opendisk seemed to assume that memory was zeroed, so that part and h/c/s
were initially zero, but user-level malloc no longer does that.
changed to use mallocz.  scsi.c did include the memset
but i've changed it to use mallocz as well.

Reference: /n/sources/patch/applied/libdisk-zero
Date: Thu Sep  8 12:02:21 CES 2005

--- /sys/src/libdisk/scsi.c	Thu Sep  8 11:57:10 2005
+++ /sys/src/libdisk/scsi.c	Thu Sep  8 11:57:07 2005
@@ -308,13 +308,12 @@
 	if((p = strdup(buf+8)) == nil)
 		goto Error;
 
-	s = malloc(sizeof(*s));
+	s = mallocz(sizeof(*s), 1);
 	if(s == nil) {
 	Error1:
 		free(p);
 		goto Error;
 	}
-	memset(s, 0, sizeof(*s));
 
 	s->rawfd = rawfd;
 	s->inquire = p;
--- /sys/src/libdisk/disk.c	Thu Sep  8 11:57:22 2005
+++ /sys/src/libdisk/disk.c	Thu Sep  8 11:57:20 2005
@@ -272,7 +272,7 @@
 	char *p, *q;
 	Disk *d;
 
-	d = malloc(sizeof(*d));
+	d = mallocz(sizeof(*d), 1);
 	if(d == nil)
 		return nil;
 
@@ -347,4 +347,3 @@
 	d->type = Tfile;
 	return openfile(d);
 }
-