mtd: docg3 reduce read alignment burden

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=d107bc34f4953852834f086968fc7963125d6943
Commit:     d107bc34f4953852834f086968fc7963125d6943
Parent:     cfe781946dac7f5ff42e23cd7054c75e7201fbdc
Author:     Robert Jarzmik <robert.jarzmik at free.fr>
AuthorDate: Sun Mar 11 11:28:45 2012 +0100
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Tue Mar 27 00:53:43 2012 +0100

    mtd: docg3 reduce read alignment burden
    
    The read function was so far requiring the reads to be aligned on page
    boundaries, and be page length multiples in size. Relieve these
    constraints to ease the userspace ubifs programs runs, which read ubifs
    headers of 64 bytes.
    
    Artem: squashed a later fix from Robert Jarzmik into this patch.
    
    Signed-off-by: Robert Jarzmik <robert.jarzmik at free.fr>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/devices/docg3.c |   21 +++++++++++++--------
 1 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
index 3eafef3..2c1d0fc 100644
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -734,7 +734,7 @@ err:
  * doc_read_page_getbytes - Reads bytes from a prepared page
  * @docg3: the device
  * @len: the number of bytes to be read (must be a multiple of 4)
- * @buf: the buffer to be filled in
+ * @buf: the buffer to be filled in (or NULL is forget bytes)
  * @first: 1 if first time read, DOC_READADDRESS should be set
  *
  */
@@ -849,7 +849,7 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 			struct mtd_oob_ops *ops)
 {
 	struct docg3 *docg3 = mtd->priv;
-	int block0, block1, page, ret, ofs = 0;
+	int block0, block1, page, ret, skip, ofs = 0;
 	u8 *oobbuf = ops->oobbuf;
 	u8 *buf = ops->datbuf;
 	size_t len, ooblen, nbdata, nboob;
@@ -869,8 +869,7 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 
 	doc_dbg("doc_read_oob(from=%lld, mode=%d, data=(%p:%zu), oob=(%p:%zu))\n",
 		from, ops->mode, buf, len, oobbuf, ooblen);
-	if ((len % DOC_LAYOUT_PAGE_SIZE) || (ooblen % DOC_LAYOUT_OOB_SIZE) ||
-	    (from % DOC_LAYOUT_PAGE_SIZE))
+	if (ooblen % DOC_LAYOUT_OOB_SIZE)
 		return -EINVAL;
 
 	ret = -EINVAL;
@@ -882,10 +881,11 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 	ops->oobretlen = 0;
 	ops->retlen = 0;
 	ret = 0;
+	skip = from % DOC_LAYOUT_PAGE_SIZE;
 	while (!ret && (len > 0 || ooblen > 0)) {
-		calc_block_sector(from, &block0, &block1, &page, &ofs,
+		calc_block_sector(from - skip, &block0, &block1, &page, &ofs,
 			docg3->reliable);
-		nbdata = min_t(size_t, len, (size_t)DOC_LAYOUT_PAGE_SIZE);
+		nbdata = min_t(size_t, len, DOC_LAYOUT_PAGE_SIZE - skip);
 		nboob = min_t(size_t, ooblen, (size_t)DOC_LAYOUT_OOB_SIZE);
 		ret = doc_read_page_prepare(docg3, block0, block1, page, ofs);
 		if (ret < 0)
@@ -893,10 +893,14 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 		ret = doc_read_page_ecc_init(docg3, DOC_ECC_BCH_TOTAL_BYTES);
 		if (ret < 0)
 			goto err_in_read;
-		ret = doc_read_page_getbytes(docg3, nbdata, buf, 1);
+		ret = doc_read_page_getbytes(docg3, skip, NULL, 1);
+		if (ret < skip)
+			goto err_in_read;
+		ret = doc_read_page_getbytes(docg3, nbdata, buf, 0);
 		if (ret < nbdata)
 			goto err_in_read;
-		doc_read_page_getbytes(docg3, DOC_LAYOUT_PAGE_SIZE - nbdata,
+		doc_read_page_getbytes(docg3,
+				       DOC_LAYOUT_PAGE_SIZE - nbdata - skip,
 				       NULL, 0);
 		ret = doc_read_page_getbytes(docg3, nboob, oobbuf, 0);
 		if (ret < nboob)
@@ -950,6 +954,7 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 		len -= nbdata;
 		ooblen -= nboob;
 		from += DOC_LAYOUT_PAGE_SIZE;
+		skip = 0;
 	}
 
 	return ret;