Re: [PATCH V3] leds: trigger: Introduce an USB port trigger

[Matthias Brugger <mbrugger@suse.com>]

On 24/08/16 00:03, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@milecki.pl>
>
> This commit adds a new trigger responsible for turning on LED when USB
> device gets connected to the specified USB port. This can can useful for
> various home routers that have USB port(s) and a proper LED telling user
> a device is connected.
>
> The trigger gets its documentation file but basically it just requires
> specifying USB port in a Linux format (e.g. echo 1-1 > new_port).
>
> During work on this trigger there was a plan to add DT bindings for it,
> but there wasn't an agreement on the format yet. This can be worked on
> later, a sysfs interface is needed anyway for platforms not using DT.
>
> Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
> ---
> V2: Trying to add DT support, idea postponed as it will take more time
>     to discuss the bindings.
> V3: Fix typos in commit and Documentation (thanks Jacek!)
>     Use "ports" sysfs file for adding and removing USB ports (thx Jacek)
>     Check if there is USB device connected after adding new USB port
>     Fix memory leak or two
>
> Felipe: I'd like to ask for your Ack before having this patch pushed.
> ---
>  Documentation/leds/ledtrig-usbport.txt |  49 +++++++
>  drivers/leds/trigger/Kconfig           |   8 ++
>  drivers/leds/trigger/Makefile          |   1 +
>  drivers/leds/trigger/ledtrig-usbport.c | 253 +++++++++++++++++++++++++++++++++
>  4 files changed, 311 insertions(+)
>  create mode 100644 Documentation/leds/ledtrig-usbport.txt
>  create mode 100644 drivers/leds/trigger/ledtrig-usbport.c
>
> diff --git a/Documentation/leds/ledtrig-usbport.txt b/Documentation/leds/ledtrig-usbport.txt
> new file mode 100644
> index 0000000..fa42227
> --- /dev/null
> +++ b/Documentation/leds/ledtrig-usbport.txt
> @@ -0,0 +1,49 @@
> +USB port LED trigger
> +====================
> +
> +This LED trigger can be used for signalling to the user a presence of USB device
> +in a given port. It simply turns on LED when device appears and turns it off
> +when it disappears.
> +
> +It requires specifying a list of USB ports that should be observed. Used format
> +matches Linux kernel format and consists of a root hub number and a hub port
> +separated by a dash (e.g. 3-1).
> +
> +It is also possible to handle devices with internal hubs (that are always
> +connected to the root hub). User can simply specify internal hub ports then
> +(e.g. 1-1.1, 1-1.2, etc.).
> +
> +Please note that this trigger allows assigning multiple USB ports to a single
> +LED. This can be useful in two cases:
> +
> +1) Device with single USB LED and few physical ports
> +
> +In such a case LED will be turned on as long as there is at least one connected
> +USB device.
> +
> +2) Device with a physical port handled by few controllers
> +
> +Some devices have e.g. one controller per PHY standard. E.g. USB 3.0 physical
> +port may be handled by ohci-platform, ehci-platform and xhci-hcd. If there is
> +only one LED user will most likely want to assign ports from all 3 hubs.
> +
> +
> +This trigger can be activated from user space on led class devices as shown
> +below:
> +
> +  echo usbport > trigger
> +
> +This adds the following sysfs attributes to the LED:
> +
> +  ports - Reading it lists all USB ports assigned to the trigger. Writing USB
> +	  port number to it will make this driver start observing it. It's also
> +	  possible to remove USB port from observable list by writing it with a
> +	  "-" prefix.
> +
> +Example use-case:
> +
> +  echo usbport > trigger
> +  echo 4-1 > ports
> +  echo 2-1 > ports
> +  echo -4-1 > ports
> +  cat ports
> diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
> index 3f9ddb9..bdd6fd2 100644
> --- a/drivers/leds/trigger/Kconfig
> +++ b/drivers/leds/trigger/Kconfig
> @@ -126,4 +126,12 @@ config LEDS_TRIGGER_PANIC
>  	  a different trigger.
>  	  If unsure, say Y.
>
> +config LEDS_TRIGGER_USBPORT
> +	tristate "USB port LED trigger"
> +	depends on LEDS_TRIGGERS && USB
> +	help
> +	  This allows LEDs to be controlled by USB events. Enabling this option
> +	  allows specifying list of USB ports that should turn on LED when some
> +	  USB device gets connected.
> +
>  endif # LEDS_TRIGGERS
> diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
> index a72c43c..56e1741 100644
> --- a/drivers/leds/trigger/Makefile
> +++ b/drivers/leds/trigger/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o
>  obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT)	+= ledtrig-transient.o
>  obj-$(CONFIG_LEDS_TRIGGER_CAMERA)	+= ledtrig-camera.o
>  obj-$(CONFIG_LEDS_TRIGGER_PANIC)	+= ledtrig-panic.o
> +obj-$(CONFIG_LEDS_TRIGGER_USBPORT)	+= ledtrig-usbport.o
> diff --git a/drivers/leds/trigger/ledtrig-usbport.c b/drivers/leds/trigger/ledtrig-usbport.c
> new file mode 100644
> index 0000000..7f5237c
> --- /dev/null
> +++ b/drivers/leds/trigger/ledtrig-usbport.c
> @@ -0,0 +1,253 @@
> +/*
> + * USB port LED trigger
> + *
> + * Copyright (C) 2016 Rafał Miłecki <rafal@milecki@pl>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or (at
> + * your option) any later version.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/leds.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/usb.h>
> +#include "../leds.h"
> +
> +struct usbport_trig_port {
> +	char *name;
> +	struct list_head list;
> +};
> +
> +struct usbport_trig_data {
> +	struct led_classdev *led_cdev;
> +	struct list_head ports;
> +	struct notifier_block nb;
> +	int count; /* Amount of connected matching devices */
> +};
> +
> +/* Helpers */
> +
> +/**
> + * usbport_trig_usb_dev_observed - Check if dev is connected to observerd port
> + */
> +static bool usbport_trig_usb_dev_observed(struct usbport_trig_data *usbport_data,
> +					  struct usb_device *usb_dev)
> +{
> +	struct usbport_trig_port *port;
> +	const char *name = dev_name(&usb_dev->dev);
> +
> +	list_for_each_entry(port, &usbport_data->ports, list) {
> +		if (!strcmp(port->name, name))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +static int usbport_trig_usb_dev_check(struct usb_device *usb_dev, void *data)
> +{
> +	struct usbport_trig_data *usbport_data = data;
> +
> +	if (usbport_trig_usb_dev_observed(usbport_data, usb_dev))
> +		usbport_data->count++;
> +
> +	return 0;
> +}
> +
> +/**
> + * usbport_trig_update_count - Recalculate amount of connected matching devices
> + */
> +static void usbport_trig_update_count(struct usbport_trig_data *usbport_data)
> +{
> +	struct led_classdev *led_cdev = usbport_data->led_cdev;
> +
> +	usbport_data->count = 0;
> +	usb_for_each_dev(usbport_data, usbport_trig_usb_dev_check);
> +	led_set_brightness_nosleep(led_cdev,
> +				   usbport_data->count ? LED_FULL : LED_OFF);
> +}
> +
> +/* Device attr */
> +
> +static ssize_t ports_show(struct device *dev, struct device_attribute *attr,
> +			  char *buf)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct usbport_trig_data *usbport_data = led_cdev->trigger_data;
> +	struct usbport_trig_port *port;
> +	ssize_t ret = 0;
> +	int len;
> +
> +	list_for_each_entry(port, &usbport_data->ports, list) {
> +		len = sprintf(buf + ret, "%s\n", port->name);
> +		if (len >= 0)
> +			ret += len;
> +	}
> +
> +	return ret;
> +}
> +
> +static ssize_t ports_store(struct device *dev, struct device_attribute *attr,
> +			   const char *buf, size_t size)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct usbport_trig_data *usbport_data = led_cdev->trigger_data;
> +	struct usbport_trig_port *port;
> +	bool add = true;
> +	size_t len;
> +
> +	len = strlen(buf);
> +	/* See if this is add or remove request */
> +	if (len && buf[0] == '-') {
> +		add = false;
> +		buf++;
> +		len--;
> +	}
> +	/* For user convenience trim line break */
> +	if (len && buf[len - 1] == '\n')
> +		len--;
> +	if (!len)
> +		return -EINVAL;
> +
> +	if (add) {
> +		port = kzalloc(sizeof(*port), GFP_KERNEL);
> +		if (!port)
> +			return -ENOMEM;
> +		port->name = kzalloc(strlen(buf), GFP_KERNEL);
> +		if (!port->name) {
> +			kfree(port);
> +			return -ENOMEM;
> +		}
> +		strncpy(port->name, buf, len);
> +
> +		list_add_tail(&port->list, &usbport_data->ports);
> +
> +		usbport_trig_update_count(usbport_data);
> +	} else {
> +		struct usbport_trig_port *tmp;
> +		bool found = false;
> +
> +		list_for_each_entry_safe(port, tmp, &usbport_data->ports,
> +					 list) {
> +			if (strlen(port->name) == len &&
> +			    !strncmp(port->name, buf, len)) {
> +				list_del(&port->list);
> +				kfree(port->name);
> +				kfree(port);
> +
> +				found = true;
> +				break;
> +			}
> +		}
> +
> +		if (!found)
> +			return -ENOENT;
> +	}
> +
> +	usbport_trig_update_count(usbport_data);
> +
> +	return size;
> +}
> +
> +static DEVICE_ATTR(ports, S_IRUSR | S_IWUSR, ports_show, ports_store);
> +
> +/* Init, exit, etc. */
> +
> +static int usbport_trig_notify(struct notifier_block *nb, unsigned long action,
> +			       void *data)
> +{
> +	struct usbport_trig_data *usbport_data =
> +		container_of(nb, struct usbport_trig_data, nb);
> +	struct led_classdev *led_cdev = usbport_data->led_cdev;
> +
> +	switch (action) {
> +	case USB_DEVICE_ADD:
> +		if (usbport_trig_usb_dev_observed(usbport_data, data)) {

Maybe we should switch this and fist see if the usbport is observed 
before evaluating the action. Also cast data to "struct usb_device *" to 
make that clear.

> +			if (usbport_data->count++ == 0)

I'm a bit puzzled. I think:
if (++usbport_data->count > 0)
makes this more consistent with the remove case.

> +				led_set_brightness_nosleep(led_cdev, LED_FULL);
> +		}
> +		break;
> +	case USB_DEVICE_REMOVE:
> +		if (usbport_trig_usb_dev_observed(usbport_data, data)) {
> +			if (--usbport_data->count == 0)
> +				led_set_brightness_nosleep(led_cdev, LED_OFF);
> +		}
> +		break;
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +static void usbport_trig_activate(struct led_classdev *led_cdev)
> +{
> +	struct usbport_trig_data *usbport_data;
> +	int err;
> +
> +	usbport_data = kzalloc(sizeof(*usbport_data), GFP_KERNEL);
> +	if (!usbport_data)
> +		return;
> +	usbport_data->led_cdev = led_cdev;
> +	INIT_LIST_HEAD(&usbport_data->ports);
> +	usbport_data->nb.notifier_call = usbport_trig_notify,
> +	led_cdev->trigger_data = usbport_data;
> +
> +	err = device_create_file(led_cdev->dev, &dev_attr_ports);
> +	if (err)
> +		goto err_free;
> +
> +	usb_register_notify(&usbport_data->nb);
> +
> +	led_cdev->activated = true;
> +	return;
> +
> +err_free:
> +	kfree(usbport_data);
> +}
> +
> +static void usbport_trig_deactivate(struct led_classdev *led_cdev)
> +{
> +	struct usbport_trig_data *usbport_data = led_cdev->trigger_data;
> +	struct usbport_trig_port *port, *tmp;
> +
> +	if (!led_cdev->activated)
> +		return;
> +
> +	usb_unregister_notify(&usbport_data->nb);
> +
> +	list_for_each_entry_safe(port, tmp, &usbport_data->ports, list) {
> +		list_del(&port->list);
> +		kfree(port->name);
> +		kfree(port);
> +	}
> +
> +	device_remove_file(led_cdev->dev, &dev_attr_ports);
> +	kfree(usbport_data);
> +
> +	led_cdev->activated = false;
> +}
> +
> +static struct led_trigger usbport_led_trigger = {
> +	.name     = "usbport",
> +	.activate = usbport_trig_activate,
> +	.deactivate = usbport_trig_deactivate,
> +};
> +
> +static int __init usbport_trig_init(void)
> +{
> +	return led_trigger_register(&usbport_led_trigger);
> +}
> +
> +static void __exit usbport_trig_exit(void)
> +{
> +	led_trigger_unregister(&usbport_led_trigger);
> +}
> +
> +module_init(usbport_trig_init);
> +module_exit(usbport_trig_exit);
> +
> +MODULE_AUTHOR("Rafał Miłecki <rafal@milecki@pl>");

Nit: rafal@milecki.pl

Regards,
Matthias

> +MODULE_DESCRIPTION("USB port trigger");
> +MODULE_LICENSE("GPL");
>