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Message-ID: <9955e32c-615a-f02c-abc3-a7b613bf34ee@huawei.com>
Date: Tue, 10 Aug 2021 19:35:02 +0800
From: Zhihao Cheng <chengzhihao1@...wei.com>
To: Miquel Raynal <miquel.raynal@...tlin.com>
CC: <richard@....at>, <vigneshr@...com>, <bbrezillon@...nel.org>,
<linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
<yukuai3@...wei.com>
Subject: Re: [PATCH 1/2] mtd: mtdconcat: Judge callback function existence
getting from master for each partition
在 2021/8/7 18:32, Miquel Raynal 写道:
Hi Miquel,
> Hi Zhihao,
>
> Zhihao Cheng <chengzhihao1@...wei.com> wrote on Sat, 7 Aug 2021
> 10:15:46 +0800:
>
>> 在 2021/8/7 3:28, Miquel Raynal 写道:
>> Hi Miquel,
>>> Hi Zhihao,
>>>
>>> Zhihao Cheng <chengzhihao1@...wei.com> wrote on Sat, 31 Jul 2021
>>> 10:32:42 +0800:
>>> @@ -721,14 +724,15 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c
>>> subdev[i]->flags & MTD_WRITEABLE;
>>> }
>>> > + subdev_master = mtd_get_master(subdev[i]);
>>> concat->mtd.size += subdev[i]->size;
>>> concat->mtd.ecc_stats.badblocks +=
>>> subdev[i]->ecc_stats.badblocks;
>>> if (concat->mtd.writesize != subdev[i]->writesize ||
>>> concat->mtd.subpage_sft != subdev[i]->subpage_sft ||
>>> concat->mtd.oobsize != subdev[i]->oobsize ||
>>> - !concat->mtd._read_oob != !subdev[i]->_read_oob ||
>>> - !concat->mtd._write_oob != !subdev[i]->_write_oob) {
>>> + !concat->mtd._read_oob != !subdev_master->_read_oob ||
>>> + !concat->mtd._write_oob != !subdev_master->_write_oob) {
>>> Do you really need this change?
>> I think both "!concat->mtd._read_oob != !subdev[i]->_read_oob" and "!concat->mtd._write_oob != !subdev[i]->_write_oob" need to be modified otherwise concatenating goes failure.
>>
>> I thought there exists two problems:
>>
>> 1. Wrong callback fetching in mtd partition device
>>
>> 2. Warning for existence of _read and _read_oob at the same time
>>
>> so I solved them in two steps to make history commit logs a bit clear.
>>
>> Though these two patches can be combined to one.
> No please keep the split.
>
> What I mean here is that I don't think your fix is valid. Maybe we
> should propagate these callbacks as well instead of trying to hack into
> this condition. I don't see why you should check against subdev[i] for
> half of the callbacks and check for subdev_master for the last two.
I have the following understanding of mtd:
1. The existence of mtd partition device's callbacks(what can mtd do,
_read, _write, _read_oob, etc.) is decided by mtd master device. All mtd
common functions (mtd_read, mtd_read_oob) pass master mtd device rather
than partition mtd device as parameter, because nand_chip(initialized as
master mtd device) process requests. So there are two steps in mtd
common function: fetch master mtd device; invoke master mtd devices's
callback and pass in master mtd device.
Propogating callbacks to partition mtd device may bring some
imperfections:
A. No adaptions to mtd common functions: partition mtd device's
callbacks will never be invoked, they are only used to judge whether
assigin concatenated device's callback while concatenating. Looks weird.
@@ -86,6 +86,61 @@ static struct mtd_info *allocate_partition(struct
mtd_info *parent,
child->part.offset = part->offset;
INIT_LIST_HEAD(&child->partitions);
+ if (parent->_read)
+ child->_read = parent->_read;
+ if (parent->_write)
+ child->_write = parent->_write;
[...]
+ if (parent->_read_oob)
+ child->_read_oob = parent->_read_oob;
+ if (parent->_write_oob)
B. Re-import removed partition mtd device's callbacks and adapt mtd
common functions: Current implemention is simplier than the version
before 46b5889cc2c54("mtd: implement proper partition handling").
Adapting mtd common functions is a risky thing, which could effect other
modules, should we do that?
+static int part_read(struct mtd_info *mtd, loff_t from, size_t len,
+ size_t *retlen, u_char *buf)
+{
+ struct mtd_part *part = mtd_to_part(mtd);
+ struct mtd_ecc_stats stats;
+ int res;
+
+ stats = part->parent->ecc_stats;
+ res = part->parent->_read(part->parent, from + part->offset, len,
+ retlen, buf);
+ if (unlikely(mtd_is_eccerr(res)))
+ mtd->ecc_stats.failed +=
+ part->parent->ecc_stats.failed - stats.failed;
+ else
+ mtd->ecc_stats.corrected +=
+ part->parent->ecc_stats.corrected - stats.corrected;
+ return res;
+}
static int mtd_read_oob_std(struct mtd_info *mtd, loff_t from,
struct mtd_oob_ops *ops)
{
- struct mtd_info *master = mtd_get_master(mtd);
int ret;
- from = mtd_get_master_ofs(mtd, from);
- if (master->_read_oob)
- ret = master->_read_oob(master, from, ops);
+ if (mtd->_read_oob)
+ ret = mtd->_read_oob(mtd, from, ops);
else
- ret = master->_read(master, from, ops->len, &ops->retlen,
+ ret = mtd->_read(mtd, from, ops->len, &ops->retlen,
ops->datbuf);
2. Checking against subdev[i] for data members and check against
subdev_master for the callbacks looks weird. I modified it based on the
assumption that partition mtd device' callbacks inherit from master mtd
device but data members(name, size) may not. Maybe I should add some
comment to explain why checking against subdev[i] for data members and
checking against subdev_master for the callbacks.
So, which method is better? Any other method?
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