri Slaby'.
- As suggested by 'Jiri Slaby', fixed tabs in function documentation
  throughout the file '/drivers/tty/tty_io.c' in a separate commit.
- Move the variable definition to the top in function
  'ledtrig_tty_work()'.
  This was reported by the 'kernel test robot' after my change in v1.
- Also set the 'max_brightness' to 'blink_brightness' if no
  'blink_brightness' was set. This fixes a problem at startup when the
  brightness is still set to 0 and only 'line_*' is evaluated. I looked
  in the netdev trigger and that's exactly how it's done there.

v1:
This is a follow-up patchset, based on the mailing list discussion from
March 2023 based on the old patchset v8 [1]. I have changed, the LED
trigger handling via the sysfs interfaces as suggested by Uwe Kleine-König.
[1] https://lore.kernel.org/linux-leds/20230306094113.273988-...

Florian Eckert (3):
  tty: whitespaces in descriptions corrected by replacing tabs with
    spaces
  tty: add new helper function tty_get_tiocm
  leds: ledtrig-tty: add new line mode evaluation

 .../ABI/testing/sysfs-class-led-trigger-tty   |  54 +++++
 drivers/leds/trigger/ledtrig-tty.c            | 192 +++++++++++++++++-
 drivers/tty/tty_io.c                          | 130 ++++++------
 include/linux/tty.h                           |   1 +
 4 files changed, 309 insertions(+), 68 deletions(-)

-- 
2.30.2