[MTD] [NAND] remove len/ooblen confusion.

As was discussed between Ricard Wanderlöf, David Woodhouse, Artem 
Bityutskiy and me, the current API for reading/writing OOB is confusing. 

The thing that introduces confusion is the need to specify ops.len 
together with ops.ooblen for reads/writes that concern only OOB not data 
area. So, ops.len is overloaded: when ops.datbuf != NULL it serves to 
specify the length of the data read, and when ops.datbuf == NULL, it 
serves to specify the full OOB read length.

The patch inlined below is the slightly updated version of the previous 
patch serving the same purpose, but with the new Artem's comments taken 
into account.

Artem, BTW, thanks a lot for your valuable input!

Signed-off-by: Vitaly Wool <vwool@ru.mvista.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/wbuf.c b/fs/jffs2/wbuf.c
index b9b7007..dcb18e9 100644
--- a/fs/jffs2/wbuf.c
+++ b/fs/jffs2/wbuf.c
@@ -968,8 +968,7 @@
 	int oobsize = c->mtd->oobsize;
 	struct mtd_oob_ops ops;
 
-	ops.len = NR_OOB_SCAN_PAGES * oobsize;
-	ops.ooblen = oobsize;
+	ops.ooblen = NR_OOB_SCAN_PAGES * oobsize;
 	ops.oobbuf = c->oobbuf;
 	ops.ooboffs = 0;
 	ops.datbuf = NULL;
@@ -982,10 +981,10 @@
 		return ret;
 	}
 
-	if (ops.retlen < ops.len) {
+	if (ops.oobretlen < ops.ooblen) {
 		D1(printk(KERN_WARNING "jffs2_check_oob_empty(): Read OOB "
 			  "returned short read (%zd bytes not %d) for block "
-			  "at %08x\n", ops.retlen, ops.len, jeb->offset));
+			  "at %08x\n", ops.oobretlen, ops.ooblen, jeb->offset));
 		return -EIO;
 	}
 
@@ -1004,7 +1003,7 @@
 	}
 
 	/* we know, we are aligned :) */
-	for (page = oobsize; page < ops.len; page += sizeof(long)) {
+	for (page = oobsize; page < ops.ooblen; page += sizeof(long)) {
 		long dat = *(long *)(&ops.oobbuf[page]);
 		if(dat != -1)
 			return 1;
@@ -1032,7 +1031,6 @@
 		return 2;
 	}
 
-	ops.len = oobsize;
 	ops.ooblen = oobsize;
 	ops.oobbuf = c->oobbuf;
 	ops.ooboffs = 0;
@@ -1047,10 +1045,10 @@
 		return ret;
 	}
 
-	if (ops.retlen < ops.len) {
+	if (ops.oobretlen < ops.ooblen) {
 		D1 (printk (KERN_WARNING "jffs2_check_nand_cleanmarker(): "
 			    "Read OOB return short read (%zd bytes not %d) "
-			    "for block at %08x\n", ops.retlen, ops.len,
+			    "for block at %08x\n", ops.oobretlen, ops.ooblen,
 			    jeb->offset));
 		return -EIO;
 	}
@@ -1089,8 +1087,7 @@
 	n.nodetype = cpu_to_je16(JFFS2_NODETYPE_CLEANMARKER);
 	n.totlen = cpu_to_je32(8);
 
-	ops.len = c->fsdata_len;
-	ops.ooblen = c->fsdata_len;;
+	ops.ooblen = c->fsdata_len;
 	ops.oobbuf = (uint8_t *)&n;
 	ops.ooboffs = c->fsdata_pos;
 	ops.datbuf = NULL;
@@ -1104,10 +1101,10 @@
 			  jeb->offset, ret));
 		return ret;
 	}
-	if (ops.retlen != ops.len) {
+	if (ops.oobretlen != ops.ooblen) {
 		D1(printk(KERN_WARNING "jffs2_write_nand_cleanmarker(): "
 			  "Short write for block at %08x: %zd not %d\n",
-			  jeb->offset, ops.retlen, ops.len));
+			  jeb->offset, ops.oobretlen, ops.ooblen));
 		return -EIO;
 	}
 	return 0;