[U-Boot] [PATCH v2 04/21] mtd: Fallback to ->_read/write() when ->_read/write_oob() is missing

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

Hi Boris,

Boris Brezillon <boris.brezillon@bootlin.com> wrote on Thu, 12 Jul 2018
00:20:52 +0200:

> On Wed, 11 Jul 2018 17:25:12 +0200
> Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> 
> > Some MTD sublayers/drivers are implementing ->_read/write() and
> > not ->_read/write_oob().
> > 
> > While for NAND devices both are usually valid, for NOR devices, using
> > the _oob variant has no real meaning. But, as the MTD layer is supposed
> > to hide as much as possible the flash complexity to the user, there is
> > no reason to error out while it is just a matter of rewritting things
> > internally.
> > 
> > Add a fallback on mtd->_read() (resp. mtd->_write()) when the user calls
> > mtd_read_oob() (resp. mtd_write_oob()) while mtd->_read_oob() (resp.
> > mtd->_write_oob) is not implemented. There is already a fallback on the
> > _oob variant if the former is used.  
> 
> Now I'm jealous. Can we have the same thing Linux :-).

U-Boot, one step ahead ;)

> 
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  drivers/mtd/mtdcore.c | 26 ++++++++++++++++++++------
> >  1 file changed, 20 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> > index ba170f212e..095c58cf8c 100644
> > --- a/drivers/mtd/mtdcore.c
> > +++ b/drivers/mtd/mtdcore.c
> > @@ -1048,20 +1048,27 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
> >  {
> >  	int ret_code;
> >  	ops->retlen = ops->oobretlen = 0;
> > -	if (!mtd->_read_oob)
> > -		return -EOPNOTSUPP;
> >  
> >  	ret_code = mtd_check_oob_ops(mtd, from, ops);
> >  	if (ret_code)
> >  		return ret_code;
> >  
> > +	/* Check the validity of a potential fallback on mtd->_read */
> > +	if ((!mtd->_read_oob) && (!mtd->_read || ops->oobbuf))  
> 
> Parens around !mtd->_read_oob are not needed.

[...]

> > -	return mtd->_write_oob(mtd, to, ops);
> > +	/* Check the validity of a potential fallback on mtd->_write */
> > +	if ((!mtd->_write_oob) && (!mtd->_write || ops->oobbuf))  
> 
> Ditto.
> 

Right!

Thanks,
Miquèl