leds: ledtrig-tty: Add additional line state evaluation

The serial tty interface also supports additional input signals, that
can also be evaluated within this trigger. This change is adding the
following additional input sources, which could be controlled
via the '/sys/class/<leds>/' sysfs interface.

Explanation:
DCE = Data Communication Equipment (Modem)
DTE = Data Terminal Equipment (Computer)

- cts:
DCE is ready to accept data from the DTE (CTS = Clear To Send). If
the line state is detected, the LED is switched on.
If set to 0 (default), the LED will not evaluate CTS.
If set to 1, the LED will evaluate CTS.

- dsr:
DCE is ready to receive and send data (DSR = Data Set Ready). If the
line state is detected, the LED is switched on.
If set to 0 (default), the LED will not evaluate DSR.
If set to 1, the LED will evaluate DSR.

- dcd:
DTE is receiving a carrier from the DCE (DCD = Data Carrier Detect).
If the line state is detected, the LED is switched on.
If set to 0 (default), the LED will not evaluate DCD.
If set to 1, the LED will evaluate DCD.

- rng:
DCE has detected an incoming ring signal on the telephone line
(RNG = Ring Indicator). If the line state is detected, the LED is
switched on.
If set to 0 (default), the LED will not evaluate RNG.
If set to 1, the LED will evaluate RNG.

Also add an invert flag on LED blink, so that the LED blinks in the
correct order.

* If one off the new enabled input signals are evaluatet as 'enabled',
and data are transmitted, then the LED should first blink 'off' and
then 'on' (invert).
* If all the new enabled input signals are evaluatet as 'disabled',
and data are transmitted, then the LED should first blink 'on' and
then 'off'.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
Reviewed-by: Maarten Brock <m.brock@vanmierlo.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20231127110311.3583957-5-fe@dev.tdt.de
Signed-off-by: Lee Jones <lee@kernel.org>

leds: ledtrig-tty: Make rx tx activitate configurable

Until now, the LED blinks when data is sent via the tty (rx/tx).
This is not configurable.

This change adds the possibility to make the indication for the direction
of the transmitted data independently controllable via the new rx and
tx sysfs entries.

- rx:
Signal reception (rx) of data on the named tty device.
If set to 0, the LED will not blink on reception.
If set to 1 (default), the LED will blink on reception.

- tx:
Signal transmission (tx) of data on the named tty device.
If set to 0, the LED will not blink on transmission.
If set to 1 (default), the LED will blink on transmission.

This new sysfs entry are on by default. Thus the trigger behaves as
before this change.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20231127110311.3583957-4-fe@dev.tdt.de
Signed-off-by: Lee Jones <lee@kernel.org>

leds: ledtrig-tty: Replace mutex with completion

With this commit, the mutex handling is replaced by the completion
handling. When handling mutex, it must always be ensured that the held
mutex is also released again. This is more error-prone should the number
of code paths increase.

This is a preparatory commit to make the trigger more configurable via
additional sysfs parameters. With this change, the worker always runs and
is no longer stopped if no ttyname is set.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20231127110311.3583957-3-fe@dev.tdt.de
Signed-off-by: Lee Jones <lee@kernel.org>

leds: ledtrig-tty: Free allocated ttyname buffer on deactivate

The ttyname buffer for the ledtrig_tty_data struct is allocated in the
sysfs ttyname_store() function. This buffer must be released on trigger
deactivation. This was missing and is thus a memory leak.

While we are at it, the TTY handler in the ledtrig_tty_data struct should
also be returned in case of the trigger deactivation call.

Cc: stable@vger.kernel.org
Fixes: fd4a641ac88f ("leds: trigger: implement a tty trigger")
Signed-off-by: Florian Eckert <fe@dev.tdt.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20231127081621.774866-1-fe@dev.tdt.de
Signed-off-by: Lee Jones <lee@kernel.org>

leds: trigger: tty: Do not use LED_ON/OFF constants, use led_blink_set_oneshot instead

The tty LED trigger uses the obsolete LED_ON & LED_OFF constants when
setting LED brightness. This is bad because the LED_ON constant is equal
to 1, and so when activating the tty LED trigger on a LED class device
with max_brightness greater than 1, the LED is dimmer than it can be
(when max_brightness is 255, the LED is very dimm indeed; some devices
translate 1/255 to 0, so the LED is OFF all the time).

Instead of directly setting brightness to a specific value, use the
led_blink_set_oneshot() function from LED core to configure the blink.
This function takes the current configured brightness as blink
brightness if not zero, and max brightness otherwise.

This also changes the behavior of the TTY LED trigger. Previously if
rx/tx stats kept changing, the LED was ON all the time they kept
changing. With this patch the LED will blink on TTY activity.

Fixes: fd4a641ac88f ("leds: trigger: implement a tty trigger")
Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20230802090753.13611-1-kabel@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>

leds: trigger/tty: Use led_set_brightness_sync() from workqueue

led_set_brightness() involves scheduling a workqueue. As here the led's
brightness setting is done in context of the trigger's workqueue this is
unjustified overhead and it's more sensible to use
led_set_brightness_sync().

Fixes: fd4a641ac88f ("leds: trigger: implement a tty trigger")
Reported-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20210219133307.4840-3-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

leds: trigger: Fix error path to not unlock the unlocked mutex

ttyname is allocated before the mutex is taken, so it must not be
unlocked in the error path.

Fixes: fd4a641ac88f ("leds: trigger: implement a tty trigger")
Reported-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20210219133307.4840-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

leds: trigger: implement a tty trigger

Usage is as follows:

myled=ledname
tty=ttyS0

echo tty > /sys/class/leds/$myled/trigger
echo $tty > /sys/class/leds/$myled/ttyname

. When this new trigger is active it periodically checks the tty's
statistics and when it changed since the last check the led is flashed
once.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20210113173018.bq2fkea2o3yp6rf6@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>