[apple/xnu.git] / osfmk / console / ppc / serial_console.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/*
 * @APPLE_FREE_COPYRIGHT@
 */

#include <mach_kdb.h>
#include <platforms.h>
#include <serial_console_default.h>

#include <kern/spl.h>
#include <machine/machparam.h>		/* spl definitions */
#include <types.h>
#include <console/video_console.h>
#include <ppc/misc_protos.h>
#include <ppc/serial_io.h>
#include <kern/cpu_number.h>
#include <ppc/Firmware.h>
#include <ppc/proc_reg.h>
#include <pexpert/pexpert.h>

/*
 * A machine MUST have a console.  In our case
 * things are a little complicated by the graphic
 * display: people expect it to be their "console",
 * but we'd like to be able to live without it.
 * This is not to be confused with the "rconsole" thing:
 * that just duplicates the console I/O to
 * another place (for debugging/logging purposes).
 */

const int console_unit = 0;
const int console_chan_default = CONSOLE_PORT;
#define console_chan (console_chan_default) /* ^ cpu_number()) */

#define OPS(putc, getc, nosplputc, nosplgetc) putc, getc

const struct console_ops {
	int	(*putc)(int, int, int);
	int	(*getc)(int, int, boolean_t, boolean_t);
} cons_ops[] = {
#define SCC_CONS_OPS 0
	{OPS(scc_putc, scc_getc, no_spl_scputc, no_spl_scgetc)},
#define VC_CONS_OPS 1
	{OPS(vcputc, vcgetc, no_spl_vcputc, no_spl_vcgetc)},
};
#define NCONSOPS (sizeof cons_ops / sizeof cons_ops[0])

#if SERIAL_CONSOLE_DEFAULT
#define CONS_OPS SCC_CONS_OPS
#define CONS_NAME "com"
#else
#define CONS_OPS VC_CONS_OPS
#define CONS_NAME "vc"
#endif

#define MP_SAFE_CONSOLE 1	/* Set this to 1 to allow more than 1 processor to print at once */
#if MP_SAFE_CONSOLE

struct ppcbfr {													/* Controls multiple processor output */
	unsigned int 	pos;										/* Current position in buffer */
	unsigned int	noprompt;									/* Set if we skip the prompt */
	unsigned int	echo;										/* Control character echoing */
	char			buffer[256];								/* Fairly big buffer */	
};
typedef struct ppcbfr ppcbfr;
ppcbfr cbfr[NCPUS];												/* Get one of these for each processor */
volatile unsigned int cbfpend;									/* A buffer is pending output */
volatile unsigned int sconowner=-1;								/* Mark who's actually writing */

#endif


unsigned int cons_ops_index = CONS_OPS;
unsigned int killprint = 0;
unsigned int debcnputc = 0;
extern unsigned int	mappingdeb0;
extern int debugger_holdoff[NCPUS];
extern int debugger_cpu;

static void _cnputc(char c)
{
	cons_ops[cons_ops_index].putc(console_unit, console_chan, c);
}

void cnputcusr(char c) {										/* Echo input character directly */

	unsigned int cpu;
	
	cpu = cpu_number();
	
	hw_atomic_add(&debugger_holdoff[cpu], 1);					/* Don't allow debugger entry just now (this is a HACK) */
	
	_cnputc( c);												/* Echo the character */
	if(c=='\n') _cnputc( '\r');									/* Add a return if we had a new line */
	
	hw_atomic_sub(&debugger_holdoff[cpu], 1);					/* Don't allow debugger entry just now (this is a HACK) */
	return;
}

void
cnputc(char c)
{

	unsigned int oldpend, i, cpu, ourbit, sccpu;
	spl_t 		s;
		
#if MP_SAFE_CONSOLE

/*
 *		Handle multiple CPU console output.
 *		Note: this thing has gotten god-awful complicated.  We need a better way.
 */
 	

	if(killprint) {		
		return;													/* If printing is disabled, bail... */
	}	
	
	cpu = cpu_number();

	hw_atomic_add(&debugger_holdoff[cpu], 1);					/* Don't allow debugger entry just now (this is a HACK) */

	ourbit = 1 << cpu;											/* Make a mask for just us */
	if(debugger_cpu != -1) {									/* Are we in the debugger with empty buffers? */
	
		while(sconowner != cpu) {								/* Anyone but us? */
			hw_compare_and_store(-1, cpu, (unsigned int *)&sconowner);	/* Try to mark it for us if idle */
		}
	
		_cnputc( c);											/* Yeah, just write it */
		if(c=='\n')												/* Did we just write a new line? */
			_cnputc( '\r');										/* Yeah, just add a return */
			
		sconowner=-1;											/* Mark it idle */	
		hw_atomic_sub(&debugger_holdoff[cpu], 1);				/* Don't allow debugger entry just now (this is a HACK) */
		
		return;													/* Leave... */
	}

	s=splhigh();												/* Don't bother me */
	
	while(ourbit&cbfpend);										/* We aren't "double buffered," so we'll just wait until the buffers are written */
	isync();													/* Just in case we had to wait */
	
	if(c) {														/* If the character is not null */
		cbfr[cpu].buffer[cbfr[cpu].pos]=c;						/* Fill in the buffer for our CPU */
		cbfr[cpu].pos++;										/* Up the count */
		if(cbfr[cpu].pos > 253) {								/* Is the buffer full? */
			cbfr[cpu].buffer[254]='\n';							/* Yeah, set the second to last as a LF */
			cbfr[cpu].buffer[255]='\r';							/* And the last to a CR */
			cbfr[cpu].pos=256;									/* Push the buffer to the end */
			c='\r';												/* Set character to a CR */
		}
	}
	
	if(c == '\n') {												/* Are we finishing a line? */
		cbfr[cpu].buffer[cbfr[cpu].pos]='\r';					/* And the last to a CR */
		cbfr[cpu].pos++;										/* Up the count */
		c='\r';													/* Set character to a CR */
	}

#if 1
	if(cbfr[cpu].echo == 1) {									/* Did we hit an escape last time? */
		if(c == 'K') {											/* Is it a partial clear? */
			cbfr[cpu].echo = 2;									/* Yes, enter echo mode */
		}
		else cbfr[cpu].echo = 0;								/* Otherwise reset escape */
	}
	else if(cbfr[cpu].echo == 0) {								/* Not in escape sequence, see if we should enter */
		cbfr[cpu].echo = 1;										/* Set that we are in escape sequence */
	}
#endif

	if((c == 0x00) || (c == '\r') || (cbfr[cpu].echo == 2)) {	/* Try to push out all buffers if we see CR or null */
				
		while(1) {												/* Loop until we see who's doing this */
			oldpend=cbfpend;									/* Get the currentest pending buffer flags */
			if(hw_compare_and_store(oldpend, oldpend|ourbit, (unsigned int *)&cbfpend))	/* Swap ours on if no change */
				break;											/* Bail the loop if it worked */
		}
		
		if(!hw_compare_and_store(-1, cpu, (unsigned int *)&sconowner)) {	/* See if someone else has this, and take it if not */
			debugger_holdoff[cpu] = 0;							/* Allow debugger entry (this is a HACK) */
			splx(s);											/* Let's take some 'rupts now */
			return;												/* We leave here, 'cause another processor is already writing the buffers */
		}
				
		while(1) {												/* Loop to dump out all of the finished buffers */
			oldpend=cbfpend;									/* Get the most current finished buffers */
			for(sccpu=0; sccpu<NCPUS; sccpu++) {				/* Cycle through all CPUs buffers */
				
				if(oldpend&(1<<sccpu)) {						/* Does this guy have a buffer to do? */

#if 0
					if(!cbfr[sccpu].noprompt) {					/* Don't prompt if there was not CR before */
						_cnputc( '{');	/* Mark CPU number */
						_cnputc( '0'+sccpu);	/* Mark CPU number */
						_cnputc( '.');	/* (TEST/DEBUG) */
						_cnputc( '0'+cpu);	/* (TEST/DEBUG) */
						_cnputc( '}');	/* Mark CPU number */
						_cnputc( ' ');	/* Mark CPU number */
					}
#endif
					
					for(i=0; i<cbfr[sccpu].pos; i++) {			/* Do the whole buffer */
						_cnputc( cbfr[sccpu].buffer[i]); /* Write it */
					}
					
					if(cbfr[sccpu].buffer[cbfr[sccpu].pos-1]!='\r') {	/* Was the last character a return? */
						cbfr[sccpu].noprompt = 1;				/* Remember not to prompt */
					}
					else {										/* Last was a return */
						cbfr[sccpu].noprompt = 0;				/* Otherwise remember to prompt */
						cbfr[sccpu].echo = 0;					/* And clear echo */
					}
						
					cbfr[sccpu].pos=0;							/* Reset the buffer pointer */
		
					while(!hw_compare_and_store(cbfpend, cbfpend&~(1<<sccpu), (unsigned int *)&cbfpend));	/* Swap it off */
				}
			}
			sconowner=-1;										/* Set the writer to idle */
			sync();												/* Insure that everything's done */
			if(hw_compare_and_store(0, 0, (unsigned int *)&cbfpend)) break;	/* If there are no new buffers, we are done... */
			if(!hw_compare_and_store(-1, cpu, (unsigned int *)&sconowner)) break;	/* If this isn't idle anymore, we're done */
	
		}
	}
	hw_atomic_sub(&debugger_holdoff[cpu], 1);					/* Don't allow debugger entry just now (this is a HACK) */
	splx(s);													/* Let's take some 'rupts now */

#else  /* MP_SAFE_CONSOLE */
	_cnputc( c);
	if (c == '\n')
		_cnputc('\r');
#endif  /* MP_SAFE_CONSOLE */

}

int
cngetc()
{
	return cons_ops[cons_ops_index].getc(console_unit, console_chan,
					     TRUE, FALSE);
}

int
cnmaygetc()
{
	return cons_ops[cons_ops_index].getc(console_unit, console_chan,
					     FALSE, FALSE);
}

boolean_t console_is_serial()
{
	return cons_ops_index == SCC_CONS_OPS;
}

int
switch_to_video_console()
{
	int old_cons_ops = cons_ops_index;
	cons_ops_index = VC_CONS_OPS;
	return old_cons_ops;
}

int
switch_to_serial_console()
{
	int old_cons_ops = cons_ops_index;
	cons_ops_index = SCC_CONS_OPS;
	return old_cons_ops;
}

/* The switch_to_{video,serial,kgdb}_console functions return a cookie that
   can be used to restore the console to whatever it was before, in the
   same way that splwhatever() and splx() work.  */
void
switch_to_old_console(int old_console)
{
	static boolean_t squawked;
	unsigned int ops = old_console;

	if (ops >= NCONSOPS && !squawked) {
		squawked = TRUE;
		printf("switch_to_old_console: unknown ops %d\n", ops);
	} else
		cons_ops_index = ops;
}


int
vcgetc(int l, int u, boolean_t wait, boolean_t raw)
{
	char c;

	if( 0 == (*PE_poll_input)( 0, &c))
		return( c);
	else
		return( 0);
}
Commit	Line	Data
1c79356b A	1	/*
	2	* Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
e5568f75 A	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
1c79356b	11	*
e5568f75 A	12	* This Original Code and all software distributed under the License are
e5568f75 A	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
1c79356b A	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
1c79356b A	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
e5568f75 A	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
1c79356b A	19	*
	20	* @APPLE_LICENSE_HEADER_END@
	21	*/
	22	/*
	23	* @OSF_COPYRIGHT@
	24	*/
	25	/*
	26	* @APPLE_FREE_COPYRIGHT@
	27	*/
	28
	29	#include <mach_kdb.h>
	30	#include <platforms.h>
	31	#include <serial_console_default.h>
	32
	33	#include <kern/spl.h>
	34	#include <machine/machparam.h> /* spl definitions */
	35	#include <types.h>
55e303ae	36	#include <console/video_console.h>
1c79356b	37	#include <ppc/misc_protos.h>
55e303ae	38	#include <ppc/serial_io.h>
1c79356b A	39	#include <kern/cpu_number.h>
	40	#include <ppc/Firmware.h>
	41	#include <ppc/proc_reg.h>
	42	#include <pexpert/pexpert.h>
	43
	44	/*
	45	* A machine MUST have a console. In our case
	46	* things are a little complicated by the graphic
	47	* display: people expect it to be their "console",
	48	* but we'd like to be able to live without it.
	49	* This is not to be confused with the "rconsole" thing:
	50	* that just duplicates the console I/O to
	51	* another place (for debugging/logging purposes).
	52	*/
	53
	54	const int console_unit = 0;
	55	const int console_chan_default = CONSOLE_PORT;
	56	#define console_chan (console_chan_default) /* ^ cpu_number()) */
	57
	58	#define OPS(putc, getc, nosplputc, nosplgetc) putc, getc
	59
	60	const struct console_ops {
	61	int (*putc)(int, int, int);
	62	int (*getc)(int, int, boolean_t, boolean_t);
	63	} cons_ops[] = {
	64	#define SCC_CONS_OPS 0
	65	{OPS(scc_putc, scc_getc, no_spl_scputc, no_spl_scgetc)},
	66	#define VC_CONS_OPS 1
	67	{OPS(vcputc, vcgetc, no_spl_vcputc, no_spl_vcgetc)},
	68	};
	69	#define NCONSOPS (sizeof cons_ops / sizeof cons_ops[0])
	70
	71	#if SERIAL_CONSOLE_DEFAULT
	72	#define CONS_OPS SCC_CONS_OPS
	73	#define CONS_NAME "com"
	74	#else
	75	#define CONS_OPS VC_CONS_OPS
	76	#define CONS_NAME "vc"
	77	#endif
	78
	79	#define MP_SAFE_CONSOLE 1 /* Set this to 1 to allow more than 1 processor to print at once */
	80	#if MP_SAFE_CONSOLE
	81
	82	struct ppcbfr { /* Controls multiple processor output */
	83	unsigned int pos; /* Current position in buffer */
	84	unsigned int noprompt; /* Set if we skip the prompt */
	85	unsigned int echo; /* Control character echoing */
	86	char buffer[256]; /* Fairly big buffer */
	87	};
	88	typedef struct ppcbfr ppcbfr;
	89	ppcbfr cbfr[NCPUS]; /* Get one of these for each processor */
	90	volatile unsigned int cbfpend; /* A buffer is pending output */
	91	volatile unsigned int sconowner=-1; /* Mark who's actually writing */
	92
	93	#endif
	94
	95
	96	unsigned int cons_ops_index = CONS_OPS;
	97	unsigned int killprint = 0;
	98	unsigned int debcnputc = 0;
	99	extern unsigned int mappingdeb0;
	100	extern int debugger_holdoff[NCPUS];
55e303ae	101	extern int debugger_cpu;
1c79356b A	102
	103	static void _cnputc(char c)
	104	{
	105	cons_ops[cons_ops_index].putc(console_unit, console_chan, c);
	106	}
	107
	108	void cnputcusr(char c) { /* Echo input character directly */
	109
	110	unsigned int cpu;
	111
9bccf70c	112	cpu = cpu_number();
1c79356b A	113
	114	hw_atomic_add(&debugger_holdoff[cpu], 1); /* Don't allow debugger entry just now (this is a HACK) */
	115
	116	_cnputc( c); /* Echo the character */
	117	if(c=='\n') _cnputc( '\r'); /* Add a return if we had a new line */
	118
	119	hw_atomic_sub(&debugger_holdoff[cpu], 1); /* Don't allow debugger entry just now (this is a HACK) */
	120	return;
	121	}
	122
	123	void
	124	cnputc(char c)
	125	{
	126
	127	unsigned int oldpend, i, cpu, ourbit, sccpu;
	128	spl_t s;
	129
	130	#if MP_SAFE_CONSOLE
	131
	132	/*
	133	* Handle multiple CPU console output.
	134	* Note: this thing has gotten god-awful complicated. We need a better way.
	135	*/
	136
	137
	138	if(killprint) {
	139	return; /* If printing is disabled, bail... */
	140	}
	141
9bccf70c	142	cpu = cpu_number();
1c79356b A	143
	144	hw_atomic_add(&debugger_holdoff[cpu], 1); /* Don't allow debugger entry just now (this is a HACK) */
	145
	146	ourbit = 1 << cpu; /* Make a mask for just us */
	147	if(debugger_cpu != -1) { /* Are we in the debugger with empty buffers? */
	148
	149	while(sconowner != cpu) { /* Anyone but us? */
	150	hw_compare_and_store(-1, cpu, (unsigned int )&sconowner); / Try to mark it for us if idle */
	151	}
	152
	153	_cnputc( c); /* Yeah, just write it */
	154	if(c=='\n') /* Did we just write a new line? */
	155	_cnputc( '\r'); /* Yeah, just add a return */
	156
	157	sconowner=-1; /* Mark it idle */
	158	hw_atomic_sub(&debugger_holdoff[cpu], 1); /* Don't allow debugger entry just now (this is a HACK) */
	159
	160	return; /* Leave... */
	161	}
	162
	163	s=splhigh(); /* Don't bother me */
	164
	165	while(ourbit&cbfpend); /* We aren't "double buffered," so we'll just wait until the buffers are written */
	166	isync(); /* Just in case we had to wait */
	167
	168	if(c) { /* If the character is not null */
	169	cbfr[cpu].buffer[cbfr[cpu].pos]=c; /* Fill in the buffer for our CPU */
	170	cbfr[cpu].pos++; /* Up the count */
	171	if(cbfr[cpu].pos > 253) { /* Is the buffer full? */
	172	cbfr[cpu].buffer[254]='\n'; /* Yeah, set the second to last as a LF */
	173	cbfr[cpu].buffer[255]='\r'; /* And the last to a CR */
	174	cbfr[cpu].pos=256; /* Push the buffer to the end */
	175	c='\r'; /* Set character to a CR */
	176	}
	177	}
	178
	179	if(c == '\n') { /* Are we finishing a line? */
	180	cbfr[cpu].buffer[cbfr[cpu].pos]='\r'; /* And the last to a CR */
	181	cbfr[cpu].pos++; /* Up the count */
	182	c='\r'; /* Set character to a CR */
	183	}
	184
	185	#if 1
	186	if(cbfr[cpu].echo == 1) { /* Did we hit an escape last time? */
	187	if(c == 'K') { /* Is it a partial clear? */
	188	cbfr[cpu].echo = 2; /* Yes, enter echo mode */
	189	}
	190	else cbfr[cpu].echo = 0; /* Otherwise reset escape */
	191	}
	192	else if(cbfr[cpu].echo == 0) { /* Not in escape sequence, see if we should enter */
	193	cbfr[cpu].echo = 1; /* Set that we are in escape sequence */
	194	}
	195	#endif
	196
	197	if((c == 0x00) \|\| (c == '\r') \|\| (cbfr[cpu].echo == 2)) { /* Try to push out all buffers if we see CR or null */
	198
	199	while(1) { /* Loop until we see who's doing this */
	200	oldpend=cbfpend; /* Get the currentest pending buffer flags */
	201	if(hw_compare_and_store(oldpend, oldpend\|ourbit, (unsigned int )&cbfpend)) / Swap ours on if no change */
	202	break; /* Bail the loop if it worked */
	203	}
	204
	205	if(!hw_compare_and_store(-1, cpu, (unsigned int )&sconowner)) { / See if someone else has this, and take it if not */
	206	debugger_holdoff[cpu] = 0; /* Allow debugger entry (this is a HACK) */
207	splx(s); /* Let's take some 'rupts now */
208	return; /* We leave here, 'cause another processor is already writing the buffers */
209	}
210
211	while(1) { /* Loop to dump out all of the finished buffers */
212	oldpend=cbfpend; /* Get the most current finished buffers */
213	for(sccpu=0; sccpu<NCPUS; sccpu++) { /* Cycle through all CPUs buffers */
214
215	if(oldpend&(1<<sccpu)) { /* Does this guy have a buffer to do? */
216
217	#if 0
218	if(!cbfr[sccpu].noprompt) { /* Don't prompt if there was not CR before */
219	_cnputc( '{'); /* Mark CPU number */
220	_cnputc( '0'+sccpu); /* Mark CPU number */
221	_cnputc( '.'); /* (TEST/DEBUG) */
222	_cnputc( '0'+cpu); /* (TEST/DEBUG) */
223	_cnputc( '}'); /* Mark CPU number */
224	_cnputc( ' '); /* Mark CPU number */
225	}
226	#endif
227
228	for(i=0; i<cbfr[sccpu].pos; i++) { /* Do the whole buffer */
229	_cnputc( cbfr[sccpu].buffer[i]); /* Write it */
230	}
231
232	if(cbfr[sccpu].buffer[cbfr[sccpu].pos-1]!='\r') { /* Was the last character a return? */
233	cbfr[sccpu].noprompt = 1; /* Remember not to prompt */
234	}
235	else { /* Last was a return */
236	cbfr[sccpu].noprompt = 0; /* Otherwise remember to prompt */
237	cbfr[sccpu].echo = 0; /* And clear echo */
238	}
239
240	cbfr[sccpu].pos=0; /* Reset the buffer pointer */
241
242	while(!hw_compare_and_store(cbfpend, cbfpend&~(1<<sccpu), (unsigned int )&cbfpend)); / Swap it off */
243	}
244	}
245	sconowner=-1; /* Set the writer to idle */
246	sync(); /* Insure that everything's done */
247	if(hw_compare_and_store(0, 0, (unsigned int )&cbfpend)) break; / If there are no new buffers, we are done... */
248	if(!hw_compare_and_store(-1, cpu, (unsigned int )&sconowner)) break; / If this isn't idle anymore, we're done */
249
250	}
251	}
252	hw_atomic_sub(&debugger_holdoff[cpu], 1); /* Don't allow debugger entry just now (this is a HACK) */
253	splx(s); /* Let's take some 'rupts now */
254
255	#else /* MP_SAFE_CONSOLE */
256	_cnputc( c);
257	if (c == '\n')
258	_cnputc('\r');
259	#endif /* MP_SAFE_CONSOLE */
260
261	}
262
263	int
264	cngetc()
265	{
266	return cons_ops[cons_ops_index].getc(console_unit, console_chan,
267	TRUE, FALSE);
268	}
269
270	int
271	cnmaygetc()
272	{
273	return cons_ops[cons_ops_index].getc(console_unit, console_chan,
274	FALSE, FALSE);
275	}
276
277	boolean_t console_is_serial()
278	{
279	return cons_ops_index == SCC_CONS_OPS;
280	}
281
282	int
283	switch_to_video_console()
284	{
285	int old_cons_ops = cons_ops_index;
286	cons_ops_index = VC_CONS_OPS;
287	return old_cons_ops;
288	}
289
290	int
291	switch_to_serial_console()
292	{
293	int old_cons_ops = cons_ops_index;
294	cons_ops_index = SCC_CONS_OPS;
295	return old_cons_ops;
296	}
297
298	/* The switch_to_{video,serial,kgdb}_console functions return a cookie that
299	can be used to restore the console to whatever it was before, in the
300	same way that splwhatever() and splx() work. */
301	void
302	switch_to_old_console(int old_console)
303	{
304	static boolean_t squawked;
305	unsigned int ops = old_console;
306
307	if (ops >= NCONSOPS && !squawked) {
308	squawked = TRUE;
309	printf("switch_to_old_console: unknown ops %d\n", ops);
310	} else
311	cons_ops_index = ops;
312	}
313
314
315	int
316	vcgetc(int l, int u, boolean_t wait, boolean_t raw)
317	{
318	char c;
319
320	if( 0 == (*PE_poll_input)( 0, &c))
321	return( c);
322	else
323	return( 0);
324	}