1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * printf.c:  Internal prom library printf facility.
4  *
5  * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
6  * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
7  * Copyright (c) 2002 Pete Zaitcev (zaitcev@yahoo.com)
8  *
9  * We used to warn all over the code: DO NOT USE prom_printf(),
10  * and yet people do. Anton's banking code was outputting banks
11  * with prom_printf for most of the 2.4 lifetime. Since an effective
12  * stick is not available, we deployed a carrot: an early printk
13  * through PROM by means of -p boot option. This ought to fix it.
14  * USE printk; if you need, deploy -p.
15  */
16 
17 #include <linux/kernel.h>
18 #include <linux/compiler.h>
19 #include <linux/spinlock.h>
20 
21 #include <asm/openprom.h>
22 #include <asm/oplib.h>
23 
24 #define CONSOLE_WRITE_BUF_SIZE	1024
25 
26 static char ppbuf[1024];
27 static char console_write_buf[CONSOLE_WRITE_BUF_SIZE];
28 static DEFINE_RAW_SPINLOCK(console_write_lock);
29 
prom_write(const char * buf,unsigned int n)30 void notrace prom_write(const char *buf, unsigned int n)
31 {
32 	unsigned int dest_len;
33 	unsigned long flags;
34 	char *dest;
35 
36 	dest = console_write_buf;
37 	raw_spin_lock_irqsave(&console_write_lock, flags);
38 
39 	dest_len = 0;
40 	while (n-- != 0) {
41 		char ch = *buf++;
42 		if (ch == '\n') {
43 			*dest++ = '\r';
44 			dest_len++;
45 		}
46 		*dest++ = ch;
47 		dest_len++;
48 		if (dest_len >= CONSOLE_WRITE_BUF_SIZE - 1) {
49 			prom_console_write_buf(console_write_buf, dest_len);
50 			dest = console_write_buf;
51 			dest_len = 0;
52 		}
53 	}
54 	if (dest_len)
55 		prom_console_write_buf(console_write_buf, dest_len);
56 
57 	raw_spin_unlock_irqrestore(&console_write_lock, flags);
58 }
59 
prom_printf(const char * fmt,...)60 void notrace prom_printf(const char *fmt, ...)
61 {
62 	va_list args;
63 	int i;
64 
65 	va_start(args, fmt);
66 	i = vscnprintf(ppbuf, sizeof(ppbuf), fmt, args);
67 	va_end(args);
68 
69 	prom_write(ppbuf, i);
70 }
71