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
41ssize_t preadn(int fd, void *buf, size_t n, off_t offs)
42{
43	size_t left = n;
44
45	while (left) {
46		ssize_t ret = pread(fd, buf, left, offs);
47
48		if (ret < 0 && errno == EINTR)
49			continue;
50		if (ret <= 0)
51			return ret;
52
53		left -= ret;
54		buf  += ret;
55		offs += ret;
56	}
57
58	return n;
59}
60
61/*
62 * Write exactly 'n' bytes or return an error.
63 */
64ssize_t writen(int fd, const void *buf, size_t n)
65{
66	/* ion does not modify buf. */
67	return ion(false, fd, (void *)buf, n);
68}
69