Multi Channel DMA Intel® FPGA IP for PCI Express User Guide

ID 683821
Date 8/19/2022
Public

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8.3.7. API List

Table 133.  Open
Function Description Prototype Return Values
Channel acquisition int open(const char *pathname, int flags, mode_t mode); File descriptor if successful, negative otherwise
Table 134.  Close
Function Description Prototype Return Values
Free the allocated channel int close(int fd); zero on success -1 otherwise, errno is set appropriately
Table 135.  Read
Function Description Prototype Return Values
Request submission for D2H transfer

ssize_t read(int fd, void *buf, int count);

buf : DMA buffer memory starting address

count: size of the DMA transfer data

number of bytes read if successful

-1 otherwise, errno is set appropriately

Table 136.  Write
Function Description Prototype Return Values
Request submission for H2D transfer

ssize_t write(int fd, void *buf, int count);

buf: DMA buffer memory starting address

count: size of the DMA transfer data

number of bytes written if successful -1 otherwise, errno is set appropriately
Table 137.  Readv
Function Description Prototype Return Values
Request submission for H2D transfer in batches ssize_t readv(int fd, const struct iovec *iov, int iovcnt);

On success, readv() return the number of bytes read

On error, -1 is returned, and errno is set appropriately

Table 138.  Writev
Function Description Prototype Return Values
Request submission for D2H transfer in batches ssize_t writev(int fd, const struct iovec *iov, int iovcnt);

On success, writev() return the number of bytes written

On error, -1 is returned, and errno is set appropriately

Table 139.  Poll
Function Description Prototype Return Values
Write Back poll

int poll(struct pollfd *fds, nfds_t nfds, int timeout);

Special support of events:
  • POLLIN: at least one descriptor queue slot free for D2H
  • POLLOUT: at least one descriptor queue slot free for H2D
  • POLLRDNORM: D2H descriptor queue is empty
  • POLLWRNORM: H2D descriptor queue is empty

On success, poll() returns a nonnegative value which is the number of elements in the pollfds whose revents fields have been set to a nonzero value (indicating an event or an error). A return value of zero indicates that the system call timed out before any file descriptors became read.

On error, -1 is returned, and errno is set to indicate the cause of the error.

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