diff options
| author | Michal Sojka <sojka@merica.cz> | 2014-09-24 22:43:21 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-09-25 17:05:12 +0200 |
| commit | 0cfbd328d60f85b0dcf66df61a3615e9a8e5d4e4 (patch) | |
| tree | bae04eca569eecee711f27fd2e1d08e6f837ebbe /include/linux/usb.h | |
| parent | aa923ef1aa39473b7d1f413c73a3e1d19ebde65d (diff) | |
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 'include/linux/usb.h')
| -rw-r--r-- | include/linux/usb.h | 12 |
1 files changed, 12 insertions, 0 deletions
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 |