usb_clear_halt(9) [centos man page]

USB_CLEAR_HALT(9)						   USB Core APIs						 USB_CLEAR_HALT(9)

NAME

       usb_clear_halt - tells device to clear endpoint halt/stall condition

SYNOPSIS

       int usb_clear_halt(struct usb_device * dev, int pipe);

ARGUMENTS

       dev
	   device whose endpoint is halted

       pipe
	   endpoint "pipe" being cleared

CONTEXT

       !in_interrupt ()

DESCRIPTION

       This is used to clear halt conditions for bulk and interrupt endpoints, as reported by URB completion status. Endpoints that are halted are
       sometimes referred to as being "stalled". Such endpoints are unable to transmit or receive data until the halt status is cleared. Any URBs
       queued for such an endpoint should normally be unlinked by the driver before clearing the halt condition, as described in sections 5.7.5
       and 5.8.5 of the USB 2.0 spec.

       Note that control and isochronous endpoints don't halt, although control endpoints report "protocol stall" (for unsupported requests) using
       the same status code used to report a true stall.

       This call is synchronous, and may not be used in an interrupt context.

RETURN

       Zero on success, or else the status code returned by the underlying usb_control_msg call.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							 USB_CLEAR_HALT(9)

USB_BULK_MSG(9) 						   USB Core APIs						   USB_BULK_MSG(9)

NAME

       usb_bulk_msg - Builds a bulk urb, sends it off and waits for completion

SYNOPSIS

       int usb_bulk_msg(struct usb_device * usb_dev, unsigned int pipe, void * data, int len, int * actual_length, int timeout);

ARGUMENTS

       usb_dev
	   pointer to the usb device to send the message to

       pipe
	   endpoint "pipe" to send the message to

       data
	   pointer to the data to send

       len
	   length in bytes of the data to send

       actual_length
	   pointer to a location to put the actual length transferred in bytes

       timeout
	   time in msecs to wait for the message to complete before timing out (if 0 the wait is forever)

CONTEXT

       !in_interrupt ()

DESCRIPTION

       This function sends a simple bulk message to a specified endpoint and waits for the message to complete, or timeout.

       If successful, it returns 0, otherwise a negative error number. The number of actual bytes transferred will be stored in the actual_length
       paramater.

       Don't use this function from within an interrupt context, like a bottom half handler. If you need an asynchronous message, or need to send
       a message from within interrupt context, use usb_submit_urb If a thread in your driver uses this call, make sure your disconnect method can
       wait for it to complete. Since you don't have a handle on the URB used, you can't cancel the request.

       Because there is no usb_interrupt_msg and no USBDEVFS_INTERRUPT ioctl, users are forced to abuse this routine by using it to submit URBs
       for interrupt endpoints. We will take the liberty of creating an interrupt URB (with the default interval) if the target is an interrupt
       endpoint.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010							   USB_BULK_MSG(9)