Re: [PATCH v2] tty: implement led triggers

Johan Hovold
2018-05-07T08:02:52Z

On Thu, May 03, 2018 at 10:19:52PM +0200, Uwe Kleine-König wrote:
> The rx 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.
>
> Similarily the tx trigger fires when data taken from the ldisc.

You meant copied from user space, or written to the ldisc, here.

Note that the rx-path is shared with serdev, but the write path is not.
So with this series, serdev devices would only trigger the rx-led.

> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
> Changes since v1, sent with Message-Id:
> 20180503100448.1350-1-u.kleine-koenig@pengutronix.de:
>
> - implement tx trigger;
> - introduce Kconfig symbol for conditional compilation;
> - set trigger to NULL if allocating the name failed to not free random
> pointers in case the port struct wasn't zeroed;
> - use if/else instead of goto

> @@ -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 */;

Comment after the semicolon?

>
> /* Ldisc or user is trying to gain exclusive access */
> if (atomic_read(&buf->priority))

> diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
> index 25d736880013..f042879a597c 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 +158,30 @@ struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
>
> tty_port_link_device(port, driver, index);
>
> +#ifdef CONFIG_TTY_LEDS_TRIGGER
> + port->led_trigger_rx_name = kasprintf(GFP_KERNEL, "%s%d-rx",
> + driver->name, index);
> + if (port->led_trigger_rx_name) {
> + led_trigger_register_simple(port->led_trigger_rx_name,
> + &port->led_trigger_rx);
> + } else {
> + port->led_trigger_rx = NULL;
> + pr_err("Failed to allocate trigger name for %s%d\n",
> + driver->name, index);
> + }
> +
> + port->led_trigger_tx_name = kasprintf(GFP_KERNEL, "%s%d-tx",
> + driver->name, index);
> + if (port->led_trigger_tx_name) {
> + led_trigger_register_simple(port->led_trigger_tx_name,
> + &port->led_trigger_tx);
> + } else {
> + port->led_trigger_tx = NULL;
> + pr_err("Failed to allocate trigger name for %s%d\n",
> + driver->name, index);
> + }
> +#endif

Besides the ugly ifdefs here, you're leaking the above LED resources in
the error paths below (e.g. on probe deferrals).

> dev = serdev_tty_port_register(port, device, driver, index);
> if (PTR_ERR(dev) != -ENODEV) {
> /* Skip creating cdev if we registered a serdev device */

> @@ -249,6 +249,13 @@ struct tty_port {
> set to size of fifo */
> struct kref kref; /* Ref counter */
> void *client_data;
> +
> +#ifdef CONFIG_TTY_LEDS_TRIGGER
> + struct led_trigger *led_trigger_rx;
> + char *led_trigger_rx_name;

const?

> + struct led_trigger *led_trigger_tx;
> + char *led_trigger_tx_name;

ditto.

> +#endif

Johan