[PATCH v2 0/2] leds: ledtrig-tty: add tty_led_mode xtension

[PATCH v2 0/2] leds: ledtrig-tty: add tty_led_mode xtension

[Florian Eckert]

Hello,

here commes v2 of this series to add additional tty_led_modes.
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'

ledtrg-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 (2):
  tty: new helper function tty_get_mget
  trigger: ledtrig-tty: add additional modes

 .../ABI/testing/sysfs-class-led-trigger-tty   |  16 ++
 drivers/leds/trigger/ledtrig-tty.c            | 146 ++++++++++++++++--
 drivers/tty/tty_io.c                          |  30 +++-
 include/linux/tty.h                           |   1 +
 4 files changed, 171 insertions(+), 22 deletions(-)

-- 
2.30.2

[PATCH v2 1/2] 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 | 30 +++++++++++++++++++++++-------
 include/linux/tty.h  |  1 +
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 3149114bf130..f049ab8b3362 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2493,26 +2493,42 @@ 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
  * @p: pointer to result
  *
  * Obtain the modem status bits from the tty driver if the feature is
- * supported. Return -%ENOTTY if it is not available.
+ * supported.
  *
  * Locking: none (up to the driver)
  */
 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 v2 2/2] trigger: ledtrig-tty: add additional modes

[Florian Eckert]

Until now, the LED is flashed when data is transmitted. With a
legacy serial interface there are additional input signal lines.

CTS: Clear To Send       -> DCE is ready to accept data from the DTE
DSR: Data Set Ready      -> DCE is ready to receive and send data.
CAR: Data Carrier Detect -> DCE is receiving a carrier from a remote DCE.
RNG: Ring Indicator      -> DCE has detected an incoming ring on the line.

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>/tty_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   |  16 ++
 drivers/leds/trigger/ledtrig-tty.c            | 146 ++++++++++++++++--
 2 files changed, 147 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..31d62a5ae095 100644
--- a/Documentation/ABI/testing/sysfs-class-led-trigger-tty
+++ b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
@@ -4,3 +4,19 @@ 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 operating 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.
+		       LED on if line is high.
+		DSR:   DCE is ready to receive and send data.
+		       LED on if line is high.
+		CAR:   DCE is receiving a carrier from a remote DTE.
+		       LED on if line is high.
+		RNG:   DCE has detected an incoming ring signal.
+		       LED on if line is high.
diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
index f62db7e520b5..09d1be7b8ffb 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_CNT,
+	TTY_LED_CTS,
+	TTY_LED_DSR,
+	TTY_LED_CAR,
+	TTY_LED_RNG,
+	__TTY_LED_MAX
+};
+
 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_CNT] = "Tx/Rx", // Trasmit Data / 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 (RI)
 };
 
 static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
@@ -21,6 +39,71 @@ 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_MAX; i++) {
+		bool hit;
+
+		hit = tty_mode == i;
+		len += sysfs_emit_at(buf, len, "%s%s%s",
+				  hit ? "[" : "",
+				  mode[i],
+				  hit ? "]" : "");
+
+		if (i < __TTY_LED_MAX - 1)
+			len += sysfs_emit_at(buf, len, " ");
+	}
+
+	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;
+	enum tty_led_mode tty_mode = __TTY_LED_MAX;
+	int i;
+
+	/* Check for new line in string*/
+	if (size > 0 && buf[size - 1] == '\n')
+		size -= 1;
+
+	for (i = 0; i < __TTY_LED_MAX; i++) {
+		if (strncmp(buf, mode[i], size) == 0)
+			tty_mode = i;
+	}
+
+	if (tty_mode == __TTY_LED_MAX)
+		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 +159,18 @@ 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 +208,38 @@ 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_CNT:
+	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 +249,7 @@ 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 +262,9 @@ static int ledtrig_tty_activate(struct led_classdev *led_cdev)
 	if (!trigger_data)
 		return -ENOMEM;
 
+	/* set default mode */
+	trigger_data->mode = TTY_LED_CNT;
+
 	led_set_trigger_data(led_cdev, trigger_data);
 
 	INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
-- 
2.30.2

Re: [PATCH v2 1/2] tty: new helper function tty_get_mget

[Greg KH]

On Fri, Feb 17, 2023 at 10:44:02AM +0100, Florian Eckert wrote:
> 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 | 30 +++++++++++++++++++++++-------
>  include/linux/tty.h  |  1 +
>  2 files changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 3149114bf130..f049ab8b3362 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -2493,26 +2493,42 @@ 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.

Please make this proper kernel doc, the first comment line has to be /**

And you didn't mark -ENOTTY properly here either :(

> + */
> +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
>   * @p: pointer to result
>   *
>   * Obtain the modem status bits from the tty driver if the feature is
> - * supported. Return -%ENOTTY if it is not available.
> + * supported.

Why did you remove the return value statement from the documentation
here?  It's still true, right?

thanks,

greg k-h