devarch.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "io.h"
#include "ureg.h"
#include "../port/error.h"

typedef struct IOMap IOMap;
struct IOMap
{
	IOMap	*next;
	int	reserved;
	char	tag[13];
	ulong	start;
	ulong	end;
};

static struct
{
	Lock;
	IOMap	*m;
	IOMap	*free;
	IOMap	maps[32];		// some initial free maps

	QLock	ql;			// lock for reading map
} iomap;

enum {
	Qdir = 0,
	Qioalloc = 1,
	Qiob,
	Qiow,
	Qiol,
	Qbase,

	Qmax = 16,
};

typedef long Rdwrfn(Chan*, void*, long, vlong);

static Rdwrfn *readfn[Qmax];
static Rdwrfn *writefn[Qmax];

static Dirtab archdir[Qmax] = {
	".",		{ Qdir, 0, QTDIR },	0,	0555,
	"ioalloc",	{ Qioalloc, 0 },	0,	0444,
	"iob",		{ Qiob, 0 },		0,	0660,
	"iow",		{ Qiow, 0 },		0,	0660,
	"iol",		{ Qiol, 0 },		0,	0660,
};
Lock archwlock;	/* the lock is only for changing archdir */
int narchdir = Qbase;
int (*_pcmspecial)(char*, ISAConf*);
void (*_pcmspecialclose)(int);

static int doi8253set = 1;

/*
 * Add a file to the #P listing.  Once added, you can't delete it.
 * You can't add a file with the same name as one already there,
 * and you get a pointer to the Dirtab entry so you can do things
 * like change the Qid version.  Changing the Qid path is disallowed.
 */
Dirtab*
addarchfile(char *name, int perm, Rdwrfn *rdfn, Rdwrfn *wrfn)
{
	int i;
	Dirtab d;
	Dirtab *dp;

	memset(&d, 0, sizeof d);
	strcpy(d.name, name);
	d.perm = perm;

	lock(&archwlock);
	if(narchdir >= Qmax){
		unlock(&archwlock);
		return nil;
	}

	for(i=0; i<narchdir; i++)
		if(strcmp(archdir[i].name, name) == 0){
			unlock(&archwlock);
			return nil;
		}

	d.qid.path = narchdir;
	archdir[narchdir] = d;
	readfn[narchdir] = rdfn;
	writefn[narchdir] = wrfn;
	dp = &archdir[narchdir++];
	unlock(&archwlock);

	return dp;
}

void
ioinit(void)
{
	char *excluded;
	int i;

	for(i = 0; i < nelem(iomap.maps)-1; i++)
		iomap.maps[i].next = &iomap.maps[i+1];
	iomap.maps[i].next = nil;
	iomap.free = iomap.maps;

	/*
	 * This is necessary to make the IBM X20 boot.
	 * Have not tracked down the reason.
	 */
	ioalloc(0x0fff, 1, 0, "dummy");	// i82557 is at 0x1000, the dummy
					// entry is needed for swappable devs.

	if ((excluded = getconf("ioexclude")) != nil) {
		char *s;

		s = excluded;
		while (s && *s != '\0' && *s != '\n') {
			char *ends;
			int io_s, io_e;

			io_s = (int)strtol(s, &ends, 0);
			if (ends == nil || ends == s || *ends != '-') {
				print("ioinit: cannot parse option string\n");
				break;
			}
			s = ++ends;

			io_e = (int)strtol(s, &ends, 0);
			if (ends && *ends == ',')
				*ends++ = '\0';
			s = ends;

			ioalloc(io_s, io_e - io_s + 1, 0, "pre-allocated");
		}
	}

}

// Reserve a range to be ioalloced later. 
// This is in particular useful for exchangable cards, such
// as pcmcia and cardbus cards.
int
ioreserve(int, int size, int align, char *tag)
{
	IOMap *m, **l;
	int i, port;

	lock(&iomap);
	// find a free port above 0x400 and below 0x1000
	port = 0x400;
	for(l = &iomap.m; *l; l = &(*l)->next){
		m = *l;
		if (m->start < 0x400) continue;
		i = m->start - port;
		if(i > size)
			break;
		if(align > 0)
			port = ((port+align-1)/align)*align;
		else
			port = m->end;
	}
	if(*l == nil){
		unlock(&iomap);
		return -1;
	}
	m = iomap.free;
	if(m == nil){
		print("ioalloc: out of maps");
		unlock(&iomap);
		return port;
	}
	iomap.free = m->next;
	m->next = *l;
	m->start = port;
	m->end = port + size;
	m->reserved = 1;
	strncpy(m->tag, tag, sizeof(m->tag));
	m->tag[sizeof(m->tag)-1] = 0;
	*l = m;

	archdir[0].qid.vers++;

	unlock(&iomap);
	return m->start;
}

//
//	alloc some io port space and remember who it was
//	alloced to.  if port < 0, find a free region.
//
int
ioalloc(int port, int size, int align, char *tag)
{
	IOMap *m, **l;
	int i;

	lock(&iomap);
	if(port < 0){
		// find a free port above 0x400 and below 0x1000
		port = 0x400;
		for(l = &iomap.m; *l; l = &(*l)->next){
			m = *l;
			if (m->start < 0x400) continue;
			i = m->start - port;
			if(i > size)
				break;
			if(align > 0)
				port = ((port+align-1)/align)*align;
			else
				port = m->end;
		}
		if(*l == nil){
			unlock(&iomap);
			return -1;
		}
	} else {
		// Only 64KB I/O space on the x86.
		if((port+size) > 0x10000){
			unlock(&iomap);
			return -1;
		}
		// see if the space clashes with previously allocated ports
		for(l = &iomap.m; *l; l = &(*l)->next){
			m = *l;
			if(m->end <= port)
				continue;
			if(m->reserved && m->start == port && m->end == port + size) {
				m->reserved = 0;
				unlock(&iomap);
				return m->start;
			}
			if(m->start >= port+size)
				break;
			unlock(&iomap);
			return -1;
		}
	}
	m = iomap.free;
	if(m == nil){
		print("ioalloc: out of maps");
		unlock(&iomap);
		return port;
	}
	iomap.free = m->next;
	m->next = *l;
	m->start = port;
	m->end = port + size;
	strncpy(m->tag, tag, sizeof(m->tag));
	m->tag[sizeof(m->tag)-1] = 0;
	*l = m;

	archdir[0].qid.vers++;

	unlock(&iomap);
	return m->start;
}

void
iofree(int port)
{
	IOMap *m, **l;

	lock(&iomap);
	for(l = &iomap.m; *l; l = &(*l)->next){
		if((*l)->start == port){
			m = *l;
			*l = m->next;
			m->next = iomap.free;
			iomap.free = m;
			break;
		}
		if((*l)->start > port)
			break;
	}
	archdir[0].qid.vers++;
	unlock(&iomap);
}

int
iounused(int start, int end)
{
	IOMap *m;

	for(m = iomap.m; m; m = m->next){
		if(start >= m->start && start < m->end
		|| start <= m->start && end > m->start)
			return 0; 
	}
	return 1;
}

static void
checkport(int start, int end)
{
	/* standard vga regs are OK */
	if(start >= 0x2b0 && end <= 0x2df+1)
		return;
	if(start >= 0x3c0 && end <= 0x3da+1)
		return;

	if(iounused(start, end))
		return;
	error(Eperm);
}

static Chan*
archattach(char* spec)
{
	return devattach('P', spec);
}

Walkqid*
archwalk(Chan* c, Chan *nc, char** name, int nname)
{
	return devwalk(c, nc, name, nname, archdir, narchdir, devgen);
}

static int
archstat(Chan* c, uchar* dp, int n)
{
	return devstat(c, dp, n, archdir, narchdir, devgen);
}

static Chan*
archopen(Chan* c, int omode)
{
	return devopen(c, omode, archdir, narchdir, devgen);
}

static void
archclose(Chan*)
{
}

enum
{
	Linelen= 31,
};

static long
archread(Chan *c, void *a, long n, vlong offset)
{
	char *buf, *p;
	int port;
	ushort *sp;
	ulong *lp;
	IOMap *m;
	Rdwrfn *fn;

	switch((ulong)c->qid.path){

	case Qdir:
		return devdirread(c, a, n, archdir, narchdir, devgen);

	case Qiob:
		port = offset;
		checkport(offset, offset+n);
		for(p = a; port < offset+n; port++)
			*p++ = inb(port);
		return n;

	case Qiow:
		if(n & 1)
			error(Ebadarg);
		checkport(offset, offset+n);
		sp = a;
		for(port = offset; port < offset+n; port += 2)
			*sp++ = ins(port);
		return n;

	case Qiol:
		if(n & 3)
			error(Ebadarg);
		checkport(offset, offset+n);
		lp = a;
		for(port = offset; port < offset+n; port += 4)
			*lp++ = inl(port);
		return n;

	case Qioalloc:
		break;

	default:
		if(c->qid.path < narchdir && (fn = readfn[c->qid.path]))
			return fn(c, a, n, offset);
		error(Eperm);
		break;
	}

	if((buf = malloc(n)) == nil)
		error(Enomem);
	p = buf;
	n = n/Linelen;
	offset = offset/Linelen;

	lock(&iomap);
	for(m = iomap.m; n > 0 && m != nil; m = m->next){
		if(offset-- > 0)
			continue;
		sprint(p, "%8lux %8lux %-12.12s\n", m->start, m->end-1, m->tag);
		p += Linelen;
		n--;
	}
	unlock(&iomap);

	n = p - buf;
	memmove(a, buf, n);
	free(buf);

	return n;
}

static long
archwrite(Chan *c, void *a, long n, vlong offset)
{
	char *p;
	int port;
	ushort *sp;
	ulong *lp;
	Rdwrfn *fn;

	switch((ulong)c->qid.path){

	case Qiob:
		p = a;
		checkport(offset, offset+n);
		for(port = offset; port < offset+n; port++)
			outb(port, *p++);
		return n;

	case Qiow:
		if(n & 1)
			error(Ebadarg);
		checkport(offset, offset+n);
		sp = a;
		for(port = offset; port < offset+n; port += 2)
			outs(port, *sp++);
		return n;

	case Qiol:
		if(n & 3)
			error(Ebadarg);
		checkport(offset, offset+n);
		lp = a;
		for(port = offset; port < offset+n; port += 4)
			outl(port, *lp++);
		return n;

	default:
		if(c->qid.path < narchdir && (fn = writefn[c->qid.path]))
			return fn(c, a, n, offset);
		error(Eperm);
		break;
	}
	return 0;
}

Dev archdevtab = {
	'P',
	"arch",

	devreset,
	devinit,
	devshutdown,
	archattach,
	archwalk,
	archstat,
	archopen,
	devcreate,
	archclose,
	archread,
	devbread,
	archwrite,
	devbwrite,
	devremove,
	devwstat,
};

/*
 *  the following is a generic version of the
 *  architecture specific stuff
 */