On Thu, May 03, 2018 at 12:10:47PM +0200, Pavel Machek wrote:

Hi!

quoted

The trigger fires when data is pushed to the ldisc. This is a bit later
than the actual receiving of data but has the nice benefit that it
doesn't need adaption for each driver and isn't in the hot path.

Signed-off-by: Uwe Kleine-K?nig <redacted>

Well, why not, but there certainly should be config option? Because I
really don't see many people wanting to use this trigger.

Yeah, can be done. I'll implement this for v2.

quoted

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index c996b6859c5e..4d364b77b1a7 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c

@@ -17,6 +17,7 @@
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/ratelimit.h>
+#include <linux/leds.h>
 
 
 #define MIN_TTYB_SIZE	256

@@ -499,6 +500,7 @@ static void flush_to_ldisc(struct work_struct *work)
 		struct tty_buffer *head = buf->head;
 		struct tty_buffer *next;
 		int count;
+		unsigned long delay = 50 /* ms */;
 
 		/* Ldisc or user is trying to gain exclusive access */
 		if (atomic_read(&buf->priority))

@@ -521,6 +523,8 @@ static void flush_to_ldisc(struct work_struct *work)
 			continue;
 		}
 
+		led_trigger_blink_oneshot(port->led_trigger_rx, &delay, &delay, 0);
+
 		count = receive_buf(port, head, count);
 		if (!count)
 			break;

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 25d736880013..51b78a585417 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c

@@ -16,6 +16,7 @@
 #include <linux/wait.h>
 #include <linux/bitops.h>
 #include <linux/delay.h>
+#include <linux/leds.h>
 #include <linux/module.h>
 #include <linux/serdev.h>
 

@@ -157,6 +158,18 @@ struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
 
 	tty_port_link_device(port, driver, index);
 
+	port->led_trigger_rx_name = kasprintf(GFP_KERNEL, "%s%d-rx",
+					      driver->name, index);
+	if (!port->led_trigger_rx_name) {
+		pr_err("Failed to allocate trigger name for %s%d\n",
+		       driver->name, index);
+		goto skip_trigger;
+	}
+
+	led_trigger_register_simple(port->led_trigger_rx_name,
+				    &port->led_trigger_rx);
+
+skip_trigger:
 	dev = serdev_tty_port_register(port, device, driver, index);
 	if (PTR_ERR(dev) != -ENODEV) {
 		/* Skip creating cdev if we registered a serdev device */

@@ -206,6 +219,9 @@ void tty_port_unregister_device(struct tty_port *port,
 	if (ret == 0)
 		return;
 
+	led_trigger_unregister_simple(port->led_trigger_rx);

Is it ok to unregister if it was not registered in the first place?

led_trigger_unregister_simple() looks as follows:

	if (trig)
		led_trigger_unregister(trig);
	kfree(trig);

So yes, it does the right thing when it wasn't registered. Assuming it
is NULL then, which doesn't seem to be guaranteed. Probably I'd need

	port->led_trigger_rx = NULL
	
if kasprintf failed.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |