[PATCH v8 0/3] leds: ledtrig-tty: add tty_led_mode xtension

[PATCH v8 0/3] leds: ledtrig-tty: add tty_led_mode xtension

[Florian Eckert]

Hello,

here commes v8 of this series to add additional tty_led_modes.

v8:
Changes compared to the v7 patchset with
20230222083335.847655-1-fe@dev.tdt.de are.

* Update 'Documentation/ABI/testing/sysfs-class-led-trigger-tty'
  with the suggested changes.
* Use a meaningfull name for the Rx/Tx enum.
* Do not use C++ comments style

Add a new patch 'ledtrig-tty-fix-brightness-set' to fix an issue with
LEDs that are connected via GPIOs to the SOC with the device driver
'leds-gpio'. In my view, the wrong function is being used here. LEDs
that do not need and do not have a delayed call do not work with the
current implementation. Therefore, the 'led_set_brightness_nosleep'
function must be used.


v7:
Changes compared to the v5 patchset with
20230222075539.484878-1-fe@dev.tdt.de are.

Addressed review comments by Jiri Slaby are:

Thanks for the hint with the command 'make htmldocs SPHINXDIRS="admin-guide"'.
Unfortunately, I did not know that. I have now verified it also in the
browser. In my opinion, the list is now also displayed correctly in
the documentation.


v6:
Changes compared to the v5 patchset with
20230221081901.15557-1-fe@dev.tdt.de are.

Addressed review comments by kernel test robot are:

* fix Documentation/ABI/testing/sysfs-class-led-trigger-tty:9:
  WARNING: Unexpected indentation.
* fix Documentation/ABI/testing/sysfs-class-led-trigger-tty:9:
  WARNING: Block quote ends without a blank line; unexpected unindent.

Thanks to Jiri Slaby, who gave me the crucial hint of what I need to fix,
to possibly make the 'Kernel test robot' happy.


v5:
Changes compared to the v4 patchset with
20230220152038.3877596-1-fe@dev.tdt.de are.

Sorry for the inconvenience, but I sent the wrong patch for
ledtrig-tty.c in v4. The v5 patchset now includes all the changes I
specified in the v4 patchset.


v4:
Changes compared to the v3 patchset with
20230220093739.320478-1-fe@dev.tdt.de are.

Addressed review comments by Jiri Slaby are:

ledtrig-tty.c:
- Do not use __TTY_LED_MAX pattern us instead __TTY_LED_LAST = TTY_LED_RNG
- Move declartion and assignment into one singel line
- Use __TTY_LED_LAST pattern, to simplify tty_mode_show and
  tty_mode_store handling


v3:
Changes compared to the v2 patchset with
20230217094403.1574468-1-fe@dev.tdt.de are.

Addressed review comments by Greg K-H are:

tty.h:
- Fix first comment line and remark -%ENOTTY for the new function
  'tty_get_mget' to make a proper kernel doc.
- Add the return value -%ENOTTY again, I thought it was no longer needed.


v2:
Changes compared to the initial patchset with
20230213140638.620206-1-fe@dev.tdt.de are.

Addressed review comments by Jiri Slaby are:

tty.h:
- Fix compilation error because of wrong rebaseing
- Remove empty lines
- Use new 'tty_get_mget' in 'tty_tiocmget'

ledtrig-tty.c:
- Update commit description
- Use enum for tty_led_mod in struct ledtrig_tty_date
- Rename sysfs file from 'mode' to 'tty_led_mode'
- Change tty_led_mode show function to use loop instead of switch/case
- Change tty_led_mode store function to use loop instead of switch/case
- Check return value of function tty_get_mget

Florian Eckert (3):
  tty: new helper function tty_get_mget
  trigger: ledtrig-tty: add additional modes
  ledtrig-tty: call correct brightness set function

 .../ABI/testing/sysfs-class-led-trigger-tty   |  18 +++
 drivers/leds/trigger/ledtrig-tty.c            | 145 ++++++++++++++++--
 drivers/tty/tty_io.c                          |  28 +++-
 include/linux/tty.h                           |   1 +
 4 files changed, 171 insertions(+), 21 deletions(-)

-- 
2.30.2

[PATCH v8 1/3] tty: new helper function tty_get_mget

[Florian Eckert]

For a given struct tty_struct, this provides the appropriate tty line
state flags needed to add more modes to the ledtrig-tty trigger.

The new function is then used to get via tty_tiocmget() the different tty
line states.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
---
 drivers/tty/tty_io.c | 28 ++++++++++++++++++++++------
 include/linux/tty.h  |  1 +
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 3149114bf130..a068b03a0828 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2493,6 +2493,24 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
 	return retval;
 }
 
+/**
+ * tty_get_mget		-	get modem status
+ * @tty: tty device
+ *
+ * Obtain the modem status bits from the tty driver if the feature
+ * is supported. Return -%ENOTTY if it is not available.
+ */
+int tty_get_mget(struct tty_struct *tty)
+{
+	int retval = -ENOTTY;
+
+	if (tty->ops->tiocmget)
+		retval = tty->ops->tiocmget(tty);
+
+	return retval;
+}
+EXPORT_SYMBOL_GPL(tty_get_mget);
+
 /**
  * tty_tiocmget		-	get modem status
  * @tty: tty device
@@ -2505,14 +2523,12 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
  */
 static int tty_tiocmget(struct tty_struct *tty, int __user *p)
 {
-	int retval = -ENOTTY;
+	int retval;
 
-	if (tty->ops->tiocmget) {
-		retval = tty->ops->tiocmget(tty);
+	retval = tty_get_mget(tty);
+	if (retval >= 0)
+		retval = put_user(retval, p);
 
-		if (retval >= 0)
-			retval = put_user(retval, p);
-	}
 	return retval;
 }
 
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 730c3301d710..825186c0fec1 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -421,6 +421,7 @@ int tty_unthrottle_safe(struct tty_struct *tty);
 int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
 int tty_get_icount(struct tty_struct *tty,
 		struct serial_icounter_struct *icount);
+int tty_get_mget(struct tty_struct *tty);
 int is_current_pgrp_orphaned(void);
 void tty_hangup(struct tty_struct *tty);
 void tty_vhangup(struct tty_struct *tty);
-- 
2.30.2

[PATCH v8 2/3] trigger: ledtrig-tty: add additional modes

[Florian Eckert]

Add additional modes to trigger the selected LED.
The following modes are supported:

Tx/Rx:	Flash LED on data transmission (default)
CTS:	DCE Ready to accept data from the DTE.
DSR:	DCE is ready to receive and send data.
CAR:	DCE is receiving a carrier from a remote DTE.
RNG:	DCE has detected an incoming ring signal.

The mode can be changed for example with the following command:
echo "CTS" > /sys/class/leds/<led>/mode

This would turn on the LED, when the DTE(modem) signals the DCE that it
is ready to accept data.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
---
 .../ABI/testing/sysfs-class-led-trigger-tty   |  18 +++
 drivers/leds/trigger/ledtrig-tty.c            | 143 ++++++++++++++++--
 2 files changed, 146 insertions(+), 15 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-tty b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
index 2bf6b24e781b..2e4e4c009a21 100644
--- a/Documentation/ABI/testing/sysfs-class-led-trigger-tty
+++ b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
@@ -4,3 +4,21 @@ KernelVersion:	5.10
 Contact:	linux-leds@vger.kernel.org
 Description:
 		Specifies the tty device name of the triggering tty
+
+What:		/sys/class/leds/<led>/mode
+Date:		January 2023
+KernelVersion:	6.3
+Description:
+		Specifies the mode to trigger the LED.
+		The following operating modes are supported:
+
+		=====  ============================================
+		Tx/Rx  Flash LED on data transmission (default)
+		CTS    DCE Ready to accept data from the DTE
+		DSR    DCE is ready to receive and send data
+		CAR    DCE is receiving a carrier from a remote DTE
+		RNG    DCE has detected an incoming ring signal
+		=====  ============================================
+
+		In CTS/DSR/CAR/RNG modes, the LED is enabled when the
+		tty line is high.
\ No newline at end of file
diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
index f62db7e520b5..d3407830fa69 100644
--- a/drivers/leds/trigger/ledtrig-tty.c
+++ b/drivers/leds/trigger/ledtrig-tty.c
@@ -7,6 +7,15 @@
 #include <linux/tty.h>
 #include <uapi/linux/serial.h>
 
+enum tty_led_mode {
+	TTY_LED_RXTX,
+	TTY_LED_CTS,
+	TTY_LED_DSR,
+	TTY_LED_CAR,
+	TTY_LED_RNG,
+	_TTY_LED_LAST = TTY_LED_RNG
+};
+
 struct ledtrig_tty_data {
 	struct led_classdev *led_cdev;
 	struct delayed_work dwork;
@@ -14,6 +23,15 @@ struct ledtrig_tty_data {
 	const char *ttyname;
 	struct tty_struct *tty;
 	int rx, tx;
+	enum tty_led_mode mode;
+};
+
+static const char * const mode[] = {
+	[TTY_LED_RXTX] = "Tx/Rx", /* Transmit and Receive data */
+	[TTY_LED_CTS] = "CTS", /* CTS clear to send */
+	[TTY_LED_DSR] = "DSR", /* DSR data set ready */
+	[TTY_LED_CAR] = "CAR", /* CAR data carrier detect (DCD) */
+	[TTY_LED_RNG] = "RNG", /* RNG ring indicator */
 };
 
 static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
@@ -21,6 +39,70 @@ static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
 	schedule_delayed_work(&trigger_data->dwork, 0);
 }
 
+static ssize_t ledtrig_tty_mode_show(char *buf, enum tty_led_mode tty_mode)
+{
+	int len = 0;
+	int i;
+
+	for (i = 0; i <= _TTY_LED_LAST; i++) {
+		bool hit = tty_mode == i;
+		bool last = i == _TTY_LED_LAST;
+
+		len += sysfs_emit_at(buf, len, "%s%s%s%s",
+				  hit ? "[" : "",
+				  mode[i],
+				  hit ? "]" : "",
+				  last ? "" : " ");
+	}
+
+	len += sysfs_emit_at(buf, len, "\n");
+
+	return len;
+}
+
+static ssize_t tty_led_mode_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	enum tty_led_mode tty_mode;
+
+	mutex_lock(&trigger_data->mutex);
+	tty_mode = trigger_data->mode;
+	mutex_unlock(&trigger_data->mutex);
+
+	return ledtrig_tty_mode_show(buf, tty_mode);
+}
+
+static ssize_t tty_led_mode_store(struct device *dev,
+				  struct device_attribute *attr, const char *buf,
+				  size_t size)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	ssize_t ret = size;
+	int i;
+	enum tty_led_mode tty_mode = _TTY_LED_LAST;
+
+	/* Check for new line in string */
+	if (size > 0 && buf[size - 1] == '\n')
+		size -= 1;
+
+	for (i = 0; i <= _TTY_LED_LAST; i++)
+		if (strncmp(buf, mode[i], size) == 0) {
+			tty_mode = i;
+			break;
+		}
+
+	if (i > _TTY_LED_LAST)
+		return -EINVAL;
+
+	mutex_lock(&trigger_data->mutex);
+	trigger_data->mode = tty_mode;
+	mutex_unlock(&trigger_data->mutex);
+
+	return ret;
+}
+static DEVICE_ATTR_RW(tty_led_mode);
+
 static ssize_t ttyname_show(struct device *dev,
 			    struct device_attribute *attr, char *buf)
 {
@@ -76,6 +158,17 @@ static ssize_t ttyname_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(ttyname);
 
+static void ledtrig_tty_flags(struct ledtrig_tty_data *trigger_data, unsigned int flag)
+{
+	unsigned int status;
+
+	status = tty_get_mget(trigger_data->tty);
+	if (status & flag)
+		led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
+	else
+		led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+}
+
 static void ledtrig_tty_work(struct work_struct *work)
 {
 	struct ledtrig_tty_data *trigger_data =
@@ -113,21 +206,37 @@ static void ledtrig_tty_work(struct work_struct *work)
 		trigger_data->tty = tty;
 	}
 
-	ret = tty_get_icount(trigger_data->tty, &icount);
-	if (ret) {
-		dev_info(trigger_data->tty->dev, "Failed to get icount, stopped polling\n");
-		mutex_unlock(&trigger_data->mutex);
-		return;
-	}
-
-	if (icount.rx != trigger_data->rx ||
-	    icount.tx != trigger_data->tx) {
-		led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
-
-		trigger_data->rx = icount.rx;
-		trigger_data->tx = icount.tx;
-	} else {
-		led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+	switch (trigger_data->mode) {
+	case TTY_LED_CTS:
+		ledtrig_tty_flags(trigger_data, TIOCM_CTS);
+		break;
+	case TTY_LED_DSR:
+		ledtrig_tty_flags(trigger_data, TIOCM_DSR);
+		break;
+	case TTY_LED_CAR:
+		ledtrig_tty_flags(trigger_data, TIOCM_CAR);
+		break;
+	case TTY_LED_RNG:
+		ledtrig_tty_flags(trigger_data, TIOCM_RNG);
+		break;
+	case TTY_LED_RXTX:
+	default:
+		ret = tty_get_icount(trigger_data->tty, &icount);
+		if (ret) {
+			dev_info(trigger_data->tty->dev, "Failed to get icount, stopped polling\n");
+			mutex_unlock(&trigger_data->mutex);
+			return;
+		}
+
+		if (icount.rx != trigger_data->rx || icount.tx != trigger_data->tx) {
+			led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
+
+			trigger_data->rx = icount.rx;
+			trigger_data->tx = icount.tx;
+		} else {
+			led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+		}
+		break;
 	}
 
 out:
@@ -137,6 +246,7 @@ static void ledtrig_tty_work(struct work_struct *work)
 
 static struct attribute *ledtrig_tty_attrs[] = {
 	&dev_attr_ttyname.attr,
+	&dev_attr_tty_led_mode.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(ledtrig_tty);
@@ -149,6 +259,9 @@ static int ledtrig_tty_activate(struct led_classdev *led_cdev)
 	if (!trigger_data)
 		return -ENOMEM;
 
+	/* Set default mode */
+	trigger_data->mode = TTY_LED_RXTX;
+
 	led_set_trigger_data(led_cdev, trigger_data);
 
 	INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
-- 
2.30.2

[PATCH v8 3/3] ledtrig-tty: call correct brightness set function

[Florian Eckert]

The problem is, however, that with LEDs that are connected directly to
the SOC via a GPIO, the LED cannot be switched on or off.
Because the 'leds-gpio' device driver does not need a delayed work.

If we look at the callstack for the function 'led_set_brightness_sync',
then at the end it is checked whether the LED device driver has the
function 'brightness_set_blocking' implemented. This is not the case for
the 'leds-gpio' device.

The function 'brightness_set_blocking' returns LED devices -ENOTSUPP.
This is not evaluated in 'ledtrig-tty' trigger.

In order for the trigger to also work with LED that does not have the
'brightness_set_blocking' function implemented, we must therefore use the
internal API of the LED subsystem and use the function
'led_set_brightness_nosleep'.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
---
 drivers/leds/trigger/ledtrig-tty.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
index d3407830fa69..132e809898a7 100644
--- a/drivers/leds/trigger/ledtrig-tty.c
+++ b/drivers/leds/trigger/ledtrig-tty.c
@@ -7,6 +7,8 @@
 #include <linux/tty.h>
 #include <uapi/linux/serial.h>
 
+#include "../leds.h"
+
 enum tty_led_mode {
 	TTY_LED_RXTX,
 	TTY_LED_CTS,
@@ -164,9 +166,9 @@ static void ledtrig_tty_flags(struct ledtrig_tty_data *trigger_data, unsigned in
 
 	status = tty_get_mget(trigger_data->tty);
 	if (status & flag)
-		led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
+		led_set_brightness_nosleep(trigger_data->led_cdev, LED_ON);
 	else
-		led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+		led_set_brightness_nosleep(trigger_data->led_cdev, LED_OFF);
 }
 
 static void ledtrig_tty_work(struct work_struct *work)
@@ -229,12 +231,12 @@ static void ledtrig_tty_work(struct work_struct *work)
 		}
 
 		if (icount.rx != trigger_data->rx || icount.tx != trigger_data->tx) {
-			led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
+			led_set_brightness_nosleep(trigger_data->led_cdev, LED_ON);
 
 			trigger_data->rx = icount.rx;
 			trigger_data->tx = icount.tx;
 		} else {
-			led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+			led_set_brightness_nosleep(trigger_data->led_cdev, LED_OFF);
 		}
 		break;
 	}
-- 
2.30.2

Re: [PATCH v8 0/3] leds: ledtrig-tty: add tty_led_mode xtension

[Jiri Slaby]

On 06. 03. 23, 10:41, Florian Eckert wrote:
> Hello,
> 
> here commes v8 of this series to add additional tty_led_modes.

I think u r 2 fast. Uwe had some more comments on v7.

Don't be afraid to wait some days after the last comments ;). As it is, 
it makes the review harder...

> v8:
> Changes compared to the v7 patchset with
> 20230222083335.847655-1-fe@dev.tdt.de are.
> 
> * Update 'Documentation/ABI/testing/sysfs-class-led-trigger-tty'
>    with the suggested changes.
> * Use a meaningfull name for the Rx/Tx enum.
> * Do not use C++ comments style
> 
> Add a new patch 'ledtrig-tty-fix-brightness-set' to fix an issue with
> LEDs that are connected via GPIOs to the SOC with the device driver
> 'leds-gpio'. In my view, the wrong function is being used here. LEDs
> that do not need and do not have a delayed call do not work with the
> current implementation. Therefore, the 'led_set_brightness_nosleep'
> function must be used.
> 
> 
> v7:
> Changes compared to the v5 patchset with
> 20230222075539.484878-1-fe@dev.tdt.de are.
> 
> Addressed review comments by Jiri Slaby are:
> 
> Thanks for the hint with the command 'make htmldocs SPHINXDIRS="admin-guide"'.
> Unfortunately, I did not know that. I have now verified it also in the
> browser. In my opinion, the list is now also displayed correctly in
> the documentation.
> 
> 
> v6:
> Changes compared to the v5 patchset with
> 20230221081901.15557-1-fe@dev.tdt.de are.
> 
> Addressed review comments by kernel test robot are:
> 
> * fix Documentation/ABI/testing/sysfs-class-led-trigger-tty:9:
>    WARNING: Unexpected indentation.
> * fix Documentation/ABI/testing/sysfs-class-led-trigger-tty:9:
>    WARNING: Block quote ends without a blank line; unexpected unindent.
> 
> Thanks to Jiri Slaby, who gave me the crucial hint of what I need to fix,
> to possibly make the 'Kernel test robot' happy.
> 
> 
> v5:
> Changes compared to the v4 patchset with
> 20230220152038.3877596-1-fe@dev.tdt.de are.
> 
> Sorry for the inconvenience, but I sent the wrong patch for
> ledtrig-tty.c in v4. The v5 patchset now includes all the changes I
> specified in the v4 patchset.
> 
> 
> v4:
> Changes compared to the v3 patchset with
> 20230220093739.320478-1-fe@dev.tdt.de are.
> 
> Addressed review comments by Jiri Slaby are:
> 
> ledtrig-tty.c:
> - Do not use __TTY_LED_MAX pattern us instead __TTY_LED_LAST = TTY_LED_RNG
> - Move declartion and assignment into one singel line
> - Use __TTY_LED_LAST pattern, to simplify tty_mode_show and
>    tty_mode_store handling
> 
> 
> v3:
> Changes compared to the v2 patchset with
> 20230217094403.1574468-1-fe@dev.tdt.de are.
> 
> Addressed review comments by Greg K-H are:
> 
> tty.h:
> - Fix first comment line and remark -%ENOTTY for the new function
>    'tty_get_mget' to make a proper kernel doc.
> - Add the return value -%ENOTTY again, I thought it was no longer needed.
> 
> 
> v2:
> Changes compared to the initial patchset with
> 20230213140638.620206-1-fe@dev.tdt.de are.
> 
> Addressed review comments by Jiri Slaby are:
> 
> tty.h:
> - Fix compilation error because of wrong rebaseing
> - Remove empty lines
> - Use new 'tty_get_mget' in 'tty_tiocmget'
> 
> ledtrig-tty.c:
> - Update commit description
> - Use enum for tty_led_mod in struct ledtrig_tty_date
> - Rename sysfs file from 'mode' to 'tty_led_mode'
> - Change tty_led_mode show function to use loop instead of switch/case
> - Change tty_led_mode store function to use loop instead of switch/case
> - Check return value of function tty_get_mget
> 
> Florian Eckert (3):
>    tty: new helper function tty_get_mget
>    trigger: ledtrig-tty: add additional modes
>    ledtrig-tty: call correct brightness set function
> 
>   .../ABI/testing/sysfs-class-led-trigger-tty   |  18 +++
>   drivers/leds/trigger/ledtrig-tty.c            | 145 ++++++++++++++++--
>   drivers/tty/tty_io.c                          |  28 +++-
>   include/linux/tty.h                           |   1 +
>   4 files changed, 171 insertions(+), 21 deletions(-)
> 

-- 
js
suse labs

Re: [PATCH v8 0/3] leds: ledtrig-tty: add tty_led_mode xtension

[Florian Eckert]

>> 
>> here commes v8 of this series to add additional tty_led_modes.
> 
> I think u r 2 fast. Uwe had some more comments on v7.
> 
> Don't be afraid to wait some days after the last comments ;). As it
> is, it makes the review harder...
> 

That was probably a race condition ;-) This must have been received when 
I sent the v8.