linux-kernel - Re: [PATCH 2/2] leds: trigger: ledtrig-tty: add additional modes

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Date:   Tue, 14 Feb 2023 08:54:06 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Florian Eckert <fe@....tdt.de>, u.kleine-koenig@...gutronix.de,
        gregkh@...uxfoundation.org, pavel@....cz, lee@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        Eckert.Florian@...glemail.com
Subject: Re: [PATCH 2/2] leds: trigger: ledtrig-tty: add additional modes

On 13. 02. 23, 15:06, Florian Eckert wrote:
> Add additional modes to trigger the selected LED.
> The following modes are supported:
> 
> TD/RD:	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 will emit only:
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@....tdt.de>
...
> --- a/drivers/leds/trigger/ledtrig-tty.c
> +++ b/drivers/leds/trigger/ledtrig-tty.c
> @@ -7,6 +7,14 @@
>   #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,
> +};
> +
>   struct ledtrig_tty_data {
>   	struct led_classdev *led_cdev;
>   	struct delayed_work dwork;
> @@ -14,6 +22,15 @@ struct ledtrig_tty_data {
>   	const char *ttyname;
>   	struct tty_struct *tty;
>   	int rx, tx;
> +	unsigned int mode;

Why not the enum then?

> +};
> +
> +static const char * const mode[] = {

This is not a wise name.

> +	[TTY_LED_CNT] = "TD/RD", // 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 +38,74 @@ static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
>   	schedule_delayed_work(&trigger_data->dwork, 0);
>   }
>   
> +static ssize_t 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);
> +
> +	switch (tty_mode) {
> +	case TTY_LED_CTS:
> +		return sprintf(buf, "%s [%s] %s %s %s\n", mode[TTY_LED_CNT],
> +				mode[TTY_LED_CTS], mode[TTY_LED_DSR],
> +				mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
> +	case TTY_LED_DSR:
> +		return sprintf(buf, "%s %s [%s] %s %s\n", mode[TTY_LED_CNT],
> +				mode[TTY_LED_CTS], mode[TTY_LED_DSR],
> +				mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
> +	case TTY_LED_CAR:
> +		return sprintf(buf, "%s %s %s [%s] %s\n", mode[TTY_LED_CNT],
> +				mode[TTY_LED_CTS], mode[TTY_LED_DSR],
> +				mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
> +	case TTY_LED_RNG:
> +		return sprintf(buf, "%s %s %s %s [%s]\n", mode[TTY_LED_CNT],
> +				mode[TTY_LED_CTS], mode[TTY_LED_DSR],
> +				mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
> +	case TTY_LED_CNT:
> +	default:
> +		return sprintf(buf, "[%s] %s %s %s %s\n", mode[TTY_LED_CNT],
> +				mode[TTY_LED_CTS], mode[TTY_LED_DSR],
> +				mode[TTY_LED_CAR], mode[TTY_LED_RNG]);

Can't we do the above in a loop easier?

> +static ssize_t 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;
> +
> +	/* Check for new line in string*/
> +	if (size > 0 && buf[size - 1] == '\n')
> +		size -= 1;
> +
> +	if (strncmp(buf, mode[TTY_LED_CTS], size) == 0)
> +		tty_mode = TTY_LED_CTS;
> +	else if (strncmp(buf, mode[TTY_LED_DSR], size) == 0)
> +		tty_mode = TTY_LED_DSR;
> +	else if (strncmp(buf, mode[TTY_LED_CAR], size) == 0)
> +		tty_mode = TTY_LED_CAR;
> +	else if (strncmp(buf, mode[TTY_LED_RNG], size) == 0)
> +		tty_mode = TTY_LED_RNG;
> +	else if (strncmp(buf, mode[TTY_LED_CNT], size) == 0)
> +		tty_mode = TTY_LED_CNT;
> +	else
> +		return -EINVAL;

Again, a loop?

> +
> +	mutex_lock(&trigger_data->mutex);
> +	trigger_data->mode = tty_mode;
> +	mutex_unlock(&trigger_data->mutex);
> +
> +	return ret;
> +}
> +static DEVICE_ATTR_RW(mode);
> +
>   static ssize_t ttyname_show(struct device *dev,
>   			    struct device_attribute *attr, char *buf)
>   {
> @@ -76,6 +161,18 @@ 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);

So what about negative values = errors?

> +	if (status & flag)

They really might hit here.

> +		led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
> +	else
> +		led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
> +}
> +


thanks,
-- 
js
suse labs