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
8 unsigned int page_size;
9
10 static 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 */
36 ssize_t readn(int fd, void *buf, size_t n)
37 {
38 return ion(true, fd, buf, n);
39 }
40
41 ssize_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 */
64 ssize_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
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