linux-kernel - Re: [PATCH v6 4/4] usb: Add LED triggers for USB activity

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Date:	Wed, 24 Sep 2014 15:56:27 -0500
From:	Felipe Balbi <balbi@...com>
To:	Michal Sojka <sojka@...ica.cz>
CC:	<linux-usb@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Bryan Wu <cooloney@...il.com>, Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux LED Subsystem <linux-leds@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <michal.vokac@...ap.cz>
Subject: Re: [PATCH v6 4/4] usb: Add LED triggers for USB activity

Hi,

On Wed, Sep 24, 2014 at 10:43:21PM +0200, Michal Sojka wrote:
> With this patch, USB activity can be signaled by blinking a LED. There
> are two triggers, one for activity on USB host and one for USB gadget.
> 
> Both triggers should work with all host/device controllers. Tested only
> with musb.
> 
> Performace: I measured performance overheads on ARM Cortex-A8 (TI
> AM335x) running on 600 MHz.
> 
> Duration of usb_led_activity():
> - with no LED attached to the trigger:        2 ± 1 µs
> - with one GPIO LED attached to the trigger:  2 ± 1 µs or 8 ± 2 µs (two peaks in histogram)
> 
> Duration of functions calling usb_led_activity() (with this patch
> applied and no LED attached to the trigger):
> - __usb_hcd_giveback_urb():    10 - 25 µs
> - usb_gadget_giveback_request(): 2 - 6 µs
>
> Signed-off-by: Michal Sojka <sojka@...ica.cz>
> ---
>  drivers/usb/Kconfig               | 10 +++++++
>  drivers/usb/common/Makefile       |  1 +
>  drivers/usb/common/led.c          | 57 +++++++++++++++++++++++++++++++++++++++
>  drivers/usb/core/hcd.c            |  2 ++
>  drivers/usb/gadget/udc/udc-core.c |  4 +++
>  include/linux/usb.h               | 12 +++++++++
>  6 files changed, 86 insertions(+)
>  create mode 100644 drivers/usb/common/led.c
> 
> diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
> index cf1b19b..ae481c3 100644
> --- a/drivers/usb/Kconfig
> +++ b/drivers/usb/Kconfig
> @@ -149,4 +149,14 @@ source "drivers/usb/phy/Kconfig"
>  
>  source "drivers/usb/gadget/Kconfig"
>  
> +config USB_LED_TRIG
> +	bool "USB LED Triggers"
> +	depends on LEDS_CLASS && USB_COMMON && LEDS_TRIGGERS
> +	help
> +	  This option adds LED triggers for USB host and/or gadget activity.
> +
> +	  Say Y here if you are working on a system with led-class supported
> +	  LEDs and you want to use them as activity indicators for USB host or
> +	  gadget.
> +
>  endif # USB_SUPPORT
> diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
> index 052c120..ca2f8bd 100644
> --- a/drivers/usb/common/Makefile
> +++ b/drivers/usb/common/Makefile
> @@ -4,5 +4,6 @@
>  
>  obj-$(CONFIG_USB_COMMON)	  += usb-common.o
>  usb-common-y			  += common.o
> +usb-common-$(CONFIG_USB_LED_TRIG) += led.o
>  
>  obj-$(CONFIG_USB_OTG_FSM) += usb-otg-fsm.o
> diff --git a/drivers/usb/common/led.c b/drivers/usb/common/led.c
> new file mode 100644
> index 0000000..df23da0
> --- /dev/null
> +++ b/drivers/usb/common/led.c
> @@ -0,0 +1,57 @@
> +/*
> + * LED Triggers for USB Activity
> + *
> + * Copyright 2014 Michal Sojka <sojka@...ica.cz>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/leds.h>
> +#include <linux/usb.h>
> +
> +#define BLINK_DELAY 30
> +
> +static unsigned long usb_blink_delay = BLINK_DELAY;
> +
> +DEFINE_LED_TRIGGER(ledtrig_usb_gadget);
> +DEFINE_LED_TRIGGER(ledtrig_usb_host);
> +
> +void usb_led_activity(enum usb_led_event ev)
> +{
> +	struct led_trigger *trig = NULL;
> +
> +	switch (ev) {
> +	case USB_LED_EVENT_GADGET:
> +		trig = ledtrig_usb_gadget;
> +		break;
> +	case USB_LED_EVENT_HOST:
> +		trig = ledtrig_usb_host;
> +		break;
> +	}
> +	/* led_trigger_blink_oneshot() handles trig == NULL gracefully */
> +	led_trigger_blink_oneshot(trig, &usb_blink_delay, &usb_blink_delay, 0);
> +}
> +EXPORT_SYMBOL_GPL(usb_led_activity);
> +
> +

minor nit: one blank line only. other than that, this looks pretty good
to me:

Acked-by: Felipe Balbi <balbi@...com>

-- 
balbi

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