From 0cfbd328d60f85b0dcf66df61a3615e9a8e5d4e4 Mon Sep 17 00:00:00 2001 From: Michal Sojka Date: Wed, 24 Sep 2014 22:43:21 +0200 Subject: usb: Add LED triggers for USB activity MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Felipe Balbi Tested-by: Felipe Balbi Signed-off-by: Greg Kroah-Hartman --- include/linux/usb.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'include/linux/usb.h') diff --git a/include/linux/usb.h b/include/linux/usb.h index d2465bc0e73c..447a7e2fc19b 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -1862,6 +1862,18 @@ extern void usb_unregister_notify(struct notifier_block *nb); /* debugfs stuff */ extern struct dentry *usb_debug_root; +/* LED triggers */ +enum usb_led_event { + USB_LED_EVENT_HOST = 0, + USB_LED_EVENT_GADGET = 1, +}; + +#ifdef CONFIG_USB_LED_TRIG +extern void usb_led_activity(enum usb_led_event ev); +#else +static inline void usb_led_activity(enum usb_led_event ev) {} +#endif + #endif /* __KERNEL__ */ #endif -- cgit v1.2.3