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From: Felix Fietkau <nbd@nbd.name>
Subject: mtd: implement write support for partitions covering only a part of an eraseblock (buffer data that would otherwise be erased)
lede-commit: 87a8e8ac1067f58ba831c4aae443f3655c31cd80
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
drivers/mtd/mtdpart.c | 90 ++++++++++++++++++++++++++++++++++++++++++++-----
include/linux/mtd/mtd.h | 4 +++
2 files changed, 85 insertions(+), 9 deletions(-)
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -36,6 +36,8 @@
#include "mtdcore.h"
#include "mtdsplit/mtdsplit.h"
+#define MTD_ERASE_PARTIAL 0x8000 /* partition only covers parts of an erase block */
+
/* Our partition linked list */
static LIST_HEAD(mtd_partitions);
static DEFINE_MUTEX(mtd_partitions_mutex);
@@ -220,6 +222,53 @@ static int part_erase(struct mtd_info *m
{
struct mtd_part *part = mtd_to_part(mtd);
int ret;
+ size_t wrlen = 0;
+ u8 *erase_buf = NULL;
+ u32 erase_buf_ofs = 0;
+ bool partial_start = false;
+
+ if (mtd->flags & MTD_ERASE_PARTIAL) {
+ size_t readlen = 0;
+ u64 mtd_ofs;
+
+ erase_buf = kmalloc(part->parent->erasesize, GFP_ATOMIC);
+ if (!erase_buf)
+ return -ENOMEM;
+
+ mtd_ofs = part->offset + instr->addr;
+ erase_buf_ofs = do_div(mtd_ofs, part->parent->erasesize);
+
+ if (erase_buf_ofs > 0) {
+ instr->addr -= erase_buf_ofs;
+ ret = mtd_read(part->parent,
+ instr->addr + part->offset,
+ part->parent->erasesize,
+ &readlen, erase_buf);
+
+ instr->len += erase_buf_ofs;
+ partial_start = true;
+ } else {
+ mtd_ofs = part->offset + part->mtd.size;
+ erase_buf_ofs = part->parent->erasesize -
+ do_div(mtd_ofs, part->parent->erasesize);
+
+ if (erase_buf_ofs > 0) {
+ instr->len += erase_buf_ofs;
+ ret = mtd_read(part->parent,
+ part->offset + instr->addr +
+ instr->len - part->parent->erasesize,
+ part->parent->erasesize, &readlen,
+ erase_buf);
+ } else {
+ ret = 0;
+ }
+ }
+ if (ret < 0) {
+ kfree(erase_buf);
+ return ret;
+ }
+
+ }
instr->addr += part->offset;
ret = part->parent->_erase(part->parent, instr);
@@ -227,6 +276,24 @@ static int part_erase(struct mtd_info *m
instr->fail_addr -= part->offset;
instr->addr -= part->offset;
+ if (mtd->flags & MTD_ERASE_PARTIAL) {
+ if (partial_start) {
+ part->parent->_write(part->parent,
+ instr->addr, erase_buf_ofs,
+ &wrlen, erase_buf);
+ instr->addr += erase_buf_ofs;
+ } else {
+ instr->len -= erase_buf_ofs;
+ part->parent->_write(part->parent,
+ instr->addr + instr->len,
+ erase_buf_ofs, &wrlen,
+ erase_buf +
+ part->parent->erasesize -
+ erase_buf_ofs);
+ }
+ kfree(erase_buf);
+ }
+
return ret;
}
@@ -539,19 +606,22 @@ static struct mtd_part *allocate_partiti
remainder = do_div(tmp, wr_alignment);
if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
/* Doesn't start on a boundary of major erase size */
- /* FIXME: Let it be writable if it is on a boundary of
- * _minor_ erase size though */
- slave->mtd.flags &= ~MTD_WRITEABLE;
- printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase/write block boundary -- force read-only\n",
- part->name);
+ slave->mtd.flags |= MTD_ERASE_PARTIAL;
+ if (((u32)slave->mtd.size) > parent->erasesize)
+ slave->mtd.flags &= ~MTD_WRITEABLE;
+ else
+ slave->mtd.erasesize = slave->mtd.size;
}
- tmp = part_absolute_offset(parent) + slave->mtd.size;
+ tmp = part_absolute_offset(parent) + slave->offset + slave->mtd.size;
remainder = do_div(tmp, wr_alignment);
if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
- slave->mtd.flags &= ~MTD_WRITEABLE;
- printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase/write block -- force read-only\n",
- part->name);
+ slave->mtd.flags |= MTD_ERASE_PARTIAL;
+
+ if ((u32)slave->mtd.size > parent->erasesize)
+ slave->mtd.flags &= ~MTD_WRITEABLE;
+ else
+ slave->mtd.erasesize = slave->mtd.size;
}
mtd_set_ooblayout(&slave->mtd, &part_ooblayout_ops);
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