USBD_TRANSFER(9) Kernel Developer's Manual USBD_TRANSFER(9)

usbd_setup_xfer, usbd_transfer — submit USB data transfers

#include <dev/usb/usb.h>
#include <dev/usb/usbdi.h>

void
usbd_setup_xfer(struct usbd_xfer *xfer, struct usbd_pipe *pipe, void *priv, void *buffer, uint32_t length, uint16_t flags, uint32_t timeout, usbd_callback callback);

usbd_status
usbd_transfer(struct usbd_xfer *xfer);

These functions provide a controller independent mechanism to perform USB data transfers. They make use of a pipe created by usbd_open_pipe(9) or usbd_open_pipe_intr(9).

The function () is used to initialize the structure pointed to by xfer, describing an individual transfer to submit. It takes the following arguments:

xfer
A pointer to an existing structure describing a transfer.
pipe
A pointer to a pipe associated with the endpoint for the transfer.
priv
A pointer to a private cookie untouched by the USB stack for reuse in the callback.
buffer
A pointer to the data buffer.
length
The total length of the data to read or write.
flags
The characteristics of the transfer:
Do not copy data between buffer and the DMA buffer.
Causes usbd_transfer() to sleep until the I/O transfer is complete or the timeout expires.
Do not report short reads, when the length of the data read is lower than length, as errors.
Submit a supplementary zero length packet at the end of the written data. Some requests may need such packets in order to be properly terminated.
Used in conjunction with the USBD_SYNCHRONOUS flag to pass the PCATCH flag to tsleep(9) in order to check for signals before and after sleeping.
timeout
Timeout of the transfer in milliseconds.
callback
A routine invoked upon completion of the transfer whether successful or not.

The function () is used to submit the USB transfer described by xfer to the corresponding usb(4) host controller to perform I/O with devices.

usbd_setup_xfer() can be called during autoconf, from process context, or from interrupt context.

usbd_transfer() can be called during autoconf, from process context, or from interrupt context if USBD_SYNCHRONOUS has not been passed via flags.

ehci(4), ohci(4), uhci(4), usb(4), tsleep(9), usbd_open_pipe(9), usbd_open_pipe_intr(9)

May 4, 2015 OpenBSD 7.5