Re: [PATCH] mtd: remove stale comment in mtd_oob_ops structure

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Boris,

Boris Brezillon <boris.brezillon@bootlin.com> wrote on Tue, 17 Jul 2018
14:25:24 +0200:

> On Sat, 14 Jul 2018 14:32:34 +0200
> Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> 
> > A comment in the kernel doc of the mtd_oob_ops structure tells that it
> > is not possible to write more than one page with OOB. This was
> > probably true at some time in the past but today it is entirely wrong.
> > 
> > As one can see for instance in the nand_do_write_ops() helper available
> > in the NAND core, this implementation called by mtd->_write_oob()
> > simply loops over the pages until everything has been written.
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  include/linux/mtd/mtd.h | 4 ----
> >  1 file changed, 4 deletions(-)
> > 
> > diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
> > index a86c4fa93115..59578aab277a 100644
> > --- a/include/linux/mtd/mtd.h
> > +++ b/include/linux/mtd/mtd.h
> > @@ -66,10 +66,6 @@ struct mtd_erase_region_info {
> >   *		mode = MTD_OPS_PLACE_OOB or MTD_OPS_RAW)
> >   * @datbuf:	data buffer - if NULL only oob data are read/written
> >   * @oobbuf:	oob data buffer
> > - *
> > - * Note, it is allowed to read more than one OOB area at one go, but not write.
> > - * The interface assumes that the OOB write requests program only one page's
> > - * OOB area.  
> 
> Hm, I wouldn't be so prompt at nuking this comment since some
> implementations (like onenand) really have this limitation. How about

Didn't know/see.

> adjusting the comment to reflect the fact that this limitation is
> implementation dependent?
> 
> "
> Note, some MTD drivers do not allow you to write more than one OOB area
> at one go. If you try to do that on such an MTD device, -EINVAL will be
> returned. If you want to make your implementation portable on all kind
> of MTD devices you should split the write request into several
> sub-requests when the request crosses a page boundary.
> "

Fine by me.

However, for a future work, I would think that it's something that we
should handle at MTD level (or even in the onenand driver), not at user
level, and simplify the ABI.


Thanks,
Miquèl