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e07403a8c6
There is a surprisingly large number of tutorials that suggest using mtdblock to mount SquashFS filesystems on flash devices, including NAND devices. This approach is suboptimal than using UBI. If the flash device is NAND, this is specially true, due to wear leveling, bit-flips and badblocks. In this case UBI is strongly preferred, so be nice to users and print a warning suggesting to consider UBI block, if mtdblock is added for a NAND device. Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Link: https://lore.kernel.org/linux-mtd/20210801234509.18774-8-ezequiel@collabora.com
78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Simple read-only (writable only for RAM) mtdblock driver
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*
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* Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org>
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*/
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/mtd/mtd.h>
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#include <linux/mtd/blktrans.h>
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#include <linux/module.h>
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#include <linux/major.h>
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static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
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unsigned long block, char *buf)
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{
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size_t retlen;
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if (mtd_read(dev->mtd, (block * 512), 512, &retlen, buf))
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return 1;
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return 0;
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}
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static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
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unsigned long block, char *buf)
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{
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size_t retlen;
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if (mtd_write(dev->mtd, (block * 512), 512, &retlen, buf))
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return 1;
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return 0;
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}
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static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
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{
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struct mtd_blktrans_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
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if (!dev)
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return;
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dev->mtd = mtd;
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dev->devnum = mtd->index;
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dev->size = mtd->size >> 9;
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dev->tr = tr;
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dev->readonly = 1;
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if (mtd_type_is_nand(mtd))
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pr_warn("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
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tr->name, mtd->name);
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if (add_mtd_blktrans_dev(dev))
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kfree(dev);
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}
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static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
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{
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del_mtd_blktrans_dev(dev);
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}
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static struct mtd_blktrans_ops mtdblock_tr = {
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.name = "mtdblock",
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.major = MTD_BLOCK_MAJOR,
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.part_bits = 0,
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.blksize = 512,
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.readsect = mtdblock_readsect,
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.writesect = mtdblock_writesect,
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.add_mtd = mtdblock_add_mtd,
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.remove_dev = mtdblock_remove_dev,
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.owner = THIS_MODULE,
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};
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module_mtd_blktrans(mtdblock_tr);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
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MODULE_DESCRIPTION("Simple read-only block device emulation access to MTD devices");
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