Hi all,
We are successfully using the USB Gadget HID driver (g_hid) with a MUSB device controller on a 2.6.32 kernel to communicate with a USB host. Now we want to add the wakeup feature so that the device can wakeup the host if the USB bus has been suspended. We have found a simple and working method; but does anyone know of a better/standard/more robust way of doing this?
hid.c already contains specifics on our HID descriptors, so we add the feature to the report descriptor:
--- drivers/usb/gadget/hid.c
+++ drivers/usb/gadget/hid.c
@@ -152,7 +152,7 @@
.bind = do_config,
.bConfigurationValue = 1,
/* .iConfiguration = DYNAMIC */
- .bmAttributes = USB_CONFIG_ATT_SELFPOWER,
+ .bmAttributes = USB_CONFIG_ATT_SELFPOWER | USB_CONFIG_ATT_WAKEUP,
};
f_hid.c reads data from userspace and writes to the endpoint. All sent data is treated equal (this is of course application dependant) and should wakeup the host if sleeping:
--- drivers/usb/gadget/f_hid.c
+++ drivers/usb/gadget/f_hid.c
@@ -240,6 +240,8 @@
hidg->req->context = hidg;
hidg->write_pending = 1;
+ usb_gadget_wakeup(hidg->func.config->cdev->gadget);
+
status = usb_ep_queue(hidg->in_ep, hidg->req, GFP_ATOMIC);
if (status < 0) {
//ERROR(hidg->func.config->cdev,
The usb_gadget_wakeup() lies in the hotpath, but the MUSB controller driver will only send the resume signal in case the bus is suspended and the host does support wakeup (musb_gadget.c:musb_gadget_wakeup()). Alternatively, one could signal the MUSB controller directly from userspace, but that will also lie in the hotpath and has even more overhead.
echo 1 > /sys/devices/platform/musb_hdrc/srp
Does anyone have any suggestions on a better location for this kind of wakeup functionality? In the MUSB controller driver? In the composite driver?
Regards,
Pablo
-------------------------
Pablo Cases, M.Sc.
Development Engineer Software
FlatFrog Laboratories AB
Magistratsvägen 10
22643 Lund
Sweden
Tel: +46 708 393816
Mail: pc@xxxxxxxxxxxx
Web: www.flatfrog.com
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