mtd: nand: remove NAND_BBT_SCANEMPTY

NAND_BBT_SCANEMPTY is a strange, badly-supported option with omap as its
single remaining user.

NAND_BBT_SCANEMPTY was likely used by accident in omap2[1]. And anyway,
omap2 doesn't scan the chip for bad blocks (courtesy of
NAND_SKIP_BBTSCAN), and so its use of this option is irrelevant.

This patch drops the NAND_BBT_SCANEMPTY option.

[1] http://lists.infradead.org/pipermail/linux-mtd/2012-July/042902.html

Signed-off-by: Brian Norris <[e-mail]>
Cc: Ivan Djelic <[e-mail]>
Signed-off-by: Artem Bityutskiy <[e-mail]>
Signed-off-by: David Woodhouse <[e-mail]>

Documentation/DocBook/mtdnand.tmpl

···
 #define NAND_BBT_CREATE		0x00000200
 /* Search good / bad pattern through all pages of a block */
 #define NAND_BBT_SCANALLPAGES	0x00000400
-/* Scan block empty during good / bad block scan */
-#define NAND_BBT_SCANEMPTY	0x00000800
 /* Write bbt if neccecary */
 #define NAND_BBT_WRITE		0x00001000
 /* Read and write back block contents when writing bbt */

drivers/mtd/nand/nand_bbt.c

···
  * @td: search pattern descriptor
  *
  * Check for a pattern at the given place. Used to search bad block tables and
- * good / bad block identifiers. If the SCAN_EMPTY option is set then check, if
- * all bytes except the pattern area contain 0xff.
+ * good / bad block identifiers.
  */
 static int check_pattern(uint8_t *buf, int len, int paglen, struct nand_bbt_descr *td)
 {
-	int end = 0;
-	uint8_t *p = buf;
-
 	if (td->options & NAND_BBT_NO_OOB)
 		return check_pattern_no_oob(buf, td);
 
-	end = paglen + td->offs;
-	if (td->options & NAND_BBT_SCANEMPTY)
-		if (memchr_inv(p, 0xff, end))
-			return -1;
-	p += end;
-
 	/* Compare the pattern */
-	if (memcmp(p, td->pattern, td->len))
+	if (memcmp(buf + paglen + td->offs, td->pattern, td->len))
 		return -1;
 
-	if (td->options & NAND_BBT_SCANEMPTY) {
-		p += td->len;
-		end += td->len;
-		if (memchr_inv(p, 0xff, len - end))
-			return -1;
-	}
 	return 0;
 }
 
···
 	else
 		numpages = 1;
 
-	if (!(bd->options & NAND_BBT_SCANEMPTY)) {
-		/* We need only read few bytes from the OOB area */
-		scanlen = 0;
-		readlen = bd->len;
-	} else {
-		/* Full page content should be read */
-		scanlen = mtd->writesize + mtd->oobsize;
-		readlen = numpages * mtd->writesize;
-	}
+	/* We need only read few bytes from the OOB area */
+	scanlen = 0;
+	readlen = bd->len;
 
 	if (chip == -1) {
 		numblocks = mtd->size >> this->bbt_erase_shift;
···
 {
 	struct nand_chip *this = mtd->priv;
 
-	bd->options &= ~NAND_BBT_SCANEMPTY;
 	return create_bbt(mtd, this->buffers->databuf, bd, -1);
 }
 

drivers/mtd/nand/omap2.c

···
  */
 static uint8_t scan_ff_pattern[] = { 0xff };
 static struct nand_bbt_descr bb_descrip_flashbased = {
-	.options = NAND_BBT_SCANEMPTY | NAND_BBT_SCANALLPAGES,
+	.options = NAND_BBT_SCANALLPAGES,
 	.offs = 0,
 	.len = 1,
 	.pattern = scan_ff_pattern,

drivers/mtd/onenand/onenand_bbt.c

···
 {
 	struct onenand_chip *this = mtd->priv;
 
-        bd->options &= ~NAND_BBT_SCANEMPTY;
 	return create_bbt(mtd, this->page_buf, bd, -1);
 }
 

include/linux/mtd/bbm.h

···
 #define NAND_BBT_CREATE_EMPTY	0x00000400
 /* Search good / bad pattern through all pages of a block */
 #define NAND_BBT_SCANALLPAGES	0x00000800
-/* Scan block empty during good / bad block scan */
-#define NAND_BBT_SCANEMPTY	0x00001000
 /* Write bbt if neccecary */
 #define NAND_BBT_WRITE		0x00002000
 /* Read and write back block contents when writing bbt */