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disk/format: FAT32 support

--- a/sys/man/8/prep

+++ b/sys/man/8/prep

@@ -713,10 +713,6 @@

 .IR 9boot (8),

 .IR partfs (8)

 .SH BUGS

-.I Format

-can create FAT12 and FAT16

-file systems, but not FAT32 file systems.

-.PP

 If

 .L "prep -p"

 doesn't find a Plan 9 partition table,

--- a/sys/src/cmd/disk/format.c

+++ b/sys/src/cmd/disk/format.c

@@ -45,13 +45,33 @@

 	uchar	nheads[2];

 	uchar	nhidden[4];

 	uchar	bigvolsize[4];

-	uchar	driveno;

-	uchar	reserved0;

-	uchar	bootsig;

-	uchar	volid[4];

-	uchar	label[11];

-	uchar	type[8];

+	union {

+		struct {

+			uchar	driveno;

+			uchar	reserved0;

+			uchar	bootsig;

+			uchar	volid[4];

+			uchar	label[11];

+			uchar	type[8];

+		};

+		struct {

+			uchar	fatsize[4];

+			uchar	flags[2];

+			uchar	ver[2];

+			uchar	rootclust[4];

+			uchar	fsinfo[2];

+			uchar	bootbak[2];

+			uchar	reserved0[12];

+			uchar	driveno;

+			uchar	reserved1;

+			uchar	bootsig;

+			uchar	volid[4];

+			uchar	label[11];

+			uchar	type[8];

+		} fat32;

+	};

 };

+

 #define	PUTSHORT(p, v) { (p)[1] = (v)>>8; (p)[0] = (v); }

 #define	PUTLONG(p, v) { PUTSHORT((p), (v)); PUTSHORT((p)+2, (v)>>16); }

 #define	GETSHORT(p)	(((p)[1]<<8)|(p)[0])

@@ -533,6 +553,12 @@

 				rootfiles = 512;

 				rootsecs = rootfiles/(secsize/sizeof(Dosdir));

 			}

+			if(fatbits == 32){

+				rootsecs -= (rootsecs % clustersize);

+				if(rootsecs <= 0)

+					rootsecs = clustersize;

+				rootfiles = rootsecs * (secsize/sizeof(Dosdir));

+			}

 			data = nresrv + 2*fatsecs + (rootfiles*sizeof(Dosdir) + secsize-1)/secsize;

 			newclusters = 2 + (volsecs - data)/clustersize;

 			if(newclusters == clusters)

@@ -547,43 +573,49 @@

 if(chatty) print("try %d fatbits => %d clusters of %d\n", fatbits, clusters, clustersize);

 		switch(fatbits){

 		case 12:

-			if(clusters >= 4087){

+			if(clusters >= 0xff7){

 				fatbits = 16;

 				goto Tryagain;

 			}

 			break;

 		case 16:

-			if(clusters >= 65527)

-				fatal("disk too big; implement fat32");

+			if(clusters >= 0xfff7){

+				fatbits = 32;

+				goto Tryagain;

+			}

 			break;

+		case 32:

+			if(clusters >= 0xffffff7)

+				fatal("filesystem too big");

+			break;

 		}

 		PUTSHORT(b->sectsize, secsize);

 		b->clustsize = clustersize;

 		PUTSHORT(b->nresrv, nresrv);

 		b->nfats = 2;

-		PUTSHORT(b->rootsize, rootfiles);

-		if(volsecs < (1<<16))

-			PUTSHORT(b->volsize, volsecs);

+		PUTSHORT(b->rootsize, fatbits == 32 ? 0 : rootfiles);

+		PUTSHORT(b->volsize, volsecs >= (1<<16) ? 0 : volsecs);

 		b->mediadesc = t->media;

-		PUTSHORT(b->fatsize, fatsecs);

+		PUTSHORT(b->fatsize, fatbits == 32 ? 0 : fatsecs);

 		PUTSHORT(b->trksize, t->sectors);

 		PUTSHORT(b->nheads, t->heads);

 		PUTLONG(b->nhidden, disk->offset);

 		PUTLONG(b->bigvolsize, volsecs);

-		/*

-		 * Extended BIOS Parameter Block.

-		 */

-		if(t->media == 0xF8)

-			b->driveno = getdriveno(disk);

-		else

-			b->driveno = 0;

-if(chatty) print("driveno = %ux\n", b->driveno);

-	

-		b->bootsig = 0x29;

-		memmove(b->label, label, sizeof(b->label));

 		sprint(r, "FAT%d    ", fatbits);

-		memmove(b->type, r, sizeof(b->type));

+		if(fatbits == 32){

+			PUTLONG(b->fat32.fatsize, fatsecs);

+			PUTLONG(b->fat32.rootclust, 2);

+			b->fat32.bootsig = 0x29;

+			b->fat32.driveno = (t->media == 0xF8) ? getdriveno(disk) : 0;

+			memmove(b->fat32.label, label, sizeof(b->fat32.label));

+			memmove(b->fat32.type, r, sizeof(b->fat32.type));

+		} else {

+			b->bootsig = 0x29;

+			b->driveno = (t->media == 0xF8) ? getdriveno(disk) : 0;

+			memmove(b->label, label, sizeof(b->label));

+			memmove(b->type, r, sizeof(b->type));

+		}

 	}

 	buf[secsize-2] = 0x55;

@@ -617,13 +649,33 @@

 	fat[0] = t->media;

 	fat[1] = 0xff;

 	fat[2] = 0xff;

-	if(fatbits == 16)

+	if(fatbits >= 16)

 		fat[3] = 0xff;

+	if(fatbits == 32){

+		fat[4] = 0xff;

+		fat[5] = 0xff;

+		fat[6] = 0xff;

+		fat[7] = 0xff;

+	}

 	fatlast = 1;

 	if(seek(disk->wfd, 2*fatsecs*secsize, 1) < 0)	/* 2 fats */

 		fatal("seek to root: %r");

 if(chatty) print("root @%lluX\n", seek(disk->wfd, 0LL, 1));

+	if(fatbits == 32){

+		/*

+		 * allocate clusters for root directory

+		 */

+		if(rootsecs % clustersize)

+			abort();

+		length = rootsecs / clustersize;

+		if(clustalloc(Sof) != 2)

+			abort();

+		for(n = 0; n < length-1; n++)

+			clustalloc(0);

+		clustalloc(Eof);

+	}

+

 	/*

 	 *  allocate an in memory root

 	 */

@@ -730,7 +782,7 @@

 	ulong o, x;

 	if(flag != Sof){

-		x = (flag == Eof) ? 0xffff : (fatlast+1);

+		x = (flag == Eof) ? ~0 : (fatlast+1);

 		if(fatbits == 12){

 			x &= 0xfff;

 			o = (3*fatlast)/2;

@@ -741,10 +793,20 @@

 				fat[o] = x;

 				fat[o+1] = (fat[o+1]&0xf0) | ((x>>8) & 0x0F);

 			}

-		} else {

+		}

+		else if(fatbits == 16){

+			x &= 0xffff;

 			o = 2*fatlast;

 			fat[o] = x;

 			fat[o+1] = x>>8;

+		}

+		else if(fatbits == 32){

+			x &= 0xfffffff;

+			o = 4*fatlast;

+			fat[o] = x;

+			fat[o+1] = x>>8;

+			fat[o+2] = x>>16;

+			fat[o+3] = x>>24;

 		}

 	}