1// SPDX-License-Identifier: GPL-2.0
 2#include <unistd.h>
 3#include <stdbool.h>
 4#include <errno.h>
 5#include <linux/kernel.h>
 6#include <internal/lib.h>
 7
 8unsigned int page_size;
 9
10static ssize_t ion(bool is_read, int fd, void *buf, size_t n)
11{
12	void *buf_start = buf;
13	size_t left = n;
14
15	while (left) {
16		/* buf must be treated as const if !is_read. */
17		ssize_t ret = is_read ? read(fd, buf, left) :
18					write(fd, buf, left);
19
20		if (ret < 0 && errno == EINTR)
21			continue;
22		if (ret <= 0)
23			return ret;
24
25		left -= ret;
26		buf  += ret;
27	}
28
29	BUG_ON((size_t)(buf - buf_start) != n);
30	return n;
31}
32
33/*
34 * Read exactly 'n' bytes or return an error.
35 */
36ssize_t readn(int fd, void *buf, size_t n)
37{
38	return ion(true, fd, buf, n);
39}
40
41/*
42 * Write exactly 'n' bytes or return an error.
43 */
44ssize_t writen(int fd, const void *buf, size_t n)
45{
46	/* ion does not modify buf. */
47	return ion(false, fd, (void *)buf, n);
48}