Re: [PATCH v4 3/3] mtd: Remove duplicate checks on mtd_oob_ops parameter

[Miquel RAYNAL <miquel.raynal@free-electrons.com>]

Hello Boris,

On Mon, 8 Jan 2018 23:30:10 +0100
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> On Mon, 8 Jan 2018 23:04:55 +0100
> Miquel RAYNAL <miquel.raynal@free-electrons.com> wrote:
> 
> > Hello Boris,
> > 
> > On Mon,  8 Jan 2018 22:15:42 +0100
> > Boris Brezillon <boris.brezillon@free-electrons.com> wrote:
> >   
> > > Some of the check done in custom ->_read/write_oob()
> > > implementation are already done by the core (in
> > > mtd_check_oob_ops()).    
> > 
> > Not sure this is relevant here as your series introduces changes for
> > the SPI NAND framework, but there are other places where these
> > checks are, IMHO, also redundant and could be removed. The "past
> > end" string when grepped in the MTD folder core returns a few more
> > hits.
> > 
> > In the NAND core:
> >   - nand_do_read_oob()
> >   - nand_read_oob()
> >   - nand_do_write_oob()
> >   - nand_write_oob()  
> 
> That's true for nand_read/write_oob(). The one in nand_do_write_oob()
> is still needed because mtd_check_oob_ops() allows OOB writes
> crossing a page boundary. Finally, I don't see any boundary checks in
> nand_do_read_oob().

I forgot that crossing page boundaries was not a use case of
mtd_check_oob_ops(), thanks for pointing it. However in
nand_do_read/write_oob(), the comment and the code really state the
checked boundary is the end of the device. So are you sure these two
checks are needed?

[1]http://elixir.free-electrons.com/linux/latest/source/drivers/mtd/nand/nand_base.c#L2226
[2]http://elixir.free-electrons.com/linux/latest/source/drivers/mtd/nand/nand_base.c#L2886

> 
> > Maybe also in onenand_base.c, but I am less confident for this one:
> >   - onenand_bbt_read_oob()  
> 
> Unfortunately no, this function is directly called from onenand_bbt.c,
> which means the MTD layer layer is completely bypassed. I also found
> boundary checks in onenand_mlc_read_ops_nolock(), but again, this
> function is called from do_otp_read() which is not going through
> mtd_check_oob_ops().
> 
> > 
> > What do you think?  
> 
> I'll remove the extra checks in nand_read/write_oob(). For the other
> ones, one solution would be to expose mtd_check_oob_ops(), but I'll
> keep that for later.

Ok.

Thanks,
Miquèl