xref: /freebsd/sys/i386/i386/bios.c (revision e796cc77c586c2955b2f3940dbf4991b31e8d289)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 1997 Michael Smith
5  * Copyright (c) 1998 Jonathan Lemon
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
32 
33 /*
34  * Code for dealing with the BIOS in x86 PC systems.
35  */
36 
37 #include "opt_isa.h"
38 
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/kernel.h>
42 #include <sys/malloc.h>
43 #include <sys/module.h>
44 #include <sys/bus.h>
45 #include <sys/pcpu.h>
46 #include <vm/vm.h>
47 #include <vm/pmap.h>
48 #include <machine/md_var.h>
49 #include <machine/segments.h>
50 #include <machine/stdarg.h>
51 #include <machine/vmparam.h>
52 #include <machine/pc/bios.h>
53 #ifdef DEV_ISA
54 #include <isa/isavar.h>
55 #include <isa/pnpreg.h>
56 #include <isa/pnpvar.h>
57 #endif
58 
59 #define BIOS_START	0xe0000
60 #define BIOS_SIZE	0x20000
61 
62 /* exported lookup results */
63 struct bios32_SDentry		PCIbios;
64 
65 static struct PnPBIOS_table	*PnPBIOStable;
66 
67 static u_int			bios32_SDCI;
68 
69 /* start fairly early */
70 static void			bios32_init(void *junk);
71 SYSINIT(bios32, SI_SUB_CPU, SI_ORDER_ANY, bios32_init, NULL);
72 
73 /*
74  * bios32_init
75  *
76  * Locate various bios32 entities.
77  */
78 static void
79 bios32_init(void *junk)
80 {
81     u_long			sigaddr;
82     struct bios32_SDheader	*sdh;
83     struct PnPBIOS_table	*pt;
84     u_int8_t			ck, *cv;
85     int				i;
86     char			*p;
87 
88     /*
89      * BIOS32 Service Directory, PCI BIOS
90      */
91 
92     /* look for the signature */
93     if ((sigaddr = bios_sigsearch(0, "_32_", 4, 16, 0)) != 0) {
94 
95 	/* get a virtual pointer to the structure */
96 	sdh = (struct bios32_SDheader *)(uintptr_t)BIOS_PADDRTOVADDR(sigaddr);
97 	for (cv = (u_int8_t *)sdh, ck = 0, i = 0; i < (sdh->len * 16); i++) {
98 	    ck += cv[i];
99 	}
100 	/* If checksum is OK, enable use of the entrypoint */
101 	if ((ck == 0) && (BIOS_START <= sdh->entry ) &&
102 	    (sdh->entry < (BIOS_START + BIOS_SIZE))) {
103 	    bios32_SDCI = BIOS_PADDRTOVADDR(sdh->entry);
104 	    if (bootverbose) {
105 		printf("bios32: Found BIOS32 Service Directory header at %p\n", sdh);
106 		printf("bios32: Entry = 0x%x (%x)  Rev = %d  Len = %d\n",
107 		       sdh->entry, bios32_SDCI, sdh->revision, sdh->len);
108 	    }
109 
110 	    /* Allow user override of PCI BIOS search */
111 	    if (((p = kern_getenv("machdep.bios.pci")) == NULL) || strcmp(p, "disable")) {
112 
113 		/* See if there's a PCI BIOS entrypoint here */
114 		PCIbios.ident.id = 0x49435024;	/* PCI systems should have this */
115 		if (!bios32_SDlookup(&PCIbios) && bootverbose)
116 		    printf("pcibios: PCI BIOS entry at 0x%x+0x%x\n", PCIbios.base, PCIbios.entry);
117 	    }
118 	    if (p != NULL)
119 		    freeenv(p);
120 	} else {
121 	    printf("bios32: Bad BIOS32 Service Directory\n");
122 	}
123     }
124 
125     /*
126      * PnP BIOS
127      *
128      * Allow user override of PnP BIOS search
129      */
130     if ((((p = kern_getenv("machdep.bios.pnp")) == NULL) || strcmp(p, "disable")) &&
131 	((sigaddr = bios_sigsearch(0, "$PnP", 4, 16, 0)) != 0)) {
132 
133 	/* get a virtual pointer to the structure */
134 	pt = (struct PnPBIOS_table *)(uintptr_t)BIOS_PADDRTOVADDR(sigaddr);
135 	for (cv = (u_int8_t *)pt, ck = 0, i = 0; i < pt->len; i++) {
136 	    ck += cv[i];
137 	}
138 	/* If checksum is OK, enable use of the entrypoint */
139 	if (ck == 0) {
140 	    PnPBIOStable = pt;
141 	    if (bootverbose) {
142 		printf("pnpbios: Found PnP BIOS data at %p\n", pt);
143 		printf("pnpbios: Entry = %x:%x  Rev = %d.%d\n",
144 		       pt->pmentrybase, pt->pmentryoffset, pt->version >> 4, pt->version & 0xf);
145 		if ((pt->control & 0x3) == 0x01)
146 		    printf("pnpbios: Event flag at %x\n", pt->evflagaddr);
147 		if (pt->oemdevid != 0)
148 		    printf("pnpbios: OEM ID %x\n", pt->oemdevid);
149 
150 	    }
151 	} else {
152 	    printf("pnpbios: Bad PnP BIOS data checksum\n");
153 	}
154     }
155     if (p != NULL)
156 	    freeenv(p);
157     if (bootverbose) {
158 	    /* look for other know signatures */
159 	    printf("Other BIOS signatures found:\n");
160     }
161 }
162 
163 /*
164  * bios32_SDlookup
165  *
166  * Query the BIOS32 Service Directory for the service named in (ent),
167  * returns nonzero if the lookup fails.  The caller must fill in
168  * (ent->ident), the remainder are populated on a successful lookup.
169  */
170 int
171 bios32_SDlookup(struct bios32_SDentry *ent)
172 {
173     struct bios_regs args;
174 
175     if (bios32_SDCI == 0)
176 	return (1);
177 
178     args.eax = ent->ident.id;		/* set up arguments */
179     args.ebx = args.ecx = args.edx = 0;
180     bios32(&args, bios32_SDCI, GSEL(GCODE_SEL, SEL_KPL));
181     if ((args.eax & 0xff) == 0) {	/* success? */
182 	ent->base = args.ebx;
183 	ent->len = args.ecx;
184 	ent->entry = args.edx;
185 	ent->ventry = BIOS_PADDRTOVADDR(ent->base + ent->entry);
186 	return (0);			/* all OK */
187     }
188     return (1);				/* failed */
189 }
190 
191 
192 /*
193  * bios_sigsearch
194  *
195  * Search some or all of the BIOS region for a signature string.
196  *
197  * (start)	Optional offset returned from this function
198  *		(for searching for multiple matches), or NULL
199  *		to start the search from the base of the BIOS.
200  *		Note that this will be a _physical_ address in
201  *		the range 0xe0000 - 0xfffff.
202  * (sig)	is a pointer to the byte(s) of the signature.
203  * (siglen)	number of bytes in the signature.
204  * (paralen)	signature paragraph (alignment) size.
205  * (sigofs)	offset of the signature within the paragraph.
206  *
207  * Returns the _physical_ address of the found signature, 0 if the
208  * signature was not found.
209  */
210 
211 u_int32_t
212 bios_sigsearch(u_int32_t start, u_char *sig, int siglen, int paralen, int sigofs)
213 {
214     u_char	*sp, *end;
215 
216     /* compute the starting address */
217     if ((start >= BIOS_START) && (start <= (BIOS_START + BIOS_SIZE))) {
218 	sp = (char *)BIOS_PADDRTOVADDR(start);
219     } else if (start == 0) {
220 	sp = (char *)BIOS_PADDRTOVADDR(BIOS_START);
221     } else {
222 	return 0;				/* bogus start address */
223     }
224 
225     /* compute the end address */
226     end = (u_char *)BIOS_PADDRTOVADDR(BIOS_START + BIOS_SIZE);
227 
228     /* loop searching */
229     while ((sp + sigofs + siglen) < end) {
230 
231 	/* compare here */
232 	if (!bcmp(sp + sigofs, sig, siglen)) {
233 	    /* convert back to physical address */
234 	    return((u_int32_t)BIOS_VADDRTOPADDR(sp));
235 	}
236 	sp += paralen;
237     }
238     return(0);
239 }
240 
241 /*
242  * do not staticize, used by bioscall.s
243  */
244 union {
245     struct {
246 	u_short	offset;
247 	u_short	segment;
248     } vec16;
249     struct {
250 	u_int	offset;
251 	u_short	segment;
252     } vec32;
253 } bioscall_vector;			/* bios jump vector */
254 
255 void
256 set_bios_selectors(struct bios_segments *seg, int flags)
257 {
258     struct soft_segment_descriptor ssd = {
259 	0,			/* segment base address (overwritten) */
260 	0,			/* length (overwritten) */
261 	SDT_MEMERA,		/* segment type (overwritten) */
262 	0,			/* priority level */
263 	1,			/* descriptor present */
264 	0, 0,
265 	1,			/* descriptor size (overwritten) */
266 	0			/* granularity == byte units */
267     };
268     union descriptor *p_gdt;
269 
270 #ifdef SMP
271     p_gdt = &gdt[PCPU_GET(cpuid) * NGDT];
272 #else
273     p_gdt = gdt;
274 #endif
275 
276     ssd.ssd_base = seg->code32.base;
277     ssd.ssd_limit = seg->code32.limit;
278     ssdtosd(&ssd, &p_gdt[GBIOSCODE32_SEL].sd);
279 
280     ssd.ssd_def32 = 0;
281     if (flags & BIOSCODE_FLAG) {
282 	ssd.ssd_base = seg->code16.base;
283 	ssd.ssd_limit = seg->code16.limit;
284 	ssdtosd(&ssd, &p_gdt[GBIOSCODE16_SEL].sd);
285     }
286 
287     ssd.ssd_type = SDT_MEMRWA;
288     if (flags & BIOSDATA_FLAG) {
289 	ssd.ssd_base = seg->data.base;
290 	ssd.ssd_limit = seg->data.limit;
291 	ssdtosd(&ssd, &p_gdt[GBIOSDATA_SEL].sd);
292     }
293 
294     if (flags & BIOSUTIL_FLAG) {
295 	ssd.ssd_base = seg->util.base;
296 	ssd.ssd_limit = seg->util.limit;
297 	ssdtosd(&ssd, &p_gdt[GBIOSUTIL_SEL].sd);
298     }
299 
300     if (flags & BIOSARGS_FLAG) {
301 	ssd.ssd_base = seg->args.base;
302 	ssd.ssd_limit = seg->args.limit;
303 	ssdtosd(&ssd, &p_gdt[GBIOSARGS_SEL].sd);
304     }
305 }
306 
307 extern int vm86pa;
308 extern void bios16_jmp(void);
309 
310 /*
311  * this routine is really greedy with selectors, and uses 5:
312  *
313  * 32-bit code selector:	to return to kernel
314  * 16-bit code selector:	for running code
315  *        data selector:	for 16-bit data
316  *        util selector:	extra utility selector
317  *        args selector:	to handle pointers
318  *
319  * the util selector is set from the util16 entry in bios16_args, if a
320  * "U" specifier is seen.
321  *
322  * See <machine/pc/bios.h> for description of format specifiers
323  */
324 int
325 bios16(struct bios_args *args, char *fmt, ...)
326 {
327     char	*p, *stack, *stack_top;
328     va_list 	ap;
329     int 	flags = BIOSCODE_FLAG | BIOSDATA_FLAG;
330     u_int 	i, arg_start, arg_end;
331     pt_entry_t	*pte;
332     pd_entry_t	*ptd;
333 
334     arg_start = 0xffffffff;
335     arg_end = 0;
336 
337     /*
338      * Some BIOS entrypoints attempt to copy the largest-case
339      * argument frame (in order to generalise handling for
340      * different entry types).  If our argument frame is
341      * smaller than this, the BIOS will reach off the top of
342      * our constructed stack segment.  Pad the top of the stack
343      * with some garbage to avoid this.
344      */
345     stack = (caddr_t)PAGE_SIZE - 32;
346 
347     va_start(ap, fmt);
348     for (p = fmt; p && *p; p++) {
349 	switch (*p) {
350 	case 'p':			/* 32-bit pointer */
351 	    i = va_arg(ap, u_int);
352 	    arg_start = min(arg_start, i);
353 	    arg_end = max(arg_end, i);
354 	    flags |= BIOSARGS_FLAG;
355 	    stack -= 4;
356 	    break;
357 
358 	case 'i':			/* 32-bit integer */
359 	    i = va_arg(ap, u_int);
360 	    stack -= 4;
361 	    break;
362 
363 	case 'U':			/* 16-bit selector */
364 	    flags |= BIOSUTIL_FLAG;
365 	    /* FALLTHROUGH */
366 	case 'D':			/* 16-bit selector */
367 	case 'C':			/* 16-bit selector */
368 	    stack -= 2;
369 	    break;
370 
371 	case 's':			/* 16-bit integer passed as an int */
372 	    i = va_arg(ap, int);
373 	    stack -= 2;
374 	    break;
375 
376 	default:
377 	    va_end(ap);
378 	    return (EINVAL);
379 	}
380     }
381     va_end(ap);
382 
383     if (flags & BIOSARGS_FLAG) {
384 	if (arg_end - arg_start > ctob(16))
385 	    return (EACCES);
386 	args->seg.args.base = arg_start;
387 	args->seg.args.limit = 0xffff;
388     }
389 
390     args->seg.code32.base = (u_int)&bios16_jmp & PG_FRAME;
391     args->seg.code32.limit = 0xffff;
392 
393     ptd = (pd_entry_t *)rcr3();
394 #if defined(PAE) || defined(PAE_TABLES)
395     if (ptd == IdlePDPT)
396 #else
397     if (ptd == IdlePTD)
398 #endif
399     {
400 	/*
401 	 * no page table, so create one and install it.
402 	 */
403 	pte = (pt_entry_t *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK);
404 	ptd = (pd_entry_t *)((u_int)IdlePTD + KERNBASE);
405 	*pte = (vm86pa - PAGE_SIZE) | PG_RW | PG_V;
406 	*ptd = vtophys(pte) | PG_RW | PG_V;
407     } else {
408 	/*
409 	 * this is a user-level page table
410 	 */
411 	pte = PTmap;
412 	*pte = (vm86pa - PAGE_SIZE) | PG_RW | PG_V;
413     }
414     pmap_invalidate_all(kernel_pmap);	/* XXX insurance for now */
415 
416     stack_top = stack;
417     va_start(ap, fmt);
418     for (p = fmt; p && *p; p++) {
419 	switch (*p) {
420 	case 'p':			/* 32-bit pointer */
421 	    i = va_arg(ap, u_int);
422 	    *(u_int *)stack = (i - arg_start) |
423 		(GSEL(GBIOSARGS_SEL, SEL_KPL) << 16);
424 	    stack += 4;
425 	    break;
426 
427 	case 'i':			/* 32-bit integer */
428 	    i = va_arg(ap, u_int);
429 	    *(u_int *)stack = i;
430 	    stack += 4;
431 	    break;
432 
433 	case 'U':			/* 16-bit selector */
434 	    *(u_short *)stack = GSEL(GBIOSUTIL_SEL, SEL_KPL);
435 	    stack += 2;
436 	    break;
437 
438 	case 'D':			/* 16-bit selector */
439 	    *(u_short *)stack = GSEL(GBIOSDATA_SEL, SEL_KPL);
440 	    stack += 2;
441 	    break;
442 
443 	case 'C':			/* 16-bit selector */
444 	    *(u_short *)stack = GSEL(GBIOSCODE16_SEL, SEL_KPL);
445 	    stack += 2;
446 	    break;
447 
448 	case 's':			/* 16-bit integer passed as an int */
449 	    i = va_arg(ap, int);
450 	    *(u_short *)stack = i;
451 	    stack += 2;
452 	    break;
453 
454 	default:
455 	    va_end(ap);
456 	    return (EINVAL);
457 	}
458     }
459     va_end(ap);
460 
461     set_bios_selectors(&args->seg, flags);
462     bioscall_vector.vec16.offset = (u_short)args->entry;
463     bioscall_vector.vec16.segment = GSEL(GBIOSCODE16_SEL, SEL_KPL);
464 
465     i = bios16_call(&args->r, stack_top);
466 
467     if (pte == PTmap) {
468 	*pte = 0;			/* remove entry */
469 	/*
470 	 * XXX only needs to be invlpg(0) but that doesn't work on the 386
471 	 */
472 	pmap_invalidate_all(kernel_pmap);
473     } else {
474 	*ptd = 0;			/* remove page table */
475 	/*
476 	 * XXX only needs to be invlpg(0) but that doesn't work on the 386
477 	 */
478 	pmap_invalidate_all(kernel_pmap);
479 	free(pte, M_TEMP);		/* ... and free it */
480     }
481     return (i);
482 }
483 
484 int
485 bios_oem_strings(struct bios_oem *oem, u_char *buffer, size_t maxlen)
486 {
487 	size_t idx = 0;
488 	struct bios_oem_signature *sig;
489 	u_int from, to;
490 	u_char c, *s, *se, *str, *bios_str;
491 	size_t i, off, len, tot;
492 
493 	if ( !oem || !buffer || maxlen<2 )
494 		return(-1);
495 
496 	sig = oem->signature;
497 	if (!sig)
498 		return(-2);
499 
500 	from = oem->range.from;
501 	to = oem->range.to;
502 	if ( (to<=from) || (from<BIOS_START) || (to>(BIOS_START+BIOS_SIZE)) )
503 		return(-3);
504 
505 	while (sig->anchor != NULL) {
506 		str = sig->anchor;
507 		len = strlen(str);
508 		off = sig->offset;
509 		tot = sig->totlen;
510 		/* make sure offset doesn't go beyond bios area */
511 		if ( (to+off)>(BIOS_START+BIOS_SIZE) ||
512 					((from+off)<BIOS_START) ) {
513 			printf("sys/i386/i386/bios.c: sig '%s' "
514 				"from 0x%0x to 0x%0x offset %d "
515 				"out of BIOS bounds 0x%0x - 0x%0x\n",
516 				str, from, to, off,
517 				BIOS_START, BIOS_START+BIOS_SIZE);
518 			return(-4);
519 		}
520 		/* make sure we don't overrun return buffer */
521 		if (idx + tot > maxlen - 1) {
522 			printf("sys/i386/i386/bios.c: sig '%s' "
523 				"idx %d + tot %d = %d > maxlen-1 %d\n",
524 				str, idx, tot, idx+tot, maxlen-1);
525 			return(-5);
526 		}
527 		bios_str = NULL;
528 		s = (u_char *)BIOS_PADDRTOVADDR(from);
529 		se = (u_char *)BIOS_PADDRTOVADDR(to-len);
530 		for (; s<se; s++) {
531 			if (!bcmp(str, s, len)) {
532 				bios_str = s;
533 				break;
534 			}
535 		}
536 		/*
537 		*  store pretty version of totlen bytes of bios string with
538 		*  given offset; 0x20 - 0x7E are printable; uniquify spaces
539 		*/
540 		if (bios_str) {
541 			for (i=0; i<tot; i++) {
542 				c = bios_str[i+off];
543 				if ( (c < 0x20) || (c > 0x7E) )
544 					c = ' ';
545 				if (idx == 0) {
546 					if (c != ' ')
547 						buffer[idx++] = c;
548 				} else if ( (c != ' ') ||
549 					((c == ' ') && (buffer[idx-1] != ' ')) )
550 						buffer[idx++] = c;
551 			}
552 		}
553 		sig++;
554 	}
555 	/* remove a final trailing space */
556 	if ( (idx > 1) && (buffer[idx-1] == ' ') )
557 		idx--;
558 	buffer[idx] = '\0';
559 	return (idx);
560 }
561 
562 #ifdef DEV_ISA
563 /*
564  * PnP BIOS interface; enumerate devices only known to the system
565  * BIOS and save information about them for later use.
566  */
567 
568 struct pnp_sysdev
569 {
570     u_int16_t	size;
571     u_int8_t	handle;
572     u_int32_t	devid;
573     u_int8_t	type[3];
574     u_int16_t	attrib;
575 #define PNPATTR_NODISABLE	(1<<0)	/* can't be disabled */
576 #define PNPATTR_NOCONFIG	(1<<1)	/* can't be configured */
577 #define PNPATTR_OUTPUT		(1<<2)	/* can be primary output */
578 #define PNPATTR_INPUT		(1<<3)	/* can be primary input */
579 #define PNPATTR_BOOTABLE	(1<<4)	/* can be booted from */
580 #define PNPATTR_DOCK		(1<<5)	/* is a docking station */
581 #define PNPATTR_REMOVEABLE	(1<<6)	/* device is removeable */
582 #define PNPATTR_CONFIG_STATIC	(0)
583 #define PNPATTR_CONFIG_DYNAMIC	(1)
584 #define PNPATTR_CONFIG_DYNONLY	(3)
585 #define PNPATTR_CONFIG(a)	(((a) >> 7) & 0x3)
586     /* device-specific data comes here */
587     u_int8_t	devdata[0];
588 } __packed;
589 
590 /* We have to cluster arguments within a 64k range for the bios16 call */
591 struct pnp_sysdevargs
592 {
593     u_int16_t	next;
594     struct pnp_sysdev node;
595 };
596 
597 /*
598  * This function is called after the bus has assigned resource
599  * locations for a logical device.
600  */
601 static void
602 pnpbios_set_config(void *arg, struct isa_config *config, int enable)
603 {
604 }
605 
606 /*
607  * Quiz the PnP BIOS, build a list of PNP IDs and resource data.
608  */
609 static void
610 pnpbios_identify(driver_t *driver, device_t parent)
611 {
612     struct PnPBIOS_table	*pt = PnPBIOStable;
613     struct bios_args		args;
614     struct pnp_sysdev		*pd;
615     struct pnp_sysdevargs	*pda;
616     u_int16_t			ndevs, bigdev;
617     int				error, currdev;
618     u_int8_t			*devnodebuf, tag;
619     u_int32_t			*devid, *compid;
620     int				idx, left;
621     device_t			dev;
622 
623     /* no PnP BIOS information */
624     if (pt == NULL)
625 	return;
626 
627     /* Check to see if ACPI is already active. */
628     dev = devclass_get_device(devclass_find("acpi"), 0);
629     if (dev != NULL && device_is_attached(dev))
630 	return;
631 
632     /* get count of PnP devices */
633     bzero(&args, sizeof(args));
634     args.seg.code16.base = BIOS_PADDRTOVADDR(pt->pmentrybase);
635     args.seg.code16.limit = 0xffff;		/* XXX ? */
636     args.seg.data.base = BIOS_PADDRTOVADDR(pt->pmdataseg);
637     args.seg.data.limit = 0xffff;
638     args.entry = pt->pmentryoffset;
639 
640     if ((error = bios16(&args, PNP_COUNT_DEVNODES, &ndevs, &bigdev)) || (args.r.eax & 0xff)) {
641 	printf("pnpbios: error %d/%x getting device count/size limit\n", error, args.r.eax);
642 	return;
643     }
644     ndevs &= 0xff;				/* clear high byte garbage */
645     if (bootverbose)
646 	printf("pnpbios: %d devices, largest %d bytes\n", ndevs, bigdev);
647 
648     devnodebuf = malloc(bigdev + (sizeof(struct pnp_sysdevargs) - sizeof(struct pnp_sysdev)),
649 			M_DEVBUF, M_NOWAIT);
650     if (devnodebuf == NULL) {
651 	printf("pnpbios: cannot allocate memory, bailing\n");
652 	return;
653     }
654     pda = (struct pnp_sysdevargs *)devnodebuf;
655     pd = &pda->node;
656 
657     for (currdev = 0, left = ndevs; (currdev != 0xff) && (left > 0); left--) {
658 
659 	bzero(pd, bigdev);
660 	pda->next = currdev;
661 	/* get current configuration */
662 	if ((error = bios16(&args, PNP_GET_DEVNODE, &pda->next, &pda->node, 1))) {
663 	    printf("pnpbios: error %d making BIOS16 call\n", error);
664 	    break;
665 	}
666 	if ((error = (args.r.eax & 0xff))) {
667 	    if (bootverbose)
668 		printf("pnpbios: %s 0x%x fetching node %d\n", error & 0x80 ? "error" : "warning", error, currdev);
669 	    if (error & 0x80)
670 		break;
671 	}
672 	currdev = pda->next;
673 	if (pd->size < sizeof(struct pnp_sysdev)) {
674 	    printf("pnpbios: bogus system node data, aborting scan\n");
675 	    break;
676 	}
677 
678 	/*
679 	 * Ignore PICs so that we don't have to worry about the PICs
680 	 * claiming IRQs to prevent their use.  The PIC drivers
681 	 * already ensure that invalid IRQs are not used.
682 	 */
683 	if (!strcmp(pnp_eisaformat(pd->devid), "PNP0000"))	/* ISA PIC */
684 	    continue;
685 	if (!strcmp(pnp_eisaformat(pd->devid), "PNP0003"))	/* APIC */
686 	    continue;
687 
688 	/* Add the device and parse its resources */
689 	dev = BUS_ADD_CHILD(parent, ISA_ORDER_PNPBIOS, NULL, -1);
690 	isa_set_vendorid(dev, pd->devid);
691 	isa_set_logicalid(dev, pd->devid);
692 	/*
693 	 * It appears that some PnP BIOS doesn't allow us to re-enable
694 	 * the embedded system device once it is disabled.  We shall
695 	 * mark all system device nodes as "cannot be disabled", regardless
696 	 * of actual settings in the device attribute byte.
697 	 * XXX
698 	isa_set_configattr(dev,
699 	    ((pd->attrib & PNPATTR_NODISABLE) ?  0 : ISACFGATTR_CANDISABLE) |
700 	    ((!(pd->attrib & PNPATTR_NOCONFIG) &&
701 		PNPATTR_CONFIG(pd->attrib) != PNPATTR_CONFIG_STATIC)
702 		? ISACFGATTR_DYNAMIC : 0));
703 	 */
704 	isa_set_configattr(dev,
705 	    (!(pd->attrib & PNPATTR_NOCONFIG) &&
706 		PNPATTR_CONFIG(pd->attrib) != PNPATTR_CONFIG_STATIC)
707 		? ISACFGATTR_DYNAMIC : 0);
708 	isa_set_pnpbios_handle(dev, pd->handle);
709 	ISA_SET_CONFIG_CALLBACK(parent, dev, pnpbios_set_config, 0);
710 	pnp_parse_resources(dev, &pd->devdata[0],
711 	    pd->size - sizeof(struct pnp_sysdev), 0);
712 	if (!device_get_desc(dev))
713 	    device_set_desc_copy(dev, pnp_eisaformat(pd->devid));
714 
715 	/* Find device IDs */
716 	devid = &pd->devid;
717 	compid = NULL;
718 
719 	/* look for a compatible device ID too */
720 	left = pd->size - sizeof(struct pnp_sysdev);
721 	idx = 0;
722 	while (idx < left) {
723 	    tag = pd->devdata[idx++];
724 	    if (PNP_RES_TYPE(tag) == 0) {
725 		/* Small resource */
726 		switch (PNP_SRES_NUM(tag)) {
727 		case PNP_TAG_COMPAT_DEVICE:
728 		    compid = (u_int32_t *)(pd->devdata + idx);
729 		    if (bootverbose)
730 			printf("pnpbios: node %d compat ID 0x%08x\n", pd->handle, *compid);
731 		    /* FALLTHROUGH */
732 		case PNP_TAG_END:
733 		    idx = left;
734 		    break;
735 		default:
736 		    idx += PNP_SRES_LEN(tag);
737 		    break;
738 		}
739 	    } else
740 		/* Large resource, skip it */
741 		idx += *(u_int16_t *)(pd->devdata + idx) + 2;
742 	}
743 	if (bootverbose) {
744 	    printf("pnpbios: handle %d device ID %s (%08x)",
745 		   pd->handle, pnp_eisaformat(*devid), *devid);
746 	    if (compid != NULL)
747 		printf(" compat ID %s (%08x)",
748 		       pnp_eisaformat(*compid), *compid);
749 	    printf("\n");
750 	}
751     }
752 }
753 
754 static device_method_t pnpbios_methods[] = {
755 	/* Device interface */
756 	DEVMETHOD(device_identify,	pnpbios_identify),
757 
758 	{ 0, 0 }
759 };
760 
761 static driver_t pnpbios_driver = {
762 	"pnpbios",
763 	pnpbios_methods,
764 	1,			/* no softc */
765 };
766 
767 static devclass_t pnpbios_devclass;
768 
769 DRIVER_MODULE(pnpbios, isa, pnpbios_driver, pnpbios_devclass, 0, 0);
770 #endif /* DEV_ISA */
771