usb_ep_clear_halt(9) [suse man page]

USB_EP_CLEAR_HALT(9)					      Kernel Mode Gadget API					      USB_EP_CLEAR_HALT(9)

NAME

       usb_ep_clear_halt - clears endpoint halt, and resets toggle

SYNOPSIS

       int usb_ep_clear_halt(struct usb_ep * ep);

ARGUMENTS

       ep
	   the bulk or interrupt endpoint being reset

DESCRIPTION

       Use this when responding to the standard usb "set interface" request, for endpoints that aren't reconfigured, after clearing any other
       state in the endpoint's i/o queue.

       Returns zero, or a negative error code. On success, this call clears the underlying hardware state reflecting endpoint halt and data
       toggle. Note that some hardware can't support this request (like pxa2xx_udc), and accordingly can't correctly implement interface
       altsettings.

AUTHOR

       David Brownell <dbrownell@users.sourceforge.net>
	   Author.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010						      USB_EP_CLEAR_HALT(9)

STRUCT 
USB_REQUEST(9)					      Kernel Mode Gadget API					     STRUCT USB_REQUEST(9)

NAME

       struct_usb_request - describes one i/o request

SYNOPSIS

       struct usb_request {
	 void * buf;
	 unsigned length;
	 dma_addr_t dma;
	 unsigned no_interrupt:1;
	 unsigned zero:1;
	 unsigned short_not_ok:1;
	 void (* complete) (struct usb_ep *ep,struct usb_request *req);
	 void * context;
	 struct list_head list;
	 int status;
	 unsigned actual;
       };

MEMBERS

       buf
	   Buffer used for data. Always provide this; some controllers only use PIO, or don't use DMA for some endpoints.

       length
	   Length of that data

       dma
	   DMA address corresponding to 'buf'. If you don't set this field, and the usb controller needs one, it is responsible for mapping and
	   unmapping the buffer.

       no_interrupt
	   If true, hints that no completion irq is needed. Helpful sometimes with deep request queues that are handled directly by DMA
	   controllers.

       zero
	   If true, when writing data, makes the last packet be "short" by adding a zero length packet as needed;

       short_not_ok
	   When reading data, makes short packets be treated as errors (queue stops advancing till cleanup).

       complete
	   Function called when request completes, so this request and its buffer may be re-used. The function will always be called with
	   interrupts disabled, and it must not sleep. Reads terminate with a short packet, or when the buffer fills, whichever comes first. When
	   writes terminate, some data bytes will usually still be in flight (often in a hardware fifo). Errors (for reads or writes) stop the
	   queue from advancing until the completion function returns, so that any transfers invalidated by the error may first be dequeued.

       context
	   For use by the completion callback

       list
	   For use by the gadget driver.

       status
	   Reports completion code, zero or a negative errno. Normally, faults block the transfer queue from advancing until the completion
	   callback returns. Code "-ESHUTDOWN" indicates completion caused by device disconnect, or when the driver disabled the endpoint.

       actual
	   Reports bytes transferred to/from the buffer. For reads (OUT transfers) this may be less than the requested length. If the short_not_ok
	   flag is set, short reads are treated as errors even when status otherwise indicates successful completion. Note that for writes (IN
	   transfers) some data bytes may still reside in a device-side FIFO when the request is reported as complete.

DESCRIPTION

       These are allocated/freed through the endpoint they're used with. The hardware's driver can add extra per-request data to the memory it
       returns, which often avoids separate memory allocations (potential failures), later when the request is queued.

       Request flags affect request handling, such as whether a zero length packet is written (the "zero" flag), whether a short read should be
       treated as an error (blocking request queue advance, the "short_not_ok" flag), or hinting that an interrupt is not required (the
       "no_interrupt" flag, for use with deep request queues).

       Bulk endpoints can use any size buffers, and can also be used for interrupt transfers. interrupt-only endpoints can be much less
       functional.

NOTE

       this is analagous to 'struct urb' on the host side, except that it's thinner and promotes more pre-allocation.

AUTHOR

       David Brownell <dbrownell@users.sourceforge.net>
	   Author.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010						     STRUCT USB_REQUEST(9)