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SubjectRe: [PATCH v3 3/3] leds: trigger: implement a tty trigger
On Tue, Dec 17, 2019 at 04:27:24PM +0100, Greg Kroah-Hartman wrote:
> On Tue, Dec 17, 2019 at 04:07:36PM +0100, Uwe Kleine-König wrote:
> > Usage is as follows:
> >
> > myled=ledname
> > tty=ttyS0
> >
> > echo tty > /sys/class/leds/$myled/trigger
> > cat /sys/class/tty/$tty/dev > /sys/class/leds/$myled/dev
>
> Is this the correct instructions? Aren't you looking for a major/minor
> number instead in your sysfs file?

This is correct, yes, at least it works as intended on my machine.

/sys/class/tty/$tty/dev produces $major:$minor and that's what the
led-trigger consumes.

> > . When this new trigger is active it periodically checks the tty's
> > statistics and when it changed since the last check the led is flashed
> > once.
> >
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > ---
> > drivers/leds/trigger/Kconfig | 7 ++
> > drivers/leds/trigger/Makefile | 1 +
> > drivers/leds/trigger/ledtrig-tty.c | 159 +++++++++++++++++++++++++++++
> > 3 files changed, 167 insertions(+)
> > create mode 100644 drivers/leds/trigger/ledtrig-tty.c
> >
> > diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
> > index ce9429ca6dde..40ff08c93f56 100644
> > --- a/drivers/leds/trigger/Kconfig
> > +++ b/drivers/leds/trigger/Kconfig
> > @@ -144,4 +144,11 @@ config LEDS_TRIGGER_AUDIO
> > the audio mute and mic-mute changes.
> > If unsure, say N
> >
> > +config LEDS_TRIGGER_TTY
> > + tristate "LED Trigger for TTY devices"
> > + depends on TTY
> > + help
> > + This allows LEDs to be controlled by activity on ttys which includes
> > + serial devices like /dev/ttyS0.
> > +
> > endif # LEDS_TRIGGERS
> > diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
> > index 733a83e2a718..25c4db97cdd4 100644
> > --- a/drivers/leds/trigger/Makefile
> > +++ b/drivers/leds/trigger/Makefile
> > @@ -15,3 +15,4 @@ obj-$(CONFIG_LEDS_TRIGGER_PANIC) += ledtrig-panic.o
> > obj-$(CONFIG_LEDS_TRIGGER_NETDEV) += ledtrig-netdev.o
> > obj-$(CONFIG_LEDS_TRIGGER_PATTERN) += ledtrig-pattern.o
> > obj-$(CONFIG_LEDS_TRIGGER_AUDIO) += ledtrig-audio.o
> > +obj-$(CONFIG_LEDS_TRIGGER_TTY) += ledtrig-tty.o
> > diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
> > new file mode 100644
> > index 000000000000..0157aa0b2ce3
> > --- /dev/null
> > +++ b/drivers/leds/trigger/ledtrig-tty.c
> > @@ -0,0 +1,159 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <linux/leds.h>
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/tty.h>
> > +#include <uapi/linux/serial.h>
> > +
> > +struct ledtrig_tty_data {
> > + struct led_classdev *led_cdev;
> > + struct delayed_work dwork;
> > + struct tty_struct *tty;
> > + dev_t device;
> > + int rx, tx;
> > +};
> > +
> > +static void ledtrig_tty_halt(struct ledtrig_tty_data *trigger_data)
> > +{
> > + cancel_delayed_work_sync(&trigger_data->dwork);
> > +}
> > +
> > +static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
> > +{
> > + if (!trigger_data->tty)
> > + return;
> > +
> > + schedule_delayed_work(&trigger_data->dwork, 0);
> > +}
> > +
> > +static ssize_t dev_show(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
> > + ssize_t len = 0;
> > +
> > + if (trigger_data->tty)
> > + len = sprintf(buf, "%u\n", trigger_data->device);
>
> Will that print a dev_t in a format that userspace can make sense of it?
> Should you split it up with MAJOR:MINOR instead?

Ah, yes, this needs fixing to match the format that is used in .store.

> > +
> > + return len;
> > +}
> > +
> > +static ssize_t dev_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);
> > + struct tty_struct *tty;
> > + unsigned major, minor;
> > + int ret;
> > +
> > + if (size == 0 || (size == 1 && buf[0] == '\n')) {
> > + tty = NULL;
> > + } else {
> > + ret = sscanf(buf, "%u:%u", &major, &minor);
> > + if (ret < 2) {
> > + dev_err(dev, "invalid value\n");
>
> Can I DoS the syslog with this? :)

Only if you can write to the sysfs file in which case you can DoS the
syslog anyhow :-)

> > + return -EINVAL;
> > + }
> > +
> > + tty = tty_kopen_shared(MKDEV(major, minor));
> > + if (IS_ERR(tty)) {
> > + dev_err(dev, "failed to open tty: %pe\n", tty);
>
> Same here, dev_dbg() perhaps?
>
> Other than these minor things, looks good to me.
>
> Your tty changes are fine, if I can get an ack from the led maintainers
> about a working patch 3, I'll be glad to take all 3 in my tree.

You'll get a v4 in a moment. Thanks for your prompt reviews.

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |

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