linux-kernel - Re: [PATCH v2] mtd: mtdconcat: Check existence of _read|_write from subdev'master device before assigning

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Message-ID: <8b315831-84c5-38f3-d3b7-bb53f52c28b8@huawei.com>
Date:   Tue, 17 Aug 2021 10:45:55 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     <miquel.raynal@...tlin.com>, <richard@....at>, <vigneshr@...com>,
        <bbrezillon@...nel.org>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <yukuai3@...wei.com>, <sfr@...b.auug.org.au>
Subject: Re: [PATCH v2] mtd: mtdconcat: Check existence of _read|_write from
 subdev'master device before assigning

在 2021/8/17 10:45, Zhihao Cheng 写道:
Hi Miquel,
I found a better way to fix the "WARNING" on _read|_read_oob checking. 
Since sub-mtd device has been registered successfully, we can check 
against the existence of _read|_read_oob callbacks by subdev's master 
device.
BTW, fix missing space between the SHA1 and the subject suggested by 
Stephen.
> Since 2431c4f5b46c3 ("mtd: Implement mtd_{read,write}() as wrappers
> around mtd_{read,write}_oob()") don't allow _write|_read and
> _write_oob|_read_oob existing at the same time. We should check the
> existence of callbacks "_read and _write" from subdev's master device
> (We can trust master device since it has been registered) before
> assigning, otherwise following warning occurs while making
> concatenated device:
>
>    WARNING: CPU: 2 PID: 6728 at drivers/mtd/mtdcore.c:595
>    add_mtd_device+0x7f/0x7b0
>
> Fixes: 2431c4f5b46c3 ("mtd: Implement mtd_{read,write}() around ...")
> Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
> ---
>   drivers/mtd/mtdconcat.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
> index af51eee6b5e8..f685a581df48 100644
> --- a/drivers/mtd/mtdconcat.c
> +++ b/drivers/mtd/mtdconcat.c
> @@ -694,6 +694,10 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
>   		concat->mtd._block_markbad = concat_block_markbad;
>   	if (subdev_master->_panic_write)
>   		concat->mtd._panic_write = concat_panic_write;
> +	if (subdev_master->_read)
> +		concat->mtd._read = concat_read;
> +	if (subdev_master->_write)
> +		concat->mtd._write = concat_write;
>   
>   	concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;
>   
> @@ -755,8 +759,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
>   	concat->mtd.name = name;
>   
>   	concat->mtd._erase = concat_erase;
> -	concat->mtd._read = concat_read;
> -	concat->mtd._write = concat_write;
>   	concat->mtd._sync = concat_sync;
>   	concat->mtd._lock = concat_lock;
>   	concat->mtd._unlock = concat_unlock;