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    SubjectRe: [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@merica.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@merica.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@ti.com>

    --
    balbi
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