[PATCH v2 2/2] mtd: mtdconcat: Check _read, _write callbacks existence before assignment

[Miquel Raynal]

On Tue, 2021-08-17 at 11:48:57 UTC, Zhihao Cheng wrote:
> 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 at huawei.com>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel