Orange Pi5 kernel

// SPDX-License-Identifier: GPL-2.0
#include <unistd.h>
#include <stdbool.h>
#include <errno.h>
#include <linux/kernel.h>
#include <internal/lib.h>
 
unsigned int page_size;
 
static ssize_t ion(bool is_read, int fd, void *buf, size_t n)
{
<------>void *buf_start = buf;
<------>size_t left = n;
 
<------>while (left) {
<------><------>/* buf must be treated as const if !is_read. */
<------><------>ssize_t ret = is_read ? read(fd, buf, left) :
<------><------><------><------><------>write(fd, buf, left);
 
<------><------>if (ret < 0 && errno == EINTR)
<------><------><------>continue;
<------><------>if (ret <= 0)
<------><------><------>return ret;
 
<------><------>left -= ret;
<------><------>buf  += ret;
<------>}
 
<------>BUG_ON((size_t)(buf - buf_start) != n);
<------>return n;
}
 
/*
 * Read exactly 'n' bytes or return an error.
 */
ssize_t readn(int fd, void *buf, size_t n)
{
<------>return ion(true, fd, buf, n);
}
 
/*
 * Write exactly 'n' bytes or return an error.
 */
ssize_t writen(int fd, const void *buf, size_t n)
{
<------>/* ion does not modify buf. */
<------>return ion(false, fd, (void *)buf, n);
}