#include <gadget.h>

Data Fields
void *	buf

unsigned	length

dma_addr_t	dma

struct scatterlist *	sg

unsigned	num_sgs

unsigned	num_mapped_sgs

unsigned	stream_id:16

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

Detailed Description

struct usb_request - describes one i/o request : Buffer used for data. Always provide this; some controllers only use PIO, or don't use DMA for some endpoints. : 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. : a scatterlist for SG-capable controllers. : number of SG entries : number of SG entries mapped to DMA (internal) : Length of that data : The stream id, when USB3.0 bulk streams are being used : If true, hints that no completion irq is needed. Helpful sometimes with deep request queues that are handled directly by DMA controllers. : If true, when writing data, makes the last packet be "short" by adding a zero length packet as needed; : When reading data, makes short packets be treated as errors (queue stops advancing till cleanup). : 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. : For use by the completion callback : For use by the gadget driver. : 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. : 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.

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

Definition at line 90 of file gadget.h.