diff options
| author | Michal Sojka <sojka@merica.cz> | 2014-09-25 00:43:21 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-09-25 19:05:12 +0400 |
| commit | 0cfbd328d60f85b0dcf66df61a3615e9a8e5d4e4 (patch) | |
| tree | bae04eca569eecee711f27fd2e1d08e6f837ebbe /drivers/usb/common | |
| parent | aa923ef1aa39473b7d1f413c73a3e1d19ebde65d (diff) | |
| download | linux-0cfbd328d60f85b0dcf66df61a3615e9a8e5d4e4.tar.xz | |
usb: Add LED triggers for USB activity
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>
Acked-by: Felipe Balbi <balbi@ti.com>
Tested-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/common')
| -rw-r--r-- | drivers/usb/common/Makefile | 1 | ||||
| -rw-r--r-- | drivers/usb/common/led.c | 57 |
2 files changed, 58 insertions, 0 deletions
diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile index 052c12069c24..ca2f8bd0e431 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 000000000000..df23da00a901 --- /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); + + +static int __init ledtrig_usb_init(void) +{ + led_trigger_register_simple("usb-gadget", &ledtrig_usb_gadget); + led_trigger_register_simple("usb-host", &ledtrig_usb_host); + return 0; +} + +static void __exit ledtrig_usb_exit(void) +{ + led_trigger_unregister_simple(ledtrig_usb_gadget); + led_trigger_unregister_simple(ledtrig_usb_host); +} + +module_init(ledtrig_usb_init); +module_exit(ledtrig_usb_exit); |