[PATCH V4 7/7] drivers/mtd: add the mtdraw device (data+oob)

[Robert Jarzmik <robert.jarzmik@free.fr>]

Add a device to read and write to MTD data and oob
(/dev/mtdraw<N>).

The device is constrained in a separate source file, so that
further improvement of commands (such as nandwrite) could
make it useless, and easy to remove.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
 drivers/mtd/Kconfig  |    6 +
 drivers/mtd/Makefile |    5 +-
 drivers/mtd/mtdraw.c |  303 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 312 insertions(+), 2 deletions(-)
 create mode 100644 drivers/mtd/mtdraw.c

diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index a130c74..9137cde 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -14,6 +14,12 @@ config MTD_OOB_DEVICE
 	default y
 	prompt "Create a device for reading the OOB data"
 
+config MTD_RAW_DEVICE
+	bool
+	select NAND_READ_OOB
+	default n
+	prompt "mtdraw device to read/write both data+oob"
+
 source "drivers/mtd/nand/Kconfig"
 source "drivers/mtd/ubi/Kconfig"
 
diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index d41ffd4..67741f4 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -1,5 +1,6 @@
-obj-$(CONFIG_NAND)	+= nand/
-obj-$(CONFIG_UBI)	+= ubi/
+obj-$(CONFIG_NAND)			+= nand/
+obj-$(CONFIG_UBI)			+= ubi/
 obj-$(CONFIG_PARTITION_NEED_MTD)	+= partition.o
 obj-$(CONFIG_MTD)			+= core.o
 obj-$(CONFIG_MTD_OOB_DEVICE)		+= mtdoob.o
+obj-$(CONFIG_MTD_RAW_DEVICE)		+= mtdraw.o
diff --git a/drivers/mtd/mtdraw.c b/drivers/mtd/mtdraw.c
new file mode 100644
index 0000000..b1cce3d
--- /dev/null
+++ b/drivers/mtd/mtdraw.c
@@ -0,0 +1,303 @@
+/*
+ * MTD raw device
+ *
+ * Copyright (C) 2011 Robert Jarzmik
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Adds a character devices :
+ *  - mtdraw<N>
+ *
+ * Device mtd_raw<N> provides acces to the MTD "pages+OOB". For example if a MTD
+ * has pages of 512 bytes and OOB of 16 bytes, mtd_oob<N> will be made of blocks
+ * of 528 bytes, with page data being followed by OOB.
+ * The layout will be: <page0> <oob0> <page1> <oob1> ... <pageN> <oobN>.
+ * This means that a read at offset 516 of 20 bytes will give the 12 last bytes
+ * of the OOB of page0, and the 8 first bytes of page1.
+ * Same thing applies for writes, which have to be page+oob aligned (ie. offset
+ * and size should be multiples of (mtd->writesize + mtd->oobsize)).
+ */
+
+#include <common.h>
+#include <init.h>
+#include <malloc.h>
+#include <ioctl.h>
+#include <errno.h>
+#include <linux/mtd/mtd.h>
+
+#include "mtd.h"
+
+/* Must be a multiple of the largest NAND page size */
+#define RAW_WRITEBUF_SIZE	4096
+
+/**
+ * mtdraw - mtdraw device private data
+ * @cdev: character device "mtdraw<N>"
+ * @mtd: MTD device to handle read/writes/erases
+ *
+ * @writebuf: buffer to handle unaligned writes (ie. writes of sizes which are
+ * not multiples of MTD (writesize+oobsize)
+ * @write_fill: number of bytes in writebuf
+ * @write_ofs: offset in character device (mtdraw) where last write(s) stored
+ * bytes because of unaligned writes (ie. remain of writesize+oobsize write)
+ *
+ * The mtdraw device must allow unaligned writes. This is enabled by a write buffer which gathers data to issue mtd->write_oob() with full page+oob data.
+ * Suppose writesize=512, oobsize=16.
+ * A first write of 512 bytes triggers:
+ *  - write_ofs = offset of write()
+ *  - write_fill = 512
+ *  - copy of the 512 provided bytes into writebuf
+ *  - no actual mtd->write if done
+ * A second write of 512 bytes triggers:
+ *  - copy of the 16 first bytes into writebuf
+ *  - a mtd->write_oob() from writebuf
+ *  - empty writebuf
+ *  - copy the remaining 496 bytes into writebuf
+ *    => write_fill = 496, write_ofs = offset + 528
+ * Etc ...
+ */
+struct mtdraw {
+	struct cdev cdev;
+	struct mtd_info *mtd;
+	void *writebuf;
+	int write_fill;
+	int write_ofs;
+};
+
+static struct mtdraw *to_mtdraw(struct cdev *cdev)
+{
+	return cdev->priv;
+}
+
+static struct mtd_info *to_mtd(struct cdev *cdev)
+{
+	struct mtdraw *mtdraw = to_mtdraw(cdev);
+	return mtdraw->mtd;
+}
+
+static ssize_t mtdraw_read_unaligned(struct mtd_info *mtd, void *dst,
+				     size_t count, int skip, ulong offset)
+{
+	struct mtd_oob_ops ops;
+	ssize_t ret;
+	int partial = 0;
+	void *tmp = dst;
+
+	if (skip || count < mtd->writesize + mtd->oobsize)
+		partial = 1;
+	if (partial)
+		tmp = malloc(mtd->writesize + mtd->oobsize);
+	if (!tmp)
+		return -ENOMEM;
+	ops.mode = MTD_OOB_RAW;
+	ops.datbuf = tmp;
+	ops.len = mtd->writesize;
+	ops.oobbuf = tmp + mtd->writesize;
+	ops.ooblen = mtd->oobsize;
+	ret = mtd->read_oob(mtd, offset, &ops);
+	if (ret)
+		goto err;
+	if (partial)
+		memcpy(dst, tmp + skip, count);
+	ret = count;
+err:
+	if (partial)
+		free(tmp);
+
+	return ret;
+}
+
+static ssize_t mtdraw_read(struct cdev *cdev, void *buf, size_t count,
+			    ulong offset, ulong flags)
+{
+	struct mtd_info *mtd = to_mtd(cdev);
+	ssize_t retlen = 0, ret = 1, toread;
+	ulong numpage;
+	int skip;
+
+	numpage = offset / (mtd->writesize + mtd->oobsize);
+	skip = offset % (mtd->writesize + mtd->oobsize);
+
+	while (ret > 0 && count > 0) {
+		toread = min_t(int, count, mtd->writesize + mtd->oobsize);
+		ret = mtdraw_read_unaligned(mtd, buf, toread,
+					    skip, numpage++ * mtd->writesize);
+		buf += ret;
+		skip = 0;
+		count -= ret;
+		retlen += ret;
+	}
+	if (ret < 0)
+		printf("err %d\n", ret);
+	else
+		ret = retlen;
+	return ret;
+}
+
+#ifdef CONFIG_MTD_WRITE
+static ssize_t mtdraw_blkwrite(struct mtd_info *mtd, const void *buf,
+			       ulong offset)
+{
+	struct mtd_oob_ops ops;
+	int ret;
+
+	ops.mode = MTD_OOB_RAW;
+	ops.datbuf = (void *)buf;
+	ops.len = mtd->writesize;
+	ops.oobbuf = (void *)buf + mtd->writesize;
+	ops.ooblen = mtd->oobsize;
+	ret = mtd->write_oob(mtd, offset, &ops);
+	if (!ret)
+		ret = ops.retlen + ops.oobretlen;
+	return ret;
+}
+
+static void mtdraw_fillbuf(struct mtdraw *mtdraw, const void *src, int nbbytes)
+{
+	memcpy(mtdraw->writebuf + mtdraw->write_fill, src, nbbytes);
+	mtdraw->write_fill += nbbytes;
+}
+
+static ssize_t mtdraw_write(struct cdev *cdev, const void *buf, size_t count,
+			    ulong offset, ulong flags)
+{
+	struct mtdraw *mtdraw = to_mtdraw(cdev);
+	struct mtd_info *mtd = to_mtd(cdev);
+	int bsz = mtd->writesize + mtd->oobsize;
+	ulong numpage;
+	size_t retlen = 0, tofill;
+	int ret = 0;
+
+	if (mtdraw->write_fill &&
+	    mtdraw->write_ofs + mtdraw->write_fill != offset)
+		return -EINVAL;
+	if (mtdraw->write_fill == 0 && offset % bsz)
+		return -EINVAL;
+
+	if (mtdraw->write_fill) {
+		tofill = min_t(size_t, count, bsz - mtdraw->write_fill);
+		mtdraw_fillbuf(mtdraw, buf, tofill);
+		offset += tofill;
+		count -= tofill;
+		retlen += tofill;
+	}
+
+	if (mtdraw->write_fill == bsz) {
+		ret = mtdraw_blkwrite(mtd, mtdraw->writebuf, mtdraw->write_ofs);
+		retlen += ret;
+		mtdraw->write_fill = 0;
+	}
+
+	numpage = offset / (mtd->writesize + mtd->oobsize);
+	while (ret >= 0 && count >= bsz) {
+		ret = mtdraw_blkwrite(mtd, buf + retlen,
+				   mtd->writesize * numpage++);
+		count -= ret;
+		retlen += ret;
+		offset += ret;
+	}
+
+	if (ret >= 0 && count) {
+		mtdraw->write_ofs = offset - mtdraw->write_fill;
+		mtdraw_fillbuf(mtdraw, buf + retlen, count);
+	}
+
+	if (ret < 0) {
+		printf("err %d\n", ret);
+		return ret;
+	} else {
+		return retlen;
+	}
+}
+
+static ssize_t mtdraw_erase(struct cdev *cdev, size_t count, ulong offset)
+{
+	struct mtd_info *mtd = to_mtd(cdev);
+	struct erase_info erase;
+	int ret;
+
+	offset = offset / (mtd->writesize + mtd->oobsize) * mtd->writesize;
+	count = count / (mtd->writesize + mtd->oobsize) * mtd->writesize;
+
+	memset(&erase, 0, sizeof(erase));
+	erase.mtd = mtd;
+	erase.addr = offset;
+	erase.len = mtd->erasesize;
+
+	while (count > 0) {
+		debug("erase %d %d\n", erase.addr, erase.len);
+
+		ret = mtd->block_isbad(mtd, erase.addr);
+		if (ret > 0) {
+			printf("Skipping bad block at 0x%08x\n", erase.addr);
+		} else {
+			ret = mtd->erase(mtd, &erase);
+			if (ret)
+				return ret;
+		}
+
+		erase.addr += mtd->erasesize;
+		count -= count > mtd->erasesize ? mtd->erasesize : count;
+	}
+
+	return 0;
+}
+#else
+static ssize_t mtdraw_write(struct cdev *cdev, const void *buf, size_t count,
+			    ulong offset, ulong flags)
+{
+	return 0;
+}
+static ssize_t mtdraw_erase(struct cdev *cdev, size_t count, ulong offset)
+{
+	return 0;
+}
+#endif
+
+static const struct file_operations mtd_raw_fops = {
+	.read		= mtdraw_read,
+	.write		= mtdraw_write,
+	.erase		= mtdraw_erase,
+	.ioctl		= mtd_ioctl,
+	.lseek		= dev_lseek_default,
+};
+
+static int add_mtdraw_device(struct mtd_info *mtd, char *devname)
+{
+	struct mtdraw *mtdraw;
+
+	mtdraw = xzalloc(sizeof(*mtdraw));
+	mtdraw->writebuf = xmalloc(RAW_WRITEBUF_SIZE);
+	mtdraw->mtd = mtd;
+
+	mtdraw->cdev.ops = (struct file_operations *)&mtd_raw_fops;
+	mtdraw->cdev.size = mtd->size / mtd->writesize *
+		(mtd->writesize + mtd->oobsize);
+	mtdraw->cdev.name = asprintf("%sraw%d", devname, mtd->class_dev.id);
+	mtdraw->cdev.priv = mtdraw;
+	mtdraw->cdev.dev = &mtd->class_dev;
+	mtdraw->cdev.mtd = mtd;
+	devfs_create(&mtdraw->cdev);
+
+	return 0;
+}
+
+static struct mtddev_hook mtdraw_hook = {
+	.add_mtd_device = add_mtdraw_device,
+};
+
+static int __init register_mtdraw(void)
+{
+	mtdcore_add_hook(&mtdraw_hook);
+	return 0;
+}
+
+coredevice_initcall(register_mtdraw);
-- 
1.7.5.4


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