iso: Allow 512 byte sector size

Real CD-ROMs are pretty obsolete these days. Usually people still keep
iso files around, but just put them on USB sticks or SD cards and expect
them to "just work".

To support this use case with El Torito images, add support for 512 byte
sector size to the iso parsing code.

Signed-off-by: Alexander Graf <agraf@suse.de>

disk/part_iso.c

@@ -26,6 +26,25 @@
 
 static unsigned char tmpbuf[CD_SECTSIZE];
 
+unsigned long iso_dread(struct blk_desc *block_dev, lbaint_t start,
+                        lbaint_t blkcnt, void *buffer)
+{
+	unsigned long ret;
+
+	if (block_dev->blksz == 512) {
+		/* Convert from 2048 to 512 sector size */
+		start *= 4;
+		blkcnt *= 4;
+	}
+
+	ret = blk_dread(block_dev, start, blkcnt, buffer);
+
+	if (block_dev->blksz == 512)
+		ret /= 4;
+
+	return ret;
+}
+
 /* only boot records will be listed as valid partitions */
 int part_get_info_iso_verb(struct blk_desc *dev_desc, int part_num,
 			   disk_partition_t *info, int verb)
@@ -39,12 +58,12 @@ int part_get_info_iso_verb(struct blk_desc *dev_desc, int part_num,
 	iso_val_entry_t *pve = (iso_val_entry_t *)tmpbuf;
 	iso_init_def_entry_t *pide;
 
-	if (dev_desc->blksz != CD_SECTSIZE)
+	if ((dev_desc->blksz != CD_SECTSIZE) && (dev_desc->blksz != 512))
 		return -1;
 
 	/* the first sector (sector 0x10) must be a primary volume desc */
 	blkaddr=PVD_OFFSET;
-	if (blk_dread(dev_desc, PVD_OFFSET, 1, (ulong *)tmpbuf) != 1)
+	if (iso_dread(dev_desc, PVD_OFFSET, 1, (ulong *)tmpbuf) != 1)
 		return -1;
 	if(ppr->desctype!=0x01) {
 		if(verb)
@@ -64,7 +83,7 @@ int part_get_info_iso_verb(struct blk_desc *dev_desc, int part_num,
 	PRINTF(" Lastsect:%08lx\n",lastsect);
 	for(i=blkaddr;i<lastsect;i++) {
 		PRINTF("Reading block %d\n", i);
-		if (blk_dread(dev_desc, i, 1, (ulong *)tmpbuf) != 1)
+		if (iso_dread(dev_desc, i, 1, (ulong *)tmpbuf) != 1)
 			return -1;
 		if(ppr->desctype==0x00)
 			break; /* boot entry found */
@@ -84,7 +103,7 @@ int part_get_info_iso_verb(struct blk_desc *dev_desc, int part_num,
 	}
 	bootaddr = get_unaligned_le32(pbr->pointer);
 	PRINTF(" Boot Entry at: %08lX\n",bootaddr);
-	if (blk_dread(dev_desc, bootaddr, 1, (ulong *)tmpbuf) != 1) {
+	if (iso_dread(dev_desc, bootaddr, 1, (ulong *)tmpbuf) != 1) {
 		if(verb)
 			printf ("** Can't read Boot Entry at %lX on %d:%d **\n",
 				bootaddr, dev_desc->devnum, part_num);
@@ -192,7 +211,14 @@ found:
 	}
 	newblkaddr = get_unaligned_le32(pide->rel_block_addr);
 	info->start=newblkaddr;
-	PRINTF(" part %d found @ %lx size %lx\n",part_num,newblkaddr,info->size);
+
+	if (dev_desc->blksz == 512) {
+		info->size *= 4;
+		info->start *= 4;
+		info->blksz = 512;
+	}
+
+	PRINTF(" part %d found @ %lx size %lx\n",part_num,info->start,info->size);
 	return 0;
 }