[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: NVitaly Wool <vwool@ru.mvista.com>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>

drivers/mtd/inftlcore.c

@@ -163,10 +163,9 @@ int inftl_read_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 	ops.ooblen = len;
 	ops.oobbuf = buf;
 	ops.datbuf = NULL;
-	ops.len = len;
 
 	res = mtd->read_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
-	*retlen = ops.retlen;
+	*retlen = ops.oobretlen;
 	return res;
 }
 
@@ -184,10 +183,9 @@ int inftl_write_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 	ops.ooblen = len;
 	ops.oobbuf = buf;
 	ops.datbuf = NULL;
-	ops.len = len;
 
 	res = mtd->write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
-	*retlen = ops.retlen;
+	*retlen = ops.oobretlen;
 	return res;
 }
 

drivers/mtd/mtdchar.c

@@ -499,13 +499,12 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
 		if (ret)
 			return ret;
 
-		ops.len = buf.length;
 		ops.ooblen = buf.length;
 		ops.ooboffs = buf.start & (mtd->oobsize - 1);
 		ops.datbuf = NULL;
 		ops.mode = MTD_OOB_PLACE;
 
-		if (ops.ooboffs && ops.len > (mtd->oobsize - ops.ooboffs))
+		if (ops.ooboffs && ops.ooblen > (mtd->oobsize - ops.ooboffs))
 			return -EINVAL;
 
 		ops.oobbuf = kmalloc(buf.length, GFP_KERNEL);
@@ -520,7 +519,7 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
 		buf.start &= ~(mtd->oobsize - 1);
 		ret = mtd->write_oob(mtd, buf.start, &ops);
 
-		if (copy_to_user(argp + sizeof(uint32_t), &ops.retlen,
+		if (copy_to_user(argp + sizeof(uint32_t), &ops.oobretlen,
 				 sizeof(uint32_t)))
 			ret = -EFAULT;
 
@@ -548,7 +547,6 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
 		if (ret)
 			return ret;
 
-		ops.len = buf.length;
 		ops.ooblen = buf.length;
 		ops.ooboffs = buf.start & (mtd->oobsize - 1);
 		ops.datbuf = NULL;
@@ -564,10 +562,10 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
 		buf.start &= ~(mtd->oobsize - 1);
 		ret = mtd->read_oob(mtd, buf.start, &ops);
 
-		if (put_user(ops.retlen, (uint32_t __user *)argp))
+		if (put_user(ops.oobretlen, (uint32_t __user *)argp))
 			ret = -EFAULT;
-		else if (ops.retlen && copy_to_user(buf.ptr, ops.oobbuf,
-						    ops.retlen))
+		else if (ops.oobretlen && copy_to_user(buf.ptr, ops.oobbuf,
+						    ops.oobretlen))
 			ret = -EFAULT;
 
 		kfree(ops.oobbuf);

drivers/mtd/mtdconcat.c

@@ -247,7 +247,7 @@ concat_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 	struct mtd_oob_ops devops = *ops;
 	int i, err, ret = 0;
 
-	ops->retlen = 0;
+	ops->retlen = ops->oobretlen = 0;
 
 	for (i = 0; i < concat->num_subdev; i++) {
 		struct mtd_info *subdev = concat->subdev[i];
@@ -263,6 +263,7 @@ concat_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 
 		err = subdev->read_oob(subdev, from, &devops);
 		ops->retlen += devops.retlen;
+		ops->oobretlen += devops.oobretlen;
 
 		/* Save information about bitflips! */
 		if (unlikely(err)) {
@@ -278,14 +279,18 @@ concat_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 				return err;
 		}
 
+		if (devops.datbuf) {
 			devops.len = ops->len - ops->retlen;
 			if (!devops.len)
 				return ret;
-
-		if (devops.datbuf)
 			devops.datbuf += devops.retlen;
-		if (devops.oobbuf)
-			devops.oobbuf += devops.ooblen;
+		}
+		if (devops.oobbuf) {
+			devops.ooblen = ops->ooblen - ops->oobretlen;
+			if (!devops.ooblen)
+				return ret;
+			devops.oobbuf += ops->oobretlen;
+		}
 
 		from = 0;
 	}
@@ -321,14 +326,18 @@ concat_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops)
 		if (err)
 			return err;
 
+		if (devops.datbuf) {
 			devops.len = ops->len - ops->retlen;
 			if (!devops.len)
 				return 0;
-
-		if (devops.datbuf)
 			devops.datbuf += devops.retlen;
-		if (devops.oobbuf)
-			devops.oobbuf += devops.ooblen;
+		}
+		if (devops.oobbuf) {
+			devops.ooblen = ops->ooblen - ops->oobretlen;
+			if (!devops.ooblen)
+				return 0;
+			devops.oobbuf += devops.oobretlen;
+		}
 		to = 0;
 	}
 	return -EINVAL;

drivers/mtd/mtdpart.c

@@ -94,7 +94,7 @@ static int part_read_oob(struct mtd_info *mtd, loff_t from,
 
 	if (from >= mtd->size)
 		return -EINVAL;
-	if (from + ops->len > mtd->size)
+	if (ops->datbuf && from + ops->len > mtd->size)
 		return -EINVAL;
 	res = part->master->read_oob(part->master, from + part->offset, ops);
 
@@ -161,7 +161,7 @@ static int part_write_oob(struct mtd_info *mtd, loff_t to,
 
 	if (to >= mtd->size)
 		return -EINVAL;
-	if (to + ops->len > mtd->size)
+	if (ops->datbuf && to + ops->len > mtd->size)
 		return -EINVAL;
 	return part->master->write_oob(part->master, to + part->offset, ops);
 }

drivers/mtd/nand/nand_base.c

@@ -897,12 +897,11 @@ static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
  * @chip:	nand chip structure
  * @oob:	oob destination address
  * @ops:	oob ops structure
+ * @len:	size of oob to transfer
  */
 static uint8_t *nand_transfer_oob(struct nand_chip *chip, uint8_t *oob,
-				  struct mtd_oob_ops *ops)
+				  struct mtd_oob_ops *ops, size_t len)
 {
-	size_t len = ops->ooblen;
-
 	switch(ops->mode) {
 
 	case MTD_OOB_PLACE:
@@ -960,6 +959,7 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
 	int sndcmd = 1;
 	int ret = 0;
 	uint32_t readlen = ops->len;
+	uint32_t oobreadlen = ops->ooblen;
 	uint8_t *bufpoi, *oob, *buf;
 
 	stats = mtd->ecc_stats;
@@ -1006,10 +1006,17 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
 
 			if (unlikely(oob)) {
 				/* Raw mode does data:oob:data:oob */
-				if (ops->mode != MTD_OOB_RAW)
-					oob = nand_transfer_oob(chip, oob, ops);
-				else
-					buf = nand_transfer_oob(chip, buf, ops);
+				if (ops->mode != MTD_OOB_RAW) {
+					int toread = min(oobreadlen,
+						chip->ecc.layout->oobavail);
+					if (toread) {
+						oob = nand_transfer_oob(chip,
+							oob, ops, toread);
+						oobreadlen -= toread;
+					}
+				} else
+					buf = nand_transfer_oob(chip,
+						buf, ops, mtd->oobsize);
 			}
 
 			if (!(chip->options & NAND_NO_READRDY)) {
@@ -1056,6 +1063,8 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
 	}
 
 	ops->retlen = ops->len - (size_t) readlen;
+	if (oob)
+		ops->oobretlen = ops->ooblen - oobreadlen;
 
 	if (ret)
 		return ret;
@@ -1256,12 +1265,18 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
 	int page, realpage, chipnr, sndcmd = 1;
 	struct nand_chip *chip = mtd->priv;
 	int blkcheck = (1 << (chip->phys_erase_shift - chip->page_shift)) - 1;
-	int readlen = ops->len;
+	int readlen = ops->ooblen;
+	int len;
 	uint8_t *buf = ops->oobbuf;
 
 	DEBUG(MTD_DEBUG_LEVEL3, "nand_read_oob: from = 0x%08Lx, len = %i\n",
 	      (unsigned long long)from, readlen);
 
+	if (ops->mode == MTD_OOB_RAW)
+		len = mtd->oobsize;
+	else
+		len = chip->ecc.layout->oobavail;
+
 	chipnr = (int)(from >> chip->chip_shift);
 	chip->select_chip(mtd, chipnr);
 
@@ -1271,7 +1286,9 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
 
 	while(1) {
 		sndcmd = chip->ecc.read_oob(mtd, chip, page, sndcmd);
-		buf = nand_transfer_oob(chip, buf, ops);
+
+		len = min(len, readlen);
+		buf = nand_transfer_oob(chip, buf, ops, len);
 
 		if (!(chip->options & NAND_NO_READRDY)) {
 			/*
@@ -1286,7 +1303,7 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
 				nand_wait_ready(mtd);
 		}
 
-		readlen -= ops->ooblen;
+		readlen -= len;
 		if (!readlen)
 			break;
 
@@ -1308,7 +1325,7 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
 			sndcmd = 1;
 	}
 
-	ops->retlen = ops->len;
+	ops->oobretlen = ops->ooblen;
 	return 0;
 }
 
@@ -1329,7 +1346,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 	ops->retlen = 0;
 
 	/* Do not allow reads past end of device */
-	if ((from + ops->len) > mtd->size) {
+	if (ops->datbuf && (from + ops->len) > mtd->size) {
 		DEBUG(MTD_DEBUG_LEVEL0, "nand_read_oob: "
 		      "Attempt read beyond end of device\n");
 		return -EINVAL;
@@ -1654,6 +1671,8 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
 	}
 
 	ops->retlen = ops->len - writelen;
+	if (unlikely(oob))
+		ops->oobretlen = ops->ooblen;
 	return ret;
 }
 
@@ -1709,10 +1728,10 @@ static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
 	struct nand_chip *chip = mtd->priv;
 
 	DEBUG(MTD_DEBUG_LEVEL3, "nand_write_oob: to = 0x%08x, len = %i\n",
-	      (unsigned int)to, (int)ops->len);
+	      (unsigned int)to, (int)ops->ooblen);
 
 	/* Do not allow write past end of page */
-	if ((ops->ooboffs + ops->len) > mtd->oobsize) {
+	if ((ops->ooboffs + ops->ooblen) > mtd->oobsize) {
 		DEBUG(MTD_DEBUG_LEVEL0, "nand_write_oob: "
 		      "Attempt to write past end of page\n");
 		return -EINVAL;
@@ -1748,7 +1767,7 @@ static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
 	if (status)
 		return status;
 
-	ops->retlen = ops->len;
+	ops->oobretlen = ops->ooblen;
 
 	return 0;
 }
@@ -1768,7 +1787,7 @@ static int nand_write_oob(struct mtd_info *mtd, loff_t to,
 	ops->retlen = 0;
 
 	/* Do not allow writes past end of device */
-	if ((to + ops->len) > mtd->size) {
+	if (ops->datbuf && (to + ops->len) > mtd->size) {
 		DEBUG(MTD_DEBUG_LEVEL0, "nand_read_oob: "
 		      "Attempt read beyond end of device\n");
 		return -EINVAL;

drivers/mtd/nand/nand_bbt.c

@@ -333,7 +333,6 @@ static int scan_block_fast(struct mtd_info *mtd, struct nand_bbt_descr *bd,
 	struct mtd_oob_ops ops;
 	int j, ret;
 
-	ops.len = mtd->oobsize;
 	ops.ooblen = mtd->oobsize;
 	ops.oobbuf = buf;
 	ops.ooboffs = 0;
@@ -676,10 +675,10 @@ static int write_bbt(struct mtd_info *mtd, uint8_t *buf,
 				       "bad block table\n");
 			}
 			/* Read oob data */
-			ops.len = (len >> this->page_shift) * mtd->oobsize;
+			ops.ooblen = (len >> this->page_shift) * mtd->oobsize;
 			ops.oobbuf = &buf[len];
 			res = mtd->read_oob(mtd, to + mtd->writesize, &ops);
-			if (res < 0 || ops.retlen != ops.len)
+			if (res < 0 || ops.oobretlen != ops.ooblen)
 				goto outerr;
 
 			/* Calc the byte offset in the buffer */

drivers/mtd/nftlcore.c

@@ -147,10 +147,9 @@ int nftl_read_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 	ops.ooblen = len;
 	ops.oobbuf = buf;
 	ops.datbuf = NULL;
-	ops.len = len;
 
 	res = mtd->read_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
-	*retlen = ops.retlen;
+	*retlen = ops.oobretlen;
 	return res;
 }
 
@@ -168,10 +167,9 @@ int nftl_write_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 	ops.ooblen = len;
 	ops.oobbuf = buf;
 	ops.datbuf = NULL;
-	ops.len = len;
 
 	res = mtd->write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
-	*retlen = ops.retlen;
+	*retlen = ops.oobretlen;
 	return res;
 }
 

drivers/mtd/ssfdc.c

@@ -172,13 +172,12 @@ static int read_raw_oob(struct mtd_info *mtd, loff_t offs, uint8_t *buf)
 
 	ops.mode = MTD_OOB_RAW;
 	ops.ooboffs = 0;
-	ops.ooblen = mtd->oobsize;
-	ops.len = OOB_SIZE;
+	ops.ooblen = OOB_SIZE;
 	ops.oobbuf = buf;
 	ops.datbuf = NULL;
 
 	ret = mtd->read_oob(mtd, offs, &ops);
-	if (ret < 0 || ops.retlen != OOB_SIZE)
+	if (ret < 0 || ops.oobretlen != OOB_SIZE)
 		return -1;
 
 	return 0;

fs/jffs2/wbuf.c

@@ -968,8 +968,7 @@ int jffs2_check_oob_empty(struct jffs2_sb_info *c,
 	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 @@ int jffs2_check_oob_empty(struct jffs2_sb_info *c,
 		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 @@ int jffs2_check_oob_empty(struct jffs2_sb_info *c,
 	}
 
 	/* 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 @@ int jffs2_check_nand_cleanmarker (struct jffs2_sb_info *c,
 		return 2;
 	}
 
-	ops.len = oobsize;
 	ops.ooblen = oobsize;
 	ops.oobbuf = c->oobbuf;
 	ops.ooboffs = 0;
@@ -1047,10 +1045,10 @@ int jffs2_check_nand_cleanmarker (struct jffs2_sb_info *c,
 		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 @@ int jffs2_write_nand_cleanmarker(struct jffs2_sb_info *c,
 	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 @@ int jffs2_write_nand_cleanmarker(struct jffs2_sb_info *c,
 			  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;

include/linux/mtd/mtd.h

@@ -75,15 +75,12 @@ typedef enum {
  * struct mtd_oob_ops - oob operation operands
  * @mode:	operation mode
  *
- * @len:	number of bytes to write/read. When a data buffer is given
- *		(datbuf != NULL) this is the number of data bytes. When
- *		no data buffer is available this is the number of oob bytes.
+ * @len:	number of data bytes to write/read
  *
- * @retlen:	number of bytes written/read. When a data buffer is given
- *		(datbuf != NULL) this is the number of data bytes. When
- *		no data buffer is available this is the number of oob bytes.
+ * @retlen:	number of data bytes written/read
  *
- * @ooblen:	number of oob bytes per page
+ * @ooblen:	number of oob bytes to write/read
+ * @oobretlen:	number of oob bytes written/read
  * @ooboffs:	offset of oob data in the oob area (only relevant when
  *		mode = MTD_OOB_PLACE)
  * @datbuf:	data buffer - if NULL only oob data are read/written
@@ -94,6 +91,7 @@ struct mtd_oob_ops {
 	size_t		len;
 	size_t		retlen;
 	size_t		ooblen;
+	size_t		oobretlen;
 	uint32_t	ooboffs;
 	uint8_t		*datbuf;
 	uint8_t		*oobbuf;