Only change devsd version number when media size changes.
Do not change when it is zero and remains zero.

Also, remove useless and confusing > lines in:

		switch(unit->state){
		...
		case Rawdata:
> 			if(unit->state != Rawdata)
> 				error(Ebadusefd);
			...
		}


Reference: /n/sources/patch/applied/devsd-version
Date: Mon May  7 16:08:12 CES 2007
Signed-off-by: rsc@swtch.com

--- /sys/src/9/port/devsd.c	Mon May  7 16:06:14 2007
+++ /sys/src/9/port/devsd.c	Mon May  7 16:06:14 2007
@@ -159,21 +159,31 @@
 	pp->vers++;
 }
 
-static int
-sdinitpart(SDunit* unit)
+static void
+sdincvers(SDunit *unit)
 {
-	int i, nf;
-	ulong start, end;
-	char *f[4], *p, *q, buf[10];
+	int i;
 
 	unit->vers++;
-	unit->sectors = unit->secsize = 0;
 	if(unit->part){
 		for(i = 0; i < unit->npart; i++){
 			unit->part[i].valid = 0;
 			unit->part[i].vers++;
 		}
 	}
+}
+
+static int
+sdinitpart(SDunit* unit)
+{
+	int nf;
+	ulong start, end;
+	char *f[4], *p, *q, buf[10];
+
+	if(unit->sectors > 0){
+		unit->sectors = unit->secsize = 0;
+		sdincvers(unit);
+	}
 
 	if(unit->inquiry[0] & 0xC0)
 		return 0;
@@ -190,6 +200,7 @@
 	if(unit->dev->ifc->online)
 		unit->dev->ifc->online(unit);
 	if(unit->sectors){
+		sdincvers(unit);
 		sdaddpart(unit, "data", 0, unit->sectors);
 
 		/*
@@ -1311,10 +1322,7 @@
 			error(Ebadusefd);
 
 		case Rawdata:
-			if(unit->state != Rawdata)
-				error(Ebadusefd);
 			unit->state = Rawstatus;
-
 			unit->req->write = 1;
 			n = sdrio(unit->req, a, n);
 		}